article on global warming class 7

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What is climate change?

We investigate…, so, what is climate change.

Climate change (or global warming ), is the process of our planet heating up.

Scientists estimate that since the Industrial Revolution , human activity has caused the Earth to warm by approximately 1°C . While that might not sound like much, it means big things for people and wildlife around the globe.

Unfortunately, rising temperatures don’t just mean that we’ll get nicer weather – if only ! The changing climate will actually make our weather more extreme and unpredictable . 

As temperatures rise, some areas will get wetter and lots of animals (and humans!) could find they’re not able to adapt to their changing climate. 

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What causes climate change?

1. burning fossil fuels, 3. deforestation, how will climate change affect the planet.

The Earth has had many tropical climates and ice ages over the billions of years that it’s been in existence, so why is now so different? Well, this is because for the last 150 years human activity has meant we’re releasing a huge amount of harmful gases into the Earth’s atmosphere, and records show that the global temperatures are rising more rapidly since this time. 

A warmer climate could affect our planet in a number of ways:

–  More rainfall

– Changing seasons

– Shrinking sea ice

– Rising sea levels

How will climate change affect wildlife?

It’s not just polar animals who are in trouble. Apes like orangutans , which live in the rainforests of Indonesia , are under threat as their habitat is cut down, and more droughts cause more bushfires.  

How will people be affected by climate change?

Climate change won’t just affect animals, it’s already having an impact on people, too. Most affected are some of the people who grow the food we eat every day. Farming communities, especially in developing countries , are facing higher temperatures, increased rain, floods and droughts.

We Brits love a good cuppa , (around 165 million cups of the stuff every day!), but we probably take for granted just how much work goes into growing our tea. Environmental conditions can affect the flavour and quality plus it needs a very specific rainfall to grow. In Kenya, climate change is making rainfall patterns less and less predictable. Often there will be droughts followed by huge amounts rain, which makes it very difficult to grow tea.

How are people coping with climate change?

Buying Fairtrade products can help make sure a farmer is paid a fair wage. This means they can cover their costs, earn enough money to have a decent standard of living, and invest in their farms to keep their crop healthy, without needing to resort to cheap methods of farming which can further damage the environment.

This support also helps farmers to replace eucalyptus trees –  which take up a lot of water – with indigenous trees that are better for the farmers’ soil. They can learn to make fuel-efficient stoves which will not only make them a little extra money, but also reduce the carbon footprint of the community – cool !

How can I help prevent climate change?

Small changes in your own home can make a difference, too. Try switching to energy-saving lightbulbs, walking instead of using the car, turning off electrical items when you’re not using them, recycling and reducing your food waste.

All these little things can make a difference. You can check out more eco-friendly ideas, in our kids’ guide to saving the planet! Plus, check out our cool article about Greta Thunberg , too, to discover how young people are making their voices heard. 

You can download information about Fairtrade and climate change for your school, here! www.fairtrade.org.uk/schools.  

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What about campaigning for governments to take action to radically reduce dependance on fossil fuels?

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• ENVIRONMENT

What is global warming, explained

The planet is heating up—and fast.

Glaciers are melting , sea levels are rising, cloud forests are dying , and wildlife is scrambling to keep pace. It has become clear that humans have caused most of the past century's warming by releasing heat-trapping gases as we power our modern lives. Called greenhouse gases, their levels are higher now than at any time in the last 800,000 years .

We often call the result global warming, but it is causing a set of changes to the Earth's climate, or long-term weather patterns, that varies from place to place. While many people think of global warming and climate change as synonyms , scientists use “climate change” when describing the complex shifts now affecting our planet’s weather and climate systems—in part because some areas actually get cooler in the short term .

Climate change encompasses not only rising average temperatures but also extreme weather events , shifting wildlife populations and habitats, rising seas , and a range of other impacts. All of those changes are emerging as humans continue to add heat-trapping greenhouse gases to the atmosphere, changing the rhythms of climate that all living things have come to rely on.

What will we do—what can we do—to slow this human-caused warming? How will we cope with the changes we've already set into motion? While we struggle to figure it all out, the fate of the Earth as we know it—coasts, forests, farms, and snow-capped mountains—hangs in the balance.

Understanding the greenhouse effect

The "greenhouse effect" is the warming that happens when certain gases in Earth's atmosphere trap heat . These gases let in light but keep heat from escaping, like the glass walls of a greenhouse, hence the name.

Sunlight shines onto the Earth's surface, where the energy is absorbed and then radiate back into the atmosphere as heat. In the atmosphere, greenhouse gas molecules trap some of the heat, and the rest escapes into space. The more greenhouse gases concentrate in the atmosphere, the more heat gets locked up in the molecules.

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Scientists have known about the greenhouse effect since 1824, when Joseph Fourier calculated that the Earth would be much colder if it had no atmosphere. This natural greenhouse effect is what keeps the Earth's climate livable. Without it, the Earth's surface would be an average of about 60 degrees Fahrenheit (33 degrees Celsius) cooler.

A polar bear stands sentinel on Rudolf Island in Russia’s Franz Josef Land archipelago, where the perennial ice is melting.

In 1895, the Swedish chemist Svante Arrhenius discovered that humans could enhance the greenhouse effect by making carbon dioxide , a greenhouse gas. He kicked off 100 years of climate research that has given us a sophisticated understanding of global warming.

Levels of greenhouse gases have gone up and down over the Earth's history, but they had been fairly constant for the past few thousand years. Global average temperatures had also stayed fairly constant over that time— until the past 150 years . Through the burning of fossil fuels and other activities that have emitted large amounts of greenhouse gases, particularly over the past few decades, humans are now enhancing the greenhouse effect and warming Earth significantly, and in ways that promise many effects , scientists warn.

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Aren't temperature changes natural.

Human activity isn't the only factor that affects Earth's climate. Volcanic eruptions and variations in solar radiation from sunspots, solar wind, and the Earth's position relative to the sun also play a role. So do large-scale weather patterns such as El Niño .

But climate models that scientists use to monitor Earth’s temperatures take those factors into account. Changes in solar radiation levels as well as minute particles suspended in the atmosphere from volcanic eruptions , for example, have contributed only about two percent to the recent warming effect. The balance comes from greenhouse gases and other human-caused factors, such as land use change .

The short timescale of this recent warming is singular as well. Volcanic eruptions , for example, emit particles that temporarily cool the Earth's surface. But their effect lasts just a few years. Events like El Niño also work on fairly short and predictable cycles. On the other hand, the types of global temperature fluctuations that have contributed to ice ages occur on a cycle of hundreds of thousands of years.

For thousands of years now, emissions of greenhouse gases to the atmosphere have been balanced out by greenhouse gases that are naturally absorbed. As a result, greenhouse gas concentrations and temperatures have been fairly stable, which has allowed human civilization to flourish within a consistent climate.

Greenland is covered with a vast amount of ice—but the ice is melting four times faster than thought, suggesting that Greenland may be approaching a dangerous tipping point, with implications for global sea-level rise.

Now, humans have increased the amount of carbon dioxide in the atmosphere by more than a third since the Industrial Revolution. Changes that have historically taken thousands of years are now happening over the course of decades .

Why does this matter?

The rapid rise in greenhouse gases is a problem because it’s changing the climate faster than some living things can adapt to. Also, a new and more unpredictable climate poses unique challenges to all life.

Historically, Earth's climate has regularly shifted between temperatures like those we see today and temperatures cold enough to cover much of North America and Europe with ice. The difference between average global temperatures today and during those ice ages is only about 9 degrees Fahrenheit (5 degrees Celsius), and the swings have tended to happen slowly, over hundreds of thousands of years.

But with concentrations of greenhouse gases rising, Earth's remaining ice sheets such as Greenland and Antarctica are starting to melt too . That extra water could raise sea levels significantly, and quickly. By 2050, sea levels are predicted to rise between one and 2.3 feet as glaciers melt.

As the mercury rises, the climate can change in unexpected ways. In addition to sea levels rising, weather can become more extreme . This means more intense major storms, more rain followed by longer and drier droughts—a challenge for growing crops—changes in the ranges in which plants and animals can live, and loss of water supplies that have historically come from glaciers.

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‘How long before climate change will destroy the Earth?’: research reveals what Australian kids want to know about our warming world

Lecturer and Research Fellow, School of Geography, Planning, and Spatial Sciences. Coordinator, Education for Sustainability Tasmania, University of Tasmania

PhD Candidate, University of Tasmania

Research Fellow in Climate Change Communication, Climate Futures Program, University of Tasmania, and Lecturer in Communication, Deakin University

Professor, at IMAS and Director of the Centre for Marine Socioecology, University of Tasmania

Senior Lecturer in Curriculum and Pedagogy, University of Tasmania

Postdoctoral Research Fellow, Future Ocean and Coastal Infrastructures (FOCI) Consortium, Memorial University, Canada, and Centre for Marine Socioecology, University of Tasmania

Disclosure statement

Chloe Lucas received funding from the Centre for Marine Socioecology, the University of Tasmania, and the Tasmanian Climate Change Office for the research and engagement reported in this article, as part of the Curious Climate Schools program. She is also funded by the Australian Research Council. Chloe is a member of the Centre for Marine Socioecology, the Institute of Australian Geographers and the International Environmental Communication Association, and is a member of the Editorial Board of Australian Geographer.

Charlotte Earl-Jones received funding from the Centre for Marine Socioecology, the University of Tasmania, and the Tasmanian Climate Change Office for the research and engagement reported in this article, as part of the Curious Climate Schools program. She is also funded by Westpac Scholars Trust and the Australian Commonwealth Government Research Training Program. She is a member of the Institute of Australian Geographers.

Gabi Mocatta received funding from the Centre for Marine Socioecology, the University of Tasmania and the Tasmanian Climate Change Office (now re-named Renewables, Climate and Future Industries Tasmania) for the research and engagement reported here. She is also President of the Board of the International Environmental Communication Association.

Gretta Pecl receives funding from the Australian Research Council, Department of Agriculture Water and the Environment, Department of Primary Industries NSW, Department of Premier and Cabinet (Tasmania), the Fisheries Research & Development Corporation, and has received travel funding support from the Australian government for participation in the IPCC process.

Kim Beasy received funding from the Centre for Marine Socioecology, the University of Tasmania, and the Tasmanian Climate Change Office for the research and engagement reported in this article, as part of the Curious Climate School program. She is a member of the Centre of Marine Socioecology and the Australian Association of Environmental Education.

Rachel Kelly receives funding from the Fisheries Research and Development Corporation, and the Centre for Marine Socioecology at the University of Tasmania.

University of Tasmania and Deakin University provide funding as members of The Conversation AU.

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Every day, more children discover they are living in a climate crisis. This makes many children feel sad, anxious, angry, powerless, confused and frightened about what the future holds.

The climate change burden facing young people is inherently unfair. But they have the potential to be the most powerful generation when it comes to creating change.

Research and public debate so far has largely failed to engage with the voices and opinions of children – instead, focusing on the views of adults. Our research set out to change this.

We asked 1,500 children to tell us what they wanted to know about climate change. The results show climate action, rather than the scientific cause of the problem, is their greatest concern. It suggests climate change education in schools must become more holistic and empowering, and children should be given more opportunities to shape the future they will inherit.

Questions of ‘remarkable depth’

In Australia, research shows 43% of children aged 10 to 14 are worried about the future impact of climate change, and one in four believe the world will end before they grow up.

Children are often seen as passive, marginal actors in the climate crisis. Evidence of an intergenerational divide is also emerging. Young people report feeling unheard and betrayed by older generations when it comes to climate change.

Our study examined 464 questions about climate change submitted to the Curious Climate Schools program in Tasmania in 2021 and 2022. The questions were asked by primary and high school students aged 7 to 18.

The children’s questions reveal a remarkable depth of consideration about climate change.

Read more: How well does the new Australian Curriculum prepare young people for climate change?

Kids are thinking globally

The impacts of climate change were discussed in 38% of questions. About 10% of questions asked about impacts on places, such as:

With the rate of climate change, what will the Earth be like when I’m an adult? What does the melting of glaciers in Antarctica mean for Tassie (Tasmania) and our climate?

These questions demonstrate children’s understanding of the global scale of the climate crisis and their concern about places close to home.

How climate change will affect humans accounted for 12% of questions. Impacts on animals and biodiversity were the subject of 9% of questions. Examples include:

Will climate change make us live elsewhere, eg underwater or in space? What species may become extinct due to climate change, which species could adapt to changing conditions and have we already seen this begin to happen?

Approximately 7% of questions asked about ice melting and/or sea-level rise, while 3% asked about extreme weather or disasters.

‘What can we do?’

Action on climate change was the most frequent theme, discussed in 40% of questions. Some questions involved the kinds of action needed and others focused on the challenges in taking action. They include:

How would you make rapid climate improvements without sacrificing industry and finance?

Around 16% of questions asked about, or implied, who was responsible for climate action. Governments and politicians were the largest group singled out. Other questions asked about the responsibilities of schools, communities, states, countries and individuals. Examples include:

What can I do as a 12-year-old to help the planet, and why will these actions help us? If the world knows about climate change, why has not much happened?

Some 20% of questions suggested action by specific sectors of the economy. This included stopping using fossil fuels and moving to renewable energy or nuclear power. Some suggested action related to food, agriculture or fisheries.

Existential worries

In 27% of questions, students raised existential concerns about climate change. This reveals the urgency and frustration many children feel.

The largest group of these questions (15%) asked for predictions of future events. Some 5% of questions implied the planet, or humanity, was doomed. They included:

Will all the reefs die? How long before climate change will destroy the Earth? How long will we be able to survive on our planet if we do nothing to try to slow down/reverse climate change?

Why is Earth getting hot?

Scientific questions about climate change made up 25% of the total. The largest group related to the causes and physical processes, such as:

What causes the Earth to get hotter due to climate change? Would our world be the same now if the Industrial Revolution hadn’t happened? How do they know the climate and percentage of gases, such as methane, in the 1800s?

What all this means

Our analysis indicates children are very concerned about how climate change affects the things and places they care about. Children also want to know how to contribute to solutions – either through their own actions or influencing adults, industries and governments. Children asked fewer questions about the scientific evidence for climate change.

So what are the implications of this?

Research shows that where climate change is taught in schools, it is primarily represented as a scientific and environmental issue, without focus on the social and political causes and challenges.

While children need information about the science of global warming, our research suggests this is not enough. Climate change should be integrated into all subjects in the curriculum, from social studies to maths to food.

Teachers should also be trained to understand climate challenges themselves, and to identify and support students suffering from climate distress.

And children must be given opportunities to get involved in shaping the future. Governments and industry should commit to listening to children’s concerns about climate change, and acting on them.

Read more: 'I tend to be very gentle': how teachers are navigating climate change in the classroom

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• Young people
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• Climate impacts

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The Science of Climate Change Explained: Facts, Evidence and Proof

Definitive answers to the big questions.

Credit... Photo Illustration by Andrea D'Aquino

Supported by

By Julia Rosen

Ms. Rosen is a journalist with a Ph.D. in geology. Her research involved studying ice cores from Greenland and Antarctica to understand past climate changes.

• Published April 19, 2021 Updated Nov. 6, 2021

The science of climate change is more solid and widely agreed upon than you might think. But the scope of the topic, as well as rampant disinformation, can make it hard to separate fact from fiction. Here, we’ve done our best to present you with not only the most accurate scientific information, but also an explanation of how we know it.

How do we know climate change is really happening?

How much agreement is there among scientists about climate change, do we really only have 150 years of climate data how is that enough to tell us about centuries of change, how do we know climate change is caused by humans, since greenhouse gases occur naturally, how do we know they’re causing earth’s temperature to rise, why should we be worried that the planet has warmed 2°f since the 1800s, is climate change a part of the planet’s natural warming and cooling cycles, how do we know global warming is not because of the sun or volcanoes, how can winters and certain places be getting colder if the planet is warming, wildfires and bad weather have always happened. how do we know there’s a connection to climate change, how bad are the effects of climate change going to be, what will it cost to do something about climate change, versus doing nothing.

Climate change is often cast as a prediction made by complicated computer models. But the scientific basis for climate change is much broader, and models are actually only one part of it (and, for what it’s worth, they’re surprisingly accurate ).

For more than a century , scientists have understood the basic physics behind why greenhouse gases like carbon dioxide cause warming. These gases make up just a small fraction of the atmosphere but exert outsized control on Earth’s climate by trapping some of the planet’s heat before it escapes into space. This greenhouse effect is important: It’s why a planet so far from the sun has liquid water and life!

However, during the Industrial Revolution, people started burning coal and other fossil fuels to power factories, smelters and steam engines, which added more greenhouse gases to the atmosphere. Ever since, human activities have been heating the planet.

We know this is true thanks to an overwhelming body of evidence that begins with temperature measurements taken at weather stations and on ships starting in the mid-1800s. Later, scientists began tracking surface temperatures with satellites and looking for clues about climate change in geologic records. Together, these data all tell the same story: Earth is getting hotter.

Average global temperatures have increased by 2.2 degrees Fahrenheit, or 1.2 degrees Celsius, since 1880, with the greatest changes happening in the late 20th century. Land areas have warmed more than the sea surface and the Arctic has warmed the most — by more than 4 degrees Fahrenheit just since the 1960s. Temperature extremes have also shifted. In the United States, daily record highs now outnumber record lows two-to-one.

Where it was cooler or warmer in 2020 compared with the middle of the 20th century

This warming is unprecedented in recent geologic history. A famous illustration, first published in 1998 and often called the hockey-stick graph, shows how temperatures remained fairly flat for centuries (the shaft of the stick) before turning sharply upward (the blade). It’s based on data from tree rings, ice cores and other natural indicators. And the basic picture , which has withstood decades of scrutiny from climate scientists and contrarians alike, shows that Earth is hotter today than it’s been in at least 1,000 years, and probably much longer.

In fact, surface temperatures actually mask the true scale of climate change, because the ocean has absorbed 90 percent of the heat trapped by greenhouse gases . Measurements collected over the last six decades by oceanographic expeditions and networks of floating instruments show that every layer of the ocean is warming up. According to one study , the ocean has absorbed as much heat between 1997 and 2015 as it did in the previous 130 years.

We also know that climate change is happening because we see the effects everywhere. Ice sheets and glaciers are shrinking while sea levels are rising. Arctic sea ice is disappearing. In the spring, snow melts sooner and plants flower earlier. Animals are moving to higher elevations and latitudes to find cooler conditions. And droughts, floods and wildfires have all gotten more extreme. Models predicted many of these changes, but observations show they are now coming to pass.

Back to top .

There’s no denying that scientists love a good, old-fashioned argument. But when it comes to climate change, there is virtually no debate: Numerous studies have found that more than 90 percent of scientists who study Earth’s climate agree that the planet is warming and that humans are the primary cause. Most major scientific bodies, from NASA to the World Meteorological Organization , endorse this view. That’s an astounding level of consensus given the contrarian, competitive nature of the scientific enterprise, where questions like what killed the dinosaurs remain bitterly contested .

Scientific agreement about climate change started to emerge in the late 1980s, when the influence of human-caused warming began to rise above natural climate variability. By 1991, two-thirds of earth and atmospheric scientists surveyed for an early consensus study said that they accepted the idea of anthropogenic global warming. And by 1995, the Intergovernmental Panel on Climate Change, a famously conservative body that periodically takes stock of the state of scientific knowledge, concluded that “the balance of evidence suggests that there is a discernible human influence on global climate.” Currently, more than 97 percent of publishing climate scientists agree on the existence and cause of climate change (as does nearly 60 percent of the general population of the United States).

So where did we get the idea that there’s still debate about climate change? A lot of it came from coordinated messaging campaigns by companies and politicians that opposed climate action. Many pushed the narrative that scientists still hadn’t made up their minds about climate change, even though that was misleading. Frank Luntz, a Republican consultant, explained the rationale in an infamous 2002 memo to conservative lawmakers: “Should the public come to believe that the scientific issues are settled, their views about global warming will change accordingly,” he wrote. Questioning consensus remains a common talking point today, and the 97 percent figure has become something of a lightning rod .

To bolster the falsehood of lingering scientific doubt, some people have pointed to things like the Global Warming Petition Project, which urged the United States government to reject the Kyoto Protocol of 1997, an early international climate agreement. The petition proclaimed that climate change wasn’t happening, and even if it were, it wouldn’t be bad for humanity. Since 1998, more than 30,000 people with science degrees have signed it. However, nearly 90 percent of them studied something other than Earth, atmospheric or environmental science, and the signatories included just 39 climatologists. Most were engineers, doctors, and others whose training had little to do with the physics of the climate system.

A few well-known researchers remain opposed to the scientific consensus. Some, like Willie Soon, a researcher affiliated with the Harvard-Smithsonian Center for Astrophysics, have ties to the fossil fuel industry . Others do not, but their assertions have not held up under the weight of evidence. At least one prominent skeptic, the physicist Richard Muller, changed his mind after reassessing historical temperature data as part of the Berkeley Earth project. His team’s findings essentially confirmed the results he had set out to investigate, and he came away firmly convinced that human activities were warming the planet. “Call me a converted skeptic,” he wrote in an Op-Ed for the Times in 2012.

Mr. Luntz, the Republican pollster, has also reversed his position on climate change and now advises politicians on how to motivate climate action.

A final note on uncertainty: Denialists often use it as evidence that climate science isn’t settled. However, in science, uncertainty doesn’t imply a lack of knowledge. Rather, it’s a measure of how well something is known. In the case of climate change, scientists have found a range of possible future changes in temperature, precipitation and other important variables — which will depend largely on how quickly we reduce emissions. But uncertainty does not undermine their confidence that climate change is real and that people are causing it.

Earth’s climate is inherently variable. Some years are hot and others are cold, some decades bring more hurricanes than others, some ancient droughts spanned the better part of centuries. Glacial cycles operate over many millenniums. So how can scientists look at data collected over a relatively short period of time and conclude that humans are warming the planet? The answer is that the instrumental temperature data that we have tells us a lot, but it’s not all we have to go on.

Historical records stretch back to the 1880s (and often before), when people began to regularly measure temperatures at weather stations and on ships as they traversed the world’s oceans. These data show a clear warming trend during the 20th century.

Global average temperature compared with the middle of the 20th century

+0.75°C

–0.25°

Some have questioned whether these records could be skewed, for instance, by the fact that a disproportionate number of weather stations are near cities, which tend to be hotter than surrounding areas as a result of the so-called urban heat island effect. However, researchers regularly correct for these potential biases when reconstructing global temperatures. In addition, warming is corroborated by independent data like satellite observations, which cover the whole planet, and other ways of measuring temperature changes.

Much has also been made of the small dips and pauses that punctuate the rising temperature trend of the last 150 years. But these are just the result of natural climate variability or other human activities that temporarily counteract greenhouse warming. For instance, in the mid-1900s, internal climate dynamics and light-blocking pollution from coal-fired power plants halted global warming for a few decades. (Eventually, rising greenhouse gases and pollution-control laws caused the planet to start heating up again.) Likewise, the so-called warming hiatus of the 2000s was partly a result of natural climate variability that allowed more heat to enter the ocean rather than warm the atmosphere. The years since have been the hottest on record .

Still, could the entire 20th century just be one big natural climate wiggle? To address that question, we can look at other kinds of data that give a longer perspective. Researchers have used geologic records like tree rings, ice cores, corals and sediments that preserve information about prehistoric climates to extend the climate record. The resulting picture of global temperature change is basically flat for centuries, then turns sharply upward over the last 150 years. It has been a target of climate denialists for decades. However, study after study has confirmed the results , which show that the planet hasn’t been this hot in at least 1,000 years, and probably longer.

Scientists have studied past climate changes to understand the factors that can cause the planet to warm or cool. The big ones are changes in solar energy, ocean circulation, volcanic activity and the amount of greenhouse gases in the atmosphere. And they have each played a role at times.

For example, 300 years ago, a combination of reduced solar output and increased volcanic activity cooled parts of the planet enough that Londoners regularly ice skated on the Thames . About 12,000 years ago, major changes in Atlantic circulation plunged the Northern Hemisphere into a frigid state. And 56 million years ago, a giant burst of greenhouse gases, from volcanic activity or vast deposits of methane (or both), abruptly warmed the planet by at least 9 degrees Fahrenheit, scrambling the climate, choking the oceans and triggering mass extinctions.

In trying to determine the cause of current climate changes, scientists have looked at all of these factors . The first three have varied a bit over the last few centuries and they have quite likely had modest effects on climate , particularly before 1950. But they cannot account for the planet’s rapidly rising temperature, especially in the second half of the 20th century, when solar output actually declined and volcanic eruptions exerted a cooling effect.

That warming is best explained by rising greenhouse gas concentrations . Greenhouse gases have a powerful effect on climate (see the next question for why). And since the Industrial Revolution, humans have been adding more of them to the atmosphere, primarily by extracting and burning fossil fuels like coal, oil and gas, which releases carbon dioxide.

Bubbles of ancient air trapped in ice show that, before about 1750, the concentration of carbon dioxide in the atmosphere was roughly 280 parts per million. It began to rise slowly and crossed the 300 p.p.m. threshold around 1900. CO2 levels then accelerated as cars and electricity became big parts of modern life, recently topping 420 p.p.m . The concentration of methane, the second most important greenhouse gas, has more than doubled. We’re now emitting carbon much faster than it was released 56 million years ago .

30 billion metric tons

Carbon dioxide emitted worldwide 1850-2017

Rest of world

Other developed

European Union

Developed economies

Other countries

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E.U. and U.K.

These rapid increases in greenhouse gases have caused the climate to warm abruptly. In fact, climate models suggest that greenhouse warming can explain virtually all of the temperature change since 1950. According to the most recent report by the Intergovernmental Panel on Climate Change, which assesses published scientific literature, natural drivers and internal climate variability can only explain a small fraction of late-20th century warming.

Another study put it this way: The odds of current warming occurring without anthropogenic greenhouse gas emissions are less than 1 in 100,000 .

But greenhouse gases aren’t the only climate-altering compounds people put into the air. Burning fossil fuels also produces particulate pollution that reflects sunlight and cools the planet. Scientists estimate that this pollution has masked up to half of the greenhouse warming we would have otherwise experienced.

Greenhouse gases like water vapor and carbon dioxide serve an important role in the climate. Without them, Earth would be far too cold to maintain liquid water and humans would not exist!

Here’s how it works: the planet’s temperature is basically a function of the energy the Earth absorbs from the sun (which heats it up) and the energy Earth emits to space as infrared radiation (which cools it down). Because of their molecular structure, greenhouse gases temporarily absorb some of that outgoing infrared radiation and then re-emit it in all directions, sending some of that energy back toward the surface and heating the planet . Scientists have understood this process since the 1850s .

Greenhouse gas concentrations have varied naturally in the past. Over millions of years, atmospheric CO2 levels have changed depending on how much of the gas volcanoes belched into the air and how much got removed through geologic processes. On time scales of hundreds to thousands of years, concentrations have changed as carbon has cycled between the ocean, soil and air.

Today, however, we are the ones causing CO2 levels to increase at an unprecedented pace by taking ancient carbon from geologic deposits of fossil fuels and putting it into the atmosphere when we burn them. Since 1750, carbon dioxide concentrations have increased by almost 50 percent. Methane and nitrous oxide, other important anthropogenic greenhouse gases that are released mainly by agricultural activities, have also spiked over the last 250 years.

We know based on the physics described above that this should cause the climate to warm. We also see certain telltale “fingerprints” of greenhouse warming. For example, nights are warming even faster than days because greenhouse gases don’t go away when the sun sets. And upper layers of the atmosphere have actually cooled, because more energy is being trapped by greenhouse gases in the lower atmosphere.

We also know that we are the cause of rising greenhouse gas concentrations — and not just because we can measure the CO2 coming out of tailpipes and smokestacks. We can see it in the chemical signature of the carbon in CO2.

Carbon comes in three different masses: 12, 13 and 14. Things made of organic matter (including fossil fuels) tend to have relatively less carbon-13. Volcanoes tend to produce CO2 with relatively more carbon-13. And over the last century, the carbon in atmospheric CO2 has gotten lighter, pointing to an organic source.

We can tell it’s old organic matter by looking for carbon-14, which is radioactive and decays over time. Fossil fuels are too ancient to have any carbon-14 left in them, so if they were behind rising CO2 levels, you would expect the amount of carbon-14 in the atmosphere to drop, which is exactly what the data show .

It’s important to note that water vapor is the most abundant greenhouse gas in the atmosphere. However, it does not cause warming; instead it responds to it . That’s because warmer air holds more moisture, which creates a snowball effect in which human-caused warming allows the atmosphere to hold more water vapor and further amplifies climate change. This so-called feedback cycle has doubled the warming caused by anthropogenic greenhouse gas emissions.

A common source of confusion when it comes to climate change is the difference between weather and climate. Weather is the constantly changing set of meteorological conditions that we experience when we step outside, whereas climate is the long-term average of those conditions, usually calculated over a 30-year period. Or, as some say: Weather is your mood and climate is your personality.

So while 2 degrees Fahrenheit doesn’t represent a big change in the weather, it’s a huge change in climate. As we’ve already seen, it’s enough to melt ice and raise sea levels, to shift rainfall patterns around the world and to reorganize ecosystems, sending animals scurrying toward cooler habitats and killing trees by the millions.

It’s also important to remember that two degrees represents the global average, and many parts of the world have already warmed by more than that. For example, land areas have warmed about twice as much as the sea surface. And the Arctic has warmed by about 5 degrees. That’s because the loss of snow and ice at high latitudes allows the ground to absorb more energy, causing additional heating on top of greenhouse warming.

Relatively small long-term changes in climate averages also shift extremes in significant ways. For instance, heat waves have always happened, but they have shattered records in recent years. In June of 2020, a town in Siberia registered temperatures of 100 degrees . And in Australia, meteorologists have added a new color to their weather maps to show areas where temperatures exceed 125 degrees. Rising sea levels have also increased the risk of flooding because of storm surges and high tides. These are the foreshocks of climate change.

And we are in for more changes in the future — up to 9 degrees Fahrenheit of average global warming by the end of the century, in the worst-case scenario . For reference, the difference in global average temperatures between now and the peak of the last ice age, when ice sheets covered large parts of North America and Europe, is about 11 degrees Fahrenheit.

Under the Paris Climate Agreement, which President Biden recently rejoined, countries have agreed to try to limit total warming to between 1.5 and 2 degrees Celsius, or 2.7 and 3.6 degrees Fahrenheit, since preindustrial times. And even this narrow range has huge implications . According to scientific studies, the difference between 2.7 and 3.6 degrees Fahrenheit will very likely mean the difference between coral reefs hanging on or going extinct, and between summer sea ice persisting in the Arctic or disappearing completely. It will also determine how many millions of people suffer from water scarcity and crop failures, and how many are driven from their homes by rising seas. In other words, one degree Fahrenheit makes a world of difference.

Earth’s climate has always changed. Hundreds of millions of years ago, the entire planet froze . Fifty million years ago, alligators lived in what we now call the Arctic . And for the last 2.6 million years, the planet has cycled between ice ages when the planet was up to 11 degrees cooler and ice sheets covered much of North America and Europe, and milder interglacial periods like the one we’re in now.

Climate denialists often point to these natural climate changes as a way to cast doubt on the idea that humans are causing climate to change today. However, that argument rests on a logical fallacy. It’s like “seeing a murdered body and concluding that people have died of natural causes in the past, so the murder victim must also have died of natural causes,” a team of social scientists wrote in The Debunking Handbook , which explains the misinformation strategies behind many climate myths.

Indeed, we know that different mechanisms caused the climate to change in the past. Glacial cycles, for example, were triggered by periodic variations in Earth’s orbit , which take place over tens of thousands of years and change how solar energy gets distributed around the globe and across the seasons.

These orbital variations don’t affect the planet’s temperature much on their own. But they set off a cascade of other changes in the climate system; for instance, growing or melting vast Northern Hemisphere ice sheets and altering ocean circulation. These changes, in turn, affect climate by altering the amount of snow and ice, which reflect sunlight, and by changing greenhouse gas concentrations. This is actually part of how we know that greenhouse gases have the ability to significantly affect Earth’s temperature.

For at least the last 800,000 years , atmospheric CO2 concentrations oscillated between about 180 parts per million during ice ages and about 280 p.p.m. during warmer periods, as carbon moved between oceans, forests, soils and the atmosphere. These changes occurred in lock step with global temperatures, and are a major reason the entire planet warmed and cooled during glacial cycles, not just the frozen poles.

Today, however, CO2 levels have soared to 420 p.p.m. — the highest they’ve been in at least three million years . The concentration of CO2 is also increasing about 100 times faster than it did at the end of the last ice age. This suggests something else is going on, and we know what it is: Since the Industrial Revolution, humans have been burning fossil fuels and releasing greenhouse gases that are heating the planet now (see Question 5 for more details on how we know this, and Questions 4 and 8 for how we know that other natural forces aren’t to blame).

Over the next century or two, societies and ecosystems will experience the consequences of this climate change. But our emissions will have even more lasting geologic impacts: According to some studies, greenhouse gas levels may have already warmed the planet enough to delay the onset of the next glacial cycle for at least an additional 50,000 years.

The sun is the ultimate source of energy in Earth’s climate system, so it’s a natural candidate for causing climate change. And solar activity has certainly changed over time. We know from satellite measurements and other astronomical observations that the sun’s output changes on 11-year cycles. Geologic records and sunspot numbers, which astronomers have tracked for centuries, also show long-term variations in the sun’s activity, including some exceptionally quiet periods in the late 1600s and early 1800s.

We know that, from 1900 until the 1950s, solar irradiance increased. And studies suggest that this had a modest effect on early 20th century climate, explaining up to 10 percent of the warming that’s occurred since the late 1800s. However, in the second half of the century, when the most warming occurred, solar activity actually declined . This disparity is one of the main reasons we know that the sun is not the driving force behind climate change.

Another reason we know that solar activity hasn’t caused recent warming is that, if it had, all the layers of the atmosphere should be heating up. Instead, data show that the upper atmosphere has actually cooled in recent decades — a hallmark of greenhouse warming .

So how about volcanoes? Eruptions cool the planet by injecting ash and aerosol particles into the atmosphere that reflect sunlight. We’ve observed this effect in the years following large eruptions. There are also some notable historical examples, like when Iceland’s Laki volcano erupted in 1783, causing widespread crop failures in Europe and beyond, and the “ year without a summer ,” which followed the 1815 eruption of Mount Tambora in Indonesia.

Since volcanoes mainly act as climate coolers, they can’t really explain recent warming. However, scientists say that they may also have contributed slightly to rising temperatures in the early 20th century. That’s because there were several large eruptions in the late 1800s that cooled the planet, followed by a few decades with no major volcanic events when warming caught up. During the second half of the 20th century, though, several big eruptions occurred as the planet was heating up fast. If anything, they temporarily masked some amount of human-caused warming.

The second way volcanoes can impact climate is by emitting carbon dioxide. This is important on time scales of millions of years — it’s what keeps the planet habitable (see Question 5 for more on the greenhouse effect). But by comparison to modern anthropogenic emissions, even big eruptions like Krakatoa and Mount St. Helens are just a drop in the bucket. After all, they last only a few hours or days, while we burn fossil fuels 24-7. Studies suggest that, today, volcanoes account for 1 to 2 percent of total CO2 emissions.

When a big snowstorm hits the United States, climate denialists can try to cite it as proof that climate change isn’t happening. In 2015, Senator James Inhofe, an Oklahoma Republican, famously lobbed a snowball in the Senate as he denounced climate science. But these events don’t actually disprove climate change.

While there have been some memorable storms in recent years, winters are actually warming across the world. In the United States, average temperatures in December, January and February have increased by about 2.5 degrees this century.

On the flip side, record cold days are becoming less common than record warm days. In the United States, record highs now outnumber record lows two-to-one . And ever-smaller areas of the country experience extremely cold winter temperatures . (The same trends are happening globally.)

So what’s with the blizzards? Weather always varies, so it’s no surprise that we still have severe winter storms even as average temperatures rise. However, some studies suggest that climate change may be to blame. One possibility is that rapid Arctic warming has affected atmospheric circulation, including the fast-flowing, high-altitude air that usually swirls over the North Pole (a.k.a. the Polar Vortex ). Some studies suggest that these changes are bringing more frigid temperatures to lower latitudes and causing weather systems to stall , allowing storms to produce more snowfall. This may explain what we’ve experienced in the U.S. over the past few decades, as well as a wintertime cooling trend in Siberia , although exactly how the Arctic affects global weather remains a topic of ongoing scientific debate .

Climate change may also explain the apparent paradox behind some of the other places on Earth that haven’t warmed much. For instance, a splotch of water in the North Atlantic has cooled in recent years, and scientists say they suspect that may be because ocean circulation is slowing as a result of freshwater streaming off a melting Greenland . If this circulation grinds almost to a halt, as it’s done in the geologic past, it would alter weather patterns around the world.

Not all cold weather stems from some counterintuitive consequence of climate change. But it’s a good reminder that Earth’s climate system is complex and chaotic, so the effects of human-caused changes will play out differently in different places. That’s why “global warming” is a bit of an oversimplification. Instead, some scientists have suggested that the phenomenon of human-caused climate change would more aptly be called “ global weirding .”

Extreme weather and natural disasters are part of life on Earth — just ask the dinosaurs. But there is good evidence that climate change has increased the frequency and severity of certain phenomena like heat waves, droughts and floods. Recent research has also allowed scientists to identify the influence of climate change on specific events.

Let’s start with heat waves . Studies show that stretches of abnormally high temperatures now happen about five times more often than they would without climate change, and they last longer, too. Climate models project that, by the 2040s, heat waves will be about 12 times more frequent. And that’s concerning since extreme heat often causes increased hospitalizations and deaths, particularly among older people and those with underlying health conditions. In the summer of 2003, for example, a heat wave caused an estimated 70,000 excess deaths across Europe. (Human-caused warming amplified the death toll .)

Climate change has also exacerbated droughts , primarily by increasing evaporation. Droughts occur naturally because of random climate variability and factors like whether El Niño or La Niña conditions prevail in the tropical Pacific. But some researchers have found evidence that greenhouse warming has been affecting droughts since even before the Dust Bowl . And it continues to do so today. According to one analysis , the drought that afflicted the American Southwest from 2000 to 2018 was almost 50 percent more severe because of climate change. It was the worst drought the region had experienced in more than 1,000 years.

Rising temperatures have also increased the intensity of heavy precipitation events and the flooding that often follows. For example, studies have found that, because warmer air holds more moisture, Hurricane Harvey, which struck Houston in 2017, dropped between 15 and 40 percent more rainfall than it would have without climate change.

It’s still unclear whether climate change is changing the overall frequency of hurricanes, but it is making them stronger . And warming appears to favor certain kinds of weather patterns, like the “ Midwest Water Hose ” events that caused devastating flooding across the Midwest in 2019 .

It’s important to remember that in most natural disasters, there are multiple factors at play. For instance, the 2019 Midwest floods occurred after a recent cold snap had frozen the ground solid, preventing the soil from absorbing rainwater and increasing runoff into the Missouri and Mississippi Rivers. These waterways have also been reshaped by levees and other forms of river engineering, some of which failed in the floods.

Wildfires are another phenomenon with multiple causes. In many places, fire risk has increased because humans have aggressively fought natural fires and prevented Indigenous peoples from carrying out traditional burning practices. This has allowed fuel to accumulate that makes current fires worse .

However, climate change still plays a major role by heating and drying forests, turning them into tinderboxes. Studies show that warming is the driving factor behind the recent increases in wildfires; one analysis found that climate change is responsible for doubling the area burned across the American West between 1984 and 2015. And researchers say that warming will only make fires bigger and more dangerous in the future.

It depends on how aggressively we act to address climate change. If we continue with business as usual, by the end of the century, it will be too hot to go outside during heat waves in the Middle East and South Asia . Droughts will grip Central America, the Mediterranean and southern Africa. And many island nations and low-lying areas, from Texas to Bangladesh, will be overtaken by rising seas. Conversely, climate change could bring welcome warming and extended growing seasons to the upper Midwest , Canada, the Nordic countries and Russia . Farther north, however, the loss of snow, ice and permafrost will upend the traditions of Indigenous peoples and threaten infrastructure.

It’s complicated, but the underlying message is simple: unchecked climate change will likely exacerbate existing inequalities . At a national level, poorer countries will be hit hardest, even though they have historically emitted only a fraction of the greenhouse gases that cause warming. That’s because many less developed countries tend to be in tropical regions where additional warming will make the climate increasingly intolerable for humans and crops. These nations also often have greater vulnerabilities, like large coastal populations and people living in improvised housing that is easily damaged in storms. And they have fewer resources to adapt, which will require expensive measures like redesigning cities, engineering coastlines and changing how people grow food.

Already, between 1961 and 2000, climate change appears to have harmed the economies of the poorest countries while boosting the fortunes of the wealthiest nations that have done the most to cause the problem, making the global wealth gap 25 percent bigger than it would otherwise have been. Similarly, the Global Climate Risk Index found that lower income countries — like Myanmar, Haiti and Nepal — rank high on the list of nations most affected by extreme weather between 1999 and 2018. Climate change has also contributed to increased human migration, which is expected to increase significantly .

Even within wealthy countries, the poor and marginalized will suffer the most. People with more resources have greater buffers, like air-conditioners to keep their houses cool during dangerous heat waves, and the means to pay the resulting energy bills. They also have an easier time evacuating their homes before disasters, and recovering afterward. Lower income people have fewer of these advantages, and they are also more likely to live in hotter neighborhoods and work outdoors, where they face the brunt of climate change.

These inequalities will play out on an individual, community, and regional level. A 2017 analysis of the U.S. found that, under business as usual, the poorest one-third of counties, which are concentrated in the South, will experience damages totaling as much as 20 percent of gross domestic product, while others, mostly in the northern part of the country, will see modest economic gains. Solomon Hsiang, an economist at University of California, Berkeley, and the lead author of the study, has said that climate change “may result in the largest transfer of wealth from the poor to the rich in the country’s history.”

Even the climate “winners” will not be immune from all climate impacts, though. Desirable locations will face an influx of migrants. And as the coronavirus pandemic has demonstrated, disasters in one place quickly ripple across our globalized economy. For instance, scientists expect climate change to increase the odds of multiple crop failures occurring at the same time in different places, throwing the world into a food crisis .

On top of that, warmer weather is aiding the spread of infectious diseases and the vectors that transmit them, like ticks and mosquitoes . Research has also identified troubling correlations between rising temperatures and increased interpersonal violence , and climate change is widely recognized as a “threat multiplier” that increases the odds of larger conflicts within and between countries. In other words, climate change will bring many changes that no amount of money can stop. What could help is taking action to limit warming.

One of the most common arguments against taking aggressive action to combat climate change is that doing so will kill jobs and cripple the economy. But this implies that there’s an alternative in which we pay nothing for climate change. And unfortunately, there isn’t. In reality, not tackling climate change will cost a lot , and cause enormous human suffering and ecological damage, while transitioning to a greener economy would benefit many people and ecosystems around the world.

Let’s start with how much it will cost to address climate change. To keep warming well below 2 degrees Celsius, the goal of the Paris Climate Agreement, society will have to reach net zero greenhouse gas emissions by the middle of this century. That will require significant investments in things like renewable energy, electric cars and charging infrastructure, not to mention efforts to adapt to hotter temperatures, rising sea-levels and other unavoidable effects of current climate changes. And we’ll have to make changes fast.

Estimates of the cost vary widely. One recent study found that keeping warming to 2 degrees Celsius would require a total investment of between $4 trillion and $60 trillion, with a median estimate of $16 trillion, while keeping warming to 1.5 degrees Celsius could cost between $10 trillion and $100 trillion, with a median estimate of $30 trillion. (For reference, the entire world economy was about $88 trillion in 2019.) Other studies have found that reaching net zero will require annual investments ranging from less than 1.5 percent of global gross domestic product to as much as 4 percent . That’s a lot, but within the range of historical energy investments in countries like the U.S.

Now, let’s consider the costs of unchecked climate change, which will fall hardest on the most vulnerable. These include damage to property and infrastructure from sea-level rise and extreme weather, death and sickness linked to natural disasters, pollution and infectious disease, reduced agricultural yields and lost labor productivity because of rising temperatures, decreased water availability and increased energy costs, and species extinction and habitat destruction. Dr. Hsiang, the U.C. Berkeley economist, describes it as “death by a thousand cuts.”

As a result, climate damages are hard to quantify. Moody’s Analytics estimates that even 2 degrees Celsius of warming will cost the world $69 trillion by 2100, and economists expect the toll to keep rising with the temperature. In a recent survey , economists estimated the cost would equal 5 percent of global G.D.P. at 3 degrees Celsius of warming (our trajectory under current policies) and 10 percent for 5 degrees Celsius. Other research indicates that, if current warming trends continue, global G.D.P. per capita will decrease between 7 percent and 23 percent by the end of the century — an economic blow equivalent to multiple coronavirus pandemics every year. And some fear these are vast underestimates .

Already, studies suggest that climate change has slashed incomes in the poorest countries by as much as 30 percent and reduced global agricultural productivity by 21 percent since 1961. Extreme weather events have also racked up a large bill. In 2020, in the United States alone, climate-related disasters like hurricanes, droughts, and wildfires caused nearly $100 billion in damages to businesses, property and infrastructure, compared to an average of $18 billion per year in the 1980s.

Given the steep price of inaction, many economists say that addressing climate change is a better deal . It’s like that old saying: an ounce of prevention is worth a pound of cure. In this case, limiting warming will greatly reduce future damage and inequality caused by climate change. It will also produce so-called co-benefits, like saving one million lives every year by reducing air pollution, and millions more from eating healthier, climate-friendly diets. Some studies even find that meeting the Paris Agreement goals could create jobs and increase global G.D.P . And, of course, reining in climate change will spare many species and ecosystems upon which humans depend — and which many people believe to have their own innate value.

The challenge is that we need to reduce emissions now to avoid damages later, which requires big investments over the next few decades. And the longer we delay, the more we will pay to meet the Paris goals. One recent analysis found that reaching net-zero by 2050 would cost the U.S. almost twice as much if we waited until 2030 instead of acting now. But even if we miss the Paris target, the economics still make a strong case for climate action, because every additional degree of warming will cost us more — in dollars, and in lives.

Veronica Penney contributed reporting.

Illustration photographs by Esther Horvath, Max Whittaker, David Maurice Smith and Talia Herman for The New York Times; Esther Horvath/Alfred-Wegener-Institut

An earlier version of this article misidentified the authors of The Debunking Handbook. It was written by social scientists who study climate communication, not a team of climate scientists.

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The Greenhouse Effect and our Planet

The greenhouse effect happens when certain gases, which are known as greenhouse gases, accumulate in Earth’s atmosphere. Greenhouse gases include carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O), ozone (O 3 ), and fluorinated gases.

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Earth keeps getting warmer. Scientists believe this is caused by an increase in something called greenhouse gases .

Greenhouse gases collect in Earth's atmosphere . The atmosphere is a layer of gases that surround Earth.  Carbon dioxide (CO 2 ), methane (CH 4 ), and ozone (O 3 ), are kinds of greenhouse gases.

The greenhouse gases allow the sun's light to shine onto Earth's surface. Some of that heat gets reflected . It bounces from the surface of Earth. Then, the gases trap the heat inside Earth. The gases act like the glass walls of a greenhouse. In other words, they are warming.

Animals and Plants Contribute to Greenhouse Gases Without the greenhouse effect , Earth's average temperature would drop. Now, it is about 57 degrees Fahrenheit (14 degrees Celsius). It could drop to as low as 0 degrees Fahrenheit (minus 18 degrees Celsius). The weather would go from mild to very cold.

Some greenhouse gases come from nature. Animals and plants release carbon dioxide when they breathe. Methane is another greenhouse gas . It is released when soil and living things break down.  Volcanoes also release greenhouse gases .

Factories and Vehicles Can also Be Blamed The Industrial Revolution happened in the late 1700s and early 1800s. This led to more factories and machines being built. The factories burned fuel and released more greenhouse gases into the atmosphere.

Greenhouse gases almost doubled between 1970 and 2004.

The amount of CO 2 in the atmosphere is growing. There is more CO 2 now than Earth has seen over the last 650,000 years.

Much of the CO 2 comes from burning fossil fuels . Cars, trains and planes all burn fossil fuels, such as gasoline. Many electric power plants do as well.

More Gases Lead to Global Warming Humans also release CO 2 into the atmosphere when they cut down forests . Trees contain large amounts of carbon.

People add methane to the atmosphere through farming of livestock such as cows. It also happens when we mine for coal .

Fluorinated gases are also greenhouse gases . Chlorofluoro carbons (CFCs) are one example of these. CFCs are used in refrigerators, air conditioners and aerosol cans .

As greenhouse gases increase, so does Earth's temperature. This rise caused by humans is known as global warming.

The Greenhouse Effect and Climate Change Even small increases in temperatures can have huge effects.

Perhaps the biggest effect is that glaciers and ice caps melt faster than usual. The meltwater d rains into the oceans . This causes sea levels to rise.

Glaciers and ice caps cover about one-tenth of the world's land. If all this ice melted, sea levels would rise about 70 meters (230 feet).

Climate scientists say that the world's sea level has risen.

Rising sea levels cause flooding in coastal cities. This could force millions of people in lower-lying areas out of their homes.

Millions of more people in countries depend on water from melted glaciers . They use it for drinking and watering crops . Losing these glaciers would greatly hurt those countries.

Greenhouse gases also cause changes in rain and snow .

In the 1900s, rain and snow increased in eastern parts of North and South America. It also increased in Northern Europe, and northern and Central Asia. However, it decreased in parts of Africa and southern Asia.

As climates change, so do environments . Animals that are used to a certain climate could become threatened.

Many humans depend on predictable rain patterns. This helps them to grow specific crops. If the climate of an area changes, the people there may no longer be able to grow anything. Some of them depend on farming for survival.

What Can We Do?

• Drive less. Use  public transportation , carpool, walk, or ride a bike.
• Fly less. Airplanes produce huge amounts of greenhouse gas emissions.
• Reduce, reuse, and  recycle .
• Plant a tree. Trees absorb carbon dioxide, keeping it out of the atmosphere.
• Use less  electricity .
• Eat less meat. Cows are one of the biggest methane producers.
• Support alternative energy sources that don’t burn fossil fuels.

Artificial Gas

Chlorofluorocarbons (CFCs) are the only greenhouse gases not created by nature. They are created through refrigeration and aerosol cans.

CFCs, used mostly as refrigerants, are chemicals that were developed in the late 19th century and came into wide use in the mid-20th century.

Other greenhouse gases, such as carbon dioxide, are emitted by human activity, at an unnatural and unsustainable level, but the molecules do occur naturally in Earth's atmosphere.

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Global warming or climate change has today become a major threat to the mankind. The Earth’s temperature is on the rise and there are various reasons for it such as greenhouse gases emanating from carbon dioxide ($CO_2$) emissions, burning of fossil fuels or deforestation. 

Impact of Greenhouse Gases

The rise in the levels of carbon dioxide ($CO_2$) leads to substantial increase in temperature. It is because $CO_2$ remains concentrated in the atmosphere for even hundreds of years. Due to activities like fossil fuel combustion for electricity generation, transportation, and heating, human beings have contributed to increase in the $CO_2$ concentration in the atmosphere.

Global Warming: A Gradual Phenomenon

Recent years have been unusually warm, causing worldwide concern. But the fact is that the increase in carbon dioxide actually began in 1800, due to the deforestation of a large chunk of North-eastern American, besides forested parts of the world. The things became worse with emissions in the wake of the industrial revolution, leading to increase in carbon dioxide level by 1900.

Cause of Concern

According to the Intergovernmental Panel on Climate Change (IPCC), global temperature is likely to rise by about 1-3.5 Celsius by the year 2100. It has also suggested that the climate might warm by as much as 10 degrees Fahrenheit over the next 100 years.

Impact of Global Warming

The sea levels are constantly rising as fresh water marshlands, low-lying cities, and islands have been inundated with seawater.

There have been changes in rainfall patterns, leading to droughts and fires in some areas, and flooding in other areas.

Ice caps are constantly melting posing a threat to polar bears as their feeding season stands reduced.

Glaciers are gradually melting.

Animal populations are gradually vanishing as there has been a widespread loss of their habitat.

As per Kyoto protocol, developed countries are required to cut back their emissions. There is a need to reduce coal-fired electricity, increase energy efficiency through wind and solar power, and also high efficiency natural gas generation

Earth's Changing Climate

Climate change is a long-term shift in global or regional climate patterns. Often climate change refers specifically to the rise in global temperatures from the mid 20th century to present.

Earth Science, Geography, Human Geography, Physical Geography

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Climate is the long-term pattern of weather in a particular area. Weather can change from hour to hour, day to day, month to month or even from year to year. Climate refers to what the weather is generally like over 30 years or more. A desert might experience a rainy week, but over the long term, it receives very little rainfall . It has a dry climate .

Living things adjust to climates. Polar bears ( Ursus maritimus ) have adjusted to stay warm in polar climates . Over time, cacti have evolved to hold onto water in dry climates. The number of different kinds of life on Earth is partially due to the number of different climates.

Climates do change. They just change very slowly, over hundreds or even thousands of years. As climates change, organisms that live in the area must adjust, relocate , or risk dying out.

Earth's climate has changed many times. For example, fossils from the Cretaceous period (144 million to 65 million years ago) show that Earth was much warmer than it is today. Breadfruit ( Artocarpus altilis —also called "jackfruit"—trees are now found on tropical islands . However, millions of years ago they even grew on Greenland.

Earth has also experienced several major ice ages . There have been at least four in the past 500,000 years. During these periods, Earth's temperature decreased , causing ice sheets and glaciers to expand. The most recent ice age began about two million years ago and only started ending about 18,000 years ago.

Warmer temperatures have caused the glaciers to shrink. The glaciers have not disappeared completely, however—they still exist in Antarctica and Greenland. Scientists think we live in an " interglacial period ," or a time between glaciers. They have gone away somewhat for now, but hundreds of years from now, the glaciers may grow again.

Scientists who study climate look for proof of past climate change in many different places. Like clumsy criminals, glaciers leave many clues behind. They scratch and rub rocks as they move. They leave little bits of material behind known as "glacial till ." This sometimes forms mounds or ridges. Glaciers also form long, oval-shaped hills. If you see a piece of land with any of these signs, it suggests that a glacier was once there.

Some types of rocks only form from materials left behind from glaciers. When scientists find these rocks, it tells them that glaciers were once there.

Scientists also have proof of glaciers from fossils . Fossils show what kinds of animals and plants lived in certain areas. Looking for fossils of animals that lived in the cold can show scientists how far across the planet the glaciers reached.

Climate changes happen over shorter periods, as well. For example, there was a " Little Ice Age " that lasted only a few hundred years. It peaked during the 1500s and 1600s. During this time, average temperatures around the world were two to three degrees Fahrenheit cooler (about one to 1.5 degrees Celsius) than they are today. A change of one or two degrees might not seem like much, but it was enough to cause major changes. Glaciers grew larger and sometimes engulfed whole mountain villages. Winters were longer than usual, limiting the growing seasons of crops . In northern Europe, people left their farms and villages to avoid starving.

One way scientists have learned about the Little Ice Age is by studying the rings of trees. The thickness of tree rings is related to how much the tree grew each year. During times when it was very dry or very cold, trees could not grow as much and rings would be closer together.

Some climate changes are almost predictable . El Niño , which means "The Child" in Spanish, is a good example of this. El Niño refers to the warming of the surface waters in the Pacific Ocean around the equator . In normal years, winds blow across the ocean from east to west. This drags warm water along in the same direction.

Every few years, normal winds change and ocean currents reverse. This is El Niño . Warm water deepens in the eastern Pacific, near South America. This, in turn, produces big climate changes . Rain decreases in Australia and southern Asia, and crazy storms may pound Pacific islands and the west coast of the Americas. Within a year or two, El Niño ends, and climate systems return to normal.

Natural Causes of Climate Change

Climate changes happen for many reasons. Some of these reasons have to do with Earth's atmosphere . The climate change brought by El Niño , which relies on winds and ocean currents , is an example of natural changes in the atmosphere .

Natural climate change can also be affected by forces outside Earth's atmosphere . Earth's relationship to the sun also affects climate . This includes how Earth is tilted and how it orbits around the sun. These change slowly over time and affect how much of the sun's light reaches different parts of the world at different times. The 100,000-year cycles of ice ages are most likely caused by changes in these things.

Large meteorites hitting Earth could also cause climate change . If a meteor hit Earth, it would send millions of tons of dirt and dust into the atmosphere . This would block some of the sun's rays, making it cold and dark. Many plants and animals would die. Many paleontologists believe that dinosaurs went extinct partially due to a meteor or comet hitting Earth. Dinosaurs could not survive in a cool, dark climate . Their bodies could not adjust to the cold, and the dark killed many plants that they ate. Without the plants , the plant -eating dinosaurs died. And without those plant -eating dinosaurs , the dinosaurs that ate them died too.

Plate tectonics also play a role in climate changes . Earth is made of many layers. The top part is the crust, and just beneath that is the mantle. Together, these make up the "plates" in plate tectonics . We now know there are 15 major plates that cover the planet's surface. They move about as fast as our fingernails grow.

Earth's continental plates have moved a great deal over time. More than 200 million years ago, the continents were merged together as one giant landmass called Pangaea . As the continents broke apart and moved, their positions on Earth changed. The movements of ocean currents also changed. Both of these changes affected climate .

Another cause of climate change is called the greenhouse effect . The greenhouse effect happens when gases like carbon dioxide trap the sun's heat in the atmosphere . Gases that do this are called greenhouse gases . They keep Earth warm. Without any greenhouse gases in the atmosphere , most life on Earth would freeze to death. However, adding too much of these gases to the atmosphere slowly makes the planet warmer.

Human Causes of Climate Change

Some human activities release greenhouse gases . For example, humans burn fossil fuels such as coal , oil and natural gas . People often use them for transportation and electricity . Burning fossil fuels releases greenhouse gases , like carbon dioxide . Trees soak up carbon dioxide , so cutting down forests also adds to the greenhouse effect . Factories send greenhouse gases into the atmosphere too.

Many scientists are worried that these activities are causing dangerous changes in Earth's climate . Average temperatures around the world have risen since about 1880. The seven warmest years of the 1900s happened in the 1990s. This warming trend may be a sign that the greenhouse effect is increasing because of human activity. This is often referred to as " global warming ." It is estimated that humans have increased the amount of carbon dioxide in the atmosphere by about 30 percent in the past 150 years.

Other greenhouse gases are increasing, as well. Methane is an example. Methane is a greenhouse gas produced by rotting plants and animals . As populations grow, they use more goods and throw away more. Large landfills , filled with rotting waste, release tons of methane into the atmosphere .

Some chemicals that are used in refrigeration, air conditioning, and aerosol sprays are also greenhouse gases. Many countries are working to get rid of them. Some have laws to prevent companies from manufacturing them.

Global Warming

As the amount of greenhouse gases in the atmosphere rises, so does the temperature of Earth. Scientists worry that the temperature will increase so much that ice caps will begin seriously melting within the next several decades . This would cause the sea level to rise. Coastal areas and small islands would be flooded. Severe climate change may bring more severe weather patterns . This could include more hurricanes , typhoons , and tornadoes . More rain and snow would fall in some places and far less in others. Places where crops now grow could become deserts .

As climates change, so do the homes for many living things. Animals may not be able to survive in their current homes. Many human societies depend on specific crops for food , clothing, and trade . If the climate of an area changes, the same crops may not grow. Some scientists worry that as the planet warms, tropical diseases will spread further.

The temperature will continue to rise unless steps are taken to stop it. Most scientists agree that we must reduce the amount of greenhouse gases released into the atmosphere. There are many ways to do this, including:

• Drive less. Use public transportation , carpool , walk, or ride a bike.
• Fly less. Airplanes produce huge amounts of greenhouse gas emissions .
• Reduce, reuse, and recycle.
• Plant a tree. Trees soak up carbon dioxide, keeping it out of the atmosphere.
• Use less electricity.
• Eat less meat. Cows are one of the biggest methane producers.
• Support alternative power sources that don't burn fossil fuels. These include power that comes from the sun and from wind.

The climate has changed many times during Earth's history. However, those changes have happened slowly, over thousands of years. Only since the Industrial Revolution have human activities begun to influence climate. Scientists are still working to understand what the consequences might be.

Cool Warming Could the current phase of climate change cause another Little Ice Age? As strange as it sounds, some scientists believe it could. If melting glaciers release large amounts of freshwater into the oceans, this could disrupt the ocean conveyor belt, an important circulation system that moves seawater around the globe. Stopping this cycle could possibly cause cooling of 3 to 5 degrees Celsius (5-9 degrees Fahrenheit) in the ocean and atmosphere.

Early Squirrels The North American red squirrel has started breeding earlier in the year as a result of climate change. Food becomes available to the squirrels earlier because of warmer winters.

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FREE K-12 standards-aligned STEM

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• TeachEngineering
• Global Climate Change

Lesson Global Climate Change

Grade Level: 7 (6-8)

Time Required: 15 minutes

Lesson Dependency: None

Subject Areas: Earth and Space, Science and Technology

NGSS Performance Expectations:

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Curriculum in this Unit Units serve as guides to a particular content or subject area. Nested under units are lessons (in purple) and hands-on activities (in blue). Note that not all lessons and activities will exist under a unit, and instead may exist as "standalone" curriculum.

• Dress for Success
• Building a Barometer
• Weather Alert
• Backyard Weather Station
• Protecting Our City with Levees
• Trash to Treasure!

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Engineering connection, learning objectives, worksheets and attachments, more curriculum like this, introduction/motivation, associated activities, lesson closure, vocabulary/definitions, user comments & tips.

Engineers affect our planet in every design decision they make, from the choice of materials they use to the energy needed for their designs. For example, environmental engineers design products that aim to directly improve the environment, such as designing remediation systems to clean up a toxic spill. All engineers must have a global awareness in the design process and an understanding of how their decision can impact global climate change.

After this lesson, students should be able to:

• Describe the greenhouse effect and global warming.
• Explain the concept of climate change.
• Consider the effects of climate change on extreme weather.
• Recognize ways that they can lower their impact on the environment at home.

Educational Standards Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards. All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN) , a project of D2L (www.achievementstandards.org). In the ASN, standards are hierarchically structured: first by source; e.g. , by state; within source by type; e.g. , science or mathematics; within type by subtype, then by grade, etc .

Ngss: next generation science standards - science, common core state standards - math.

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State standards, colorado - math, colorado - science.

Greenhouse gases (including CO 2 , water vapor and aerosols) are found in the atmosphere above the surface of the Earth. Their job is to trap heat reflected off the Earth from the Sun. You have probably experienced the greenhouse effect while sitting in a car that is parked in the Sun. The glass windows let in light but keep heat from escaping. If it is a bit chilly out, it may feel nice to get into a warm car, but on a hot day, it can be very uncomfortable to get inside a car that is rapidly warming up in the hot Sun. (You may even open the doors and let some of the hot air escape before getting in the car.)

What are some ways that you think global warming might affect people? (Give students a moment to write down and/or share their answers.) It is difficult to predict how global warming influences extreme weather events — such as hurricanes, tsunamis, and tornados, but we can be fairly certain that a warmer atmosphere will at least result in a greater number of extreme heat waves. More rain may be a result as well. Just as a puddle will disappear by evaporating more quickly on a hot summer day, a warmer planet allows more evaporation to occur resulting in more moisture in the atmosphere. This can lead to more frequent and heavier storms when that added moisture is released back onto the surface of the planet. Many scientists believe Hurricane Katrina, which hit the Gulf Coast in August 2005, was stronger due to the warmer waters it traveled over in the Gulf of Mexico, which caused more water to be evaporated into the storm clouds.

Our sea level has already risen 4-8 inches (10-20 cm) during the past century. Some scientists believe that if global warming continues, and our glaciers continue to melt adding more water into the ocean waters, that rising sea levels could flood coastal areas sending millions of inhabitants out of their homes around the world, all within this century. Can you imagine if coastal cities such as New York and San Francisco were underwater?!

Lesson Background and Concepts for Teachers

A worldwide effort, the Kyoto Protocol, is taking steps to limit the amount of greenhouses gases being released into the atmosphere by alloting a certain amount of allowed pollution (or "pollution credits") to every industrialized/developed country (except the U.S. who is not participating). Companies that have cut back on the amount of greenhouse gases they are releasing may sell their "pollution credits" to other companies who are over their allowed amount. For example, if one company is given 10 credits, and they only release 8 credits worth of greenhouses gases into the air, they can sell the other 2 credits to another company who is polluting over their limit.

Many scientists and engineers believe that human activity has contributed to global cliimate change, and that we can prevent it by limiting our output of greenhouse gases. What human activities create greenhouse gases? Most of it comes from burning fossil fuels (such as oil, gas and coal) for energy to light our houses, drive our cars, and manufacture products such as paper, plastics, computers, skateboards and packaged foods. Everything that we buy requires some form of energy to create it and then be made available for us to purchase it. Most of this energy comes from burning fuels such as coal and oil. Burning these fuels releases greenhouse gases, such as carbon dioxide. Greenhouse gases are sent into the air every time a new product is manufactured, and even more greenhouse gases are released into landfills as these products are thrown away. Landfill gas (LFG), naturally produced by the decomposition of organic materials in landfills, contains mostly methane and carbon dioxide — both of which are greenhouse gases that contribute to global warming. How can humans make small steps to reduce the amount of waste that ends up in landfills? Challenge students to design and build products made entirely from reused materials with the associated activity, Trash to Treasure!

Watch this activity on YouTube

Much of our daily human activities directly or indirectly contribute to increasing greenhouse gases, which contribute to global warming. Engineers can help reduce the emission of harmful greenhouse gases by designing products that limit the production of these harmful gases.

climate: The average weather (usually taken over a 30-year time period) for a particular region and time period; the average pattern of weather for a particular region; climatic elements include precipitation, temperature, humidity, sunshine, wind velocity, and phenomena, such as fog, frost and hail storms.

climate change: The change in long-term weather patterns; changes can cause warmer or colder temperatures; annual amounts of rainfall or snowfall can increase or decrease.

global warming: Refers to an average increase in the Earth's temperature, which in turn causes changes in climate; a warmer Earth may lead to changes in rainfall patterns, a rise in sea level, and a wide range of impacts on plants, wildlife, and humans.

greenhouse effect: The effect produced as greenhouse gases allow energy from the sun to pass through the Earth's atmosphere, but prevent most of the outgoing heat from the surface and lower atmosphere from escaping into outer space.

greenhouse gas: Any gas that absorbs the sun's heat in the atmosphere, including water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), halogenated fluorocarbons (HCFCs), ozone (O3), perfluorinated carbons (PFCs), and hydrofluorocarbons (HFCs).

Pre-Lesson Assessment

Stop and Jot: Ask students to write down some ideas they have for ways to help the environment. After a few minutes, have them share their ideas. Some ideas include:

• Walk or ride your bike when possible.
• Turn off the TV, radio, computer and other electronics when not in use.
• Buy recycled products.
• Plant a tree.
• Avoid buying products with a lot of packaging.
• Turn the heat and air conditioning down; just a couple of degrees can make a big difference.
• Replace light bulbs with energy efficient CFLs that use 60% less energy.

Questions: Have students come up with questions to ask eachother about global warming (i.e., what factors have caused the rise in global temperatures over the past century?). After the lesson, have students answer the questions.

Post-Introduction Assessment

Question/Answer: Ask the students a question and instruct them to raise their hands to respond; discuss their answers as a class:

• Can anyone think of other ways that a warmer planet may affect us besides just having hotter temperatures? (Possible answers: More rainfall in some areas, drought in some areas, heavier storms, higher sea levels, crops that no longer grow in certain locations, changes in our ecosystems, etc.)

Lesson Summary Assessment

Brainstorming: As a class, have students engage in open discussion. Remind them that in brainstorming, no idea or suggestion is "silly." All ideas should be respectfully heard. Take an uncritical position, encourage wild ideas and discourage criticism of ideas. Have students raise their hands to respond. Write their ideas on the board. Ask the students:

• What can you do to cut down the amount of greenhouse gases that you are contributing to the atmosphere?

Group Discussion/Presentation: With the class divided into groups of four students each, ask students to design posters that answer the following questions. Have teams present their posters in front of the class.

• What is global warming?
• What is causing global warming?
• How does global warming affect you?
• What can engineers do to prevent or slow down global warming?

Carbon Footprint Worksheet: Ask the students to take home the Carbon Footprint Worksheet and fill it out with their parents based on their family's energy use.

After completion of the worksheets, as a class compute the class mean footprint and discuss why some students have larger or smaller numbers.

Lesson Extension Activities

Have students complete one of the activities described in the U.S. Department of Energy's online teacher's toolbox as developed by the Atmospheric Radiation Measurement Program (ARMP); see: https://www.arm.gov/resources/outreach .

Students observe teacher-led demonstrations, and build and evaluate simple models to understand the greenhouse effect, the role of increased greenhouse gas concentration in global warming, and the implications of global warming for engineers, themselves and the Earth. In an associated literacy activ...

Students determine their carbon footprints by answering questions about their everyday lifestyle choices. Then they engineer plans to reduce them.

Students learn about climate change and what affects it. Students learn a basic understanding of the greenhouse effect, the carbon cycle, global warming, and how transportation can contribute to global warming. Students work together to understand how various forms of transportation have costs and b...

Students learn the concepts of climate change and how cars can contribute to climate change. Students learn the basics of the greenhouse effect and the carbon cycle. They also learn how transportation affects our atmosphere. Students work together to understand how various forms of transportation ha...

U.S. Department of Energy, Office of Science, Atmospheric Radiation Measurement Program, "Bringing Climate Change into the Classroom." ARM Education Program, North Slope of Alaska, 2002, October 28, 2008, accessed June 22, 2009. http://www.arm.gov/news/education/post/16864

U.S. Environmental Protection Agency, Climate Change Kids Site, October 30, 2008, accessed June 22, 2009. http://epa.gov/globalwarming/kids/

"Greenhouse Effect," October 23, 2006, accessed June 22, 2009. http://www.epa.gov/globalwarming/kids/greenhouse.html

U.S. Environmental Protection Agency, Global Warming – Climate, January 7, 2000, accessed June 22, 2009. http://www.epa.gov/climatechange/

Contributors

Supporting program, acknowledgements.

The contents of these digital library curricula were developed by the Integrated Teaching and Learning Program under National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the National Science Foundation, and you should not assume endorsement by the federal government.

Last modified: July 9, 2020

America’s Climate Boomtowns Are Waiting

Rising temperatures could push millions of people north.

As my airplane flew low over the flatlands of western Michigan on a dreary December afternoon, sunbursts splintered the soot-toned clouds and made mirrors out of the flooded fields below. There was plenty of rain in this part of the Rust Belt—sometimes too much. Past the endless acres, I could make out the eastern shore of Lake Michigan, then soon, in the other direction, the Detroit River, Lakes Huron and Erie, and southern Canada. In a world running short on fresh water in its lakes and rivers, more than 20 percent of that water was right here. From a climate standpoint, there couldn’t be a safer place in the country—no hurricanes, no sea-level rise, not much risk of wildfires. That explains why models suggest many more people will soon arrive here.

My destination was the working-class city of Ypsilanti, and a meeting with Beth Gibbons, an urban planner and specialist in climate adaptation. Gibbons served as the founding executive director of a planning consortium called the American Society of Adaptation Professionals (ASAP), which was formed in part to consider how the country could anticipate and prepare for large-scale American climate migration. Gibbons believes that sooner or later a growing chunk of the nation’s population will be arriving in the Great Lakes region. Ypsilanti was an interesting place for us to meet: Many Black migrants from the South had moved here in the 20th century, and during World War II, some were employed building military aircraft. Now the city stands to be transformed again, this time by a great climate migration.

Across the Great Lakes region, cities were in their prime six decades ago as America forged its industrial might. But places such as Detroit, Milwaukee, Cleveland, Buffalo, and Duluth have been in a steady decline ever since. And Ypsilanti, with its nest of underutilized streets, relatively cheap housing, and sprawling industrial spaces still belying the fact that its population peaked in 1970, is little different. That means—at least in theory—these cities have, in a word favored by planning types and scientists, “capacity” for more people.

Read: Every coastal home is now a stick of dynamite

As climate change brings disasters and increasingly unlivable conditions to growing swaths of the United States, it also has the potential to remake America’s economic landscape: Extreme heat, drought, and fires in the South and West could present an opportunity for much of the North. Tens of millions of Americans may move in response to these changes, fleeing coasts and the countryside for larger cities and more temperate climates. In turn, the extent to which our planet’s crisis can present an economic opportunity, or even reimagining, will largely depend on where people wind up, and the ways in which they are welcomed or scorned.

Gibbons, who now works at the climate consulting firm Farallon Strategies, sees Michigan’s future in the Californians unsettled by wildfire. Those people are going to move somewhere. And so they should be persuaded to come to Michigan, she says, before they move to places like Phoenix or Austin. The Great Lakes region should market itself as a climate refuge, she thinks, and then build an economy that makes use of its attributes: the value of its water, its land, its relative survivability. In her vision, small northern cities, invigorated by growing populations, somehow manage to blossom into bigger, greener, cleaner ones.

“There’s no future in which many, many people don’t head here,” Gibbons told me. The only question is whether “we don’t just end up being surprised by it.” And so Gibbons wants to see the Great Lakes states recruit people from around the country, as they did during the Great Migration. Back then, recruiters spread across the South to convince Black people there that opportunity awaited them in the factories of the North: That’s what helped make Ypsilanti.

Today, long after the bomber factory was reduced to weed-riddled expanses of abandoned pavement, the town lives on. This time, the Great Lakes’ water is what will persuade people to move here: Humans have long migrated in pursuit of fresh water. Temperature will also make Michigan an attractive destination for climate migrants. For the coldest places, global warming promises newfound productivity and economic growth. The research connecting economic activity to cool temperatures suggests that there is an optimum climate for human productivity, and as ideal conditions for humans shift northward, some places may soon find themselves smack in the middle of it. The same research suggests that when that happens, people are bound to follow.

These are the findings of Marshall Burke, the deputy director of the Center for Food Security and the Environment at Stanford University. A notable 2015 paper he co-authored in the journal Nature earned international attention for predicting that most countries will see their economies shrivel with climate change. Less noticed, however, was what Burke found would happen on the northern side of that line: Incredible growth could await those places soon to enter their climate prime. Canada, Scandinavia, Iceland, and Russia could see their per capita gross domestic products double or even quadruple.

The United States is on the cusp of this dividing line between economic loss and fortune—its southern regions more imperiled, its northern latitudes much better positioned to capitalize on climate change. Proprietary climate models from the Rhodium Group, an environmental- and economic-research firm I collaborated with for this book , forecast that even as commercial crop yields free-fall across the Great Plains, Texas, and the South, those closer to the Canadian border will steadily increase. By as soon as 2040, yields in North Dakota could jump by 5 to 12 percent. In Minnesota and Wisconsin and northern New York, the rise could be closer to 12 percent. By the end of the century, should climate change be severe, those increases could jump by 24 to 30 percent. Shaded on Rhodium’s map, the data show a dark hot spot where agricultural improvements will far outpace anywhere else in the country. It is centered like a bull’s-eye right over the Great Lakes.

Read: Climate change is already rejiggering where Americans live

Indeed, big commercial agricultural companies and other land investors may already be anticipating this. Over the past several years, land values have skyrocketed across the upper Midwest, as buyers including Bill Gates have snatched up thousands of acres of farmland. To the south, they see the Ogallala Aquifer being depleted, and in California, regulatory mandates potentially reducing water consumption in the Central Valley by 40 to 50 percent, while in northern Michigan, there is more water than anyone knows what to do with.

The Rust Belt arguably led America’s industrial revolution, and with the push of new government support, this same region could help lead a green revolution. The Inflation Reduction Act, President Joe Biden’s historic climate legislation, has promised roughly $370 billion in subsidies for electric vehicles and clean energy, an injection of cash that has already spurred many billions more in private investment and revitalized the country’s manufacturing base. As of late last year, Michigan was the third-largest recipient of that investment. Following the IRA incentives, automakers have collectively invested tens of billions of dollars in the electric-vehicle supply-chain, and the federal government has made some $2 billion in grants available to retrofit and modernize old factories to produce electric vehicles.

Imagine the economic center of gravity of the United States shifting north, and the seesaw effects of that change on the geographic locus of American society. Consider again the lasting cultural implications—for music and arts and sports and labor—of the previous century’s Great Migration out of the South, and what doubling it could mean. One day, a high-speed rail line may race across the Dakotas, through Idaho’s up-and-coming wine country and the country’s new bread basket, to the megalopolis of Seattle, which will have grown so big as people move north that it has nearly merged with Vancouver, at the southern edge of Canada. Never mind that roughly half the country will likely have to experience total upheaval or extreme discomfort—or both—to arrive at this point, or the fact that by the time the Great Lakes region reaches its apex, much of the nation’s southern half will have withered. And of course, every place in America will experience dramatic change and disruption from warming—just look at Canada’s wildfires last summer. But the northern part of the U.S. is more shielded from the primary threats of sea-level rise, hurricanes, drought, and extreme heat. The vision amounts to what Beth Gibbons describes as a chance to shift the climate narrative away from one of exclusive failure. And it suggests that the displacement erupting from climate stress in some places will put others on track toward greater security, wealth, and prosperity.

Read: Vermont was supposed to be a climate haven

An economic boom projected for warming regions, though, Burke told me, will also likely depend on a growing population in the region, which means peacefully resettling large numbers of climate migrants. That’s easier said than done. In Ann Arbor, an affluent city hoping and preparing for climate-driven population growth, I talked with the city’s sustainability director, who counted herself with Beth Gibbons among the optimists. She told me she thought Ann Arbor could be turned into a climate destination, but she was surprised to find that even in her hyperliberal, upper-class college town, some people didn’t necessarily want that.

Gibbons, too, was running into resistance at every turn. Michigan’s Native American tribes, corralled into a tiny sovereign territory, told ASAP focus groups that they see climate change not only affecting their hunting and fishing grounds but potentially bringing new people and economic forces into conflict with their tribal rights. Rural communities from northern Wisconsin to Michigan’s Upper Peninsula fear something similar; the migration during the coronavirus pandemic showed them how little newly relocated second-home owners are simpatico with longtime locals who depend on harvesting timber and working large farms to make a living.

Elsewhere in the United States climate migration is already leading to rising tensions between old and new, as smaller communities confront incoming numbers and rapidly urbanize. The seemingly best places have begun to attract the wealthiest and most mobile to resettle, even while the worst consequences of climate change in the U.S. disproportionately affect minorities and the poor. In Michigan, even some progressives worry that climate migration today will amount to climate gentrification; not so far down the line, forced migration could instead yield fears of newcomers as economic burdens.

Migration can be thought of as the decision to leave, the choice of where to go, and the arrival at the destination. But what history shows is that the most friction occurs in the transitions leading up to and following these things. There is the separation, a breakdown, like paper being torn. And there is the integration of new people into an existing community, a community that could receive that change as an injection of vitality and energy and economic investment, or as a burden and a stressor.

In part, that outcome depends on who is displaced. As Carlos Martín, then a senior fellow at the Urban Institute, told an audience of planners who had gathered to discuss migration in 2020, it often takes time to know whether a place will welcome new settlers. Immediately after Hurricane Katrina, people who resettled in Texas and elsewhere were greeted with empathy. A year later, though, talk of providing aid had shifted to questions about crime and competition for housing, code words for racial tensions. The sympathy turned to finger-pointing and anger. Sometimes it depends on who it is that’s arriving. Are they white or Black? Are they buying glass-curtain-walled condos, perhaps fueling gentrification but also goosing an economic boom? Or are they unemployed refugees looking for housing in the low-income suburbs? The answers shouldn’t matter, Martín says, but they do.

This article has been adapted from the book On the Move: The Overheating Earth and the Uprooting of America by Abrahm Lustgarten.

​When you buy a book using a link on this page, we receive a commission. Thank you for supporting The Atlantic.

Global warming may be slowing Earth's spin and affecting how we keep time

Science Global warming may be slowing Earth's spin and affecting how we keep time

Melting polar ice caps are a sad sign of our times, but they may have given global timekeepers an unexpected reprieve, according to new research.

For decades, experts have been trying to reconcile the precise time, as set by atomic clocks, with the somewhat unreliable speed at which the Earth spins.

Since 1972, authorities have added 27 leap seconds to our time standard – UTC, or Co-ordinated Universal Time – to compensate for a slow-down in the Earth's spin caused largely by the pull of the Moon on the oceans known as "tidal friction".

Keeping UTC in step with the Earth's rotation means, among other things, that we can expect the Sun to come up at a particular time in the morning, and astronomers can easily work out when to point their telescopes at a particular part of the sky.

But the addition of leap seconds happens at irregular intervals, with just six months' notice, causing a headache for global technology systems – from power grids to financial markets, and from satellites to social media networks.

Recently however,  Earth's spin has sped up  suggesting we might need to remove a second from UTC, rather than add one to it.

This has caused widespread concern that computers might not cope well with this "negative leap second" and there could be unprecedented disruption to global systems.

But what if this dreaded negative leap second was postponed – even for just a few years?

A new study, published in the journal Nature , suggests we may well get such a delay from the melting of Earth's ice caps, which are having a slowing effect on the planet's rotation.

Melting ice putting the brakes on Earth's spin

Duncan Agnew, a professor of geophysics at the University of California, San Diego, set out to model all the factors impacting the speed of Earth's rotation.

Some factors cause the Earth to spin faster, others cause it to slow down, and their net effect should explain the speed the planet spins at.

"It's almost a book-keeping exercise," Professor Agnew said.

His work adds weight to the idea the recent speeding up of Earth's rotation is due to changes in the Earth's liquid core. 

On the other hand, apart from tidal friction, he found another factor slowing the Earth's spin was the increased rate of polar melting, mostly from the Greenland ice cap but also from Antarctica.

"That was the most interesting result," he said.

"Global warming is … changing the rotation of the whole Earth."

So how does that work?

As polar ice melts, more water flows towards the equator and the impact can be likened to a figure skater who stretches out their arms and legs to slow down.

The slowing is due to a property of spinning systems called conservation of angular momentum.

"Because the shape of the Earth is changing, that causes the rotation to vary," Professor Agnew said.

He found the Earth was spinning ahead of the atomic clock and this would eventually require a leap second to be removed from UTC, in order to keep the two with a second of each other.

But Professor Agnew also found the impact of the Earth's melting polar ice has postponed the need for this negative leap second by three years.

According to his modelling, a second will need to be removed from UTC in 2029, rather than 2026.

"If global warming hadn't occurred over the last 30 years, we'd be very close to a negative leap second already."

The spectre of the negative leap second

The practice of adjusting UTC with leap seconds was put in place in a time before the internet.

In the '70s, it was important UTC matched the period of the Earth's rotation for purposes of celestial navigation, Patrizia Tavella, who is in charge of UTC at France's Bureau International des Poids et Measures (BIPM), said.

But since the advent of GPS and precise technologies that rely on atomic time, adjusting UTC has become a greater headache.

Adding leap seconds has led to computer glitches with widespread effects, including outages on social media site Reddit and Qantas servers in 2012, and web services company Cloudflare in 2017.

There's also little standardisation around how organisations adjust to UTC changes, with companies like Meta and Google taking different approaches.

"All that creates a great confusion on what time it is on the day of the leap seconds," Dr Tavella said.

Subtracting a second could cause unprecedented problems.

"A negative leap second has never been implemented.

"There are systems which have not been designed for this case, and the risk of failure is surely a concern for all the users and the metrologists."

Dr Tavella welcomed Professor Agnew's findings   that climate change has delayed the need for a negative leap second.

"If confirmed, it can be good news, as we have more time to study and take a sound decision on the future of the UTC." 

Michael Wouters from Australia's National Measurement Institute shared Dr Tavella's concerns.

But he emphasised the lack of certainty in predicting the required timing for negative leap seconds – which is why actual decisions about leap seconds are only made six months out.

"[Professor Agnew] really only looks at the effect of the polar melting on the timing of a leap second … and does not consider uncertainties in the other processes that affect Earth rotation," Dr Wouters said.

But he agreed with the key finding that polar melting may give some reprieve on the requirement for addition of a negative leap second. 

Studies shows reach of of global warming impact

Professor Agnew said his model involved the "simplest possible" extrapolation and acknowledged there was a "fairly large" amount of error, due mainly to the activity of the Earth's core being "fundamentally unpredictable".

Despite all this, an Australian expert in the study of the Earth's changing shape and rotation described the work as "robust" and "elegant" in its key finding.

"Enough ice is melting to change Earth's rotation rate and so our length of day," Matt King, a professor of polar geodesy at the University of Tasmania, said.

"We know [melting ice] also changes the location of the axis upon which Earth spins.

"These are profound things are happening outside the sight of most of us, but that doesn't mean they are trivial."

What happens next?

International time-keeping authorities are in the process of moving away from binding UTC so tightly to the rotation of the Earth.

By 2035 they hope to have a new system that requires fewer adjustments to UTC, but that will have no noticeable effects on our experience of daily things like sunrise and sunset times.

But what happens in the meantime?

Professor Agnew said the overall trend would be for Earth's rotation to slow, and the need for negative leap seconds in the long-term was "unlikely".

He said authorities should forget about introducing them and simply allow UTC and the speed of the Earth's rotation to diverge more before making adjustments.

And what if we gave up entirely on linking atomic clock time with the Earth's rotation?

Ultimately, it could result in some pretty strange phenomena.

Fancy a midday sunrise anyone?

• X (formerly Twitter)

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Science News

Climate change is changing how we keep time.

Melting ice sheets are slowing Earth's rotation speed, complicating global timekeeping

The rapidly accelerating melting of Earth’s polar ice sheets — including ice atop Greenland (shown here) — is slowing the planet’s spin, which affects global timekeeping.

EREM YUCEL/AFP via Getty Images

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By Carolyn Gramling

March 27, 2024 at 1:34 pm

Climate change may be making it harder to know exactly what time it is.

The rapid melting of the ice sheets atop Greenland and Antarctica, as measured by satellite-based gravitational measurements, is shifting more mass toward Earth’s waistline. And that extra bulge is slowing the planet’s rotation , geophysicist Duncan Agnew reports online March 27 in Nature . That climate change–driven mass shift is throwing a new wrench into international timekeeping standards.

The internationally agreed-upon coordinated universal time, or UTC, is set by atomic clocks, but that time is regularly adjusted to match Earth’s actual spin. Earth’s rotation isn’t always smooth sailing — the speed of the planet’s spin changes depending on a variety of factors, including gravitational drag from the sun and the moon, changes to the rotation speed of Earth’s core, friction between ocean waters and the seafloor, and shifts in the planet’s distribution of mass around its surface. Even earthquakes can affect the spin: The magnitude 9.1 earthquake in Indonesia in 2004, for example, altered the land surface in such a way that it caused Earth to rotate a tiny bit faster, says Agnew, of the Scripps Institution of Oceanography in La Jolla, Calif.

But the impact of that quake is much smaller than that of the ice sheets’ melting — a point that Agnew says he finds particularly startling. Humankind “has done something that affects, measurably, the rotation rate of the entire Earth.”

The need for occasional tweaks to the synchronization of atomic clocks and Earth’s rotation gave birth in 1972 to the “leap second ,” an extra tick that international timekeepers agreed to add to UTC as needed ( SN: 1/19/24 ). Timekeepers have added 27 leap seconds to the clock since the idea was introduced.

Still, metrologists — measurement scientists — aren’t overly fond of this system. For one thing, it doesn’t happen on a regular schedule, but only whenever it seems to be needed. And financial markets and satellite navigation systems, which rely on precise timing, each have their own methodologies for incorporating a leap second. Those inconsistencies can, counterproductively, make it more challenging to have a universal time. So in 2022, an international consortium of metrologists voted to do away with leap seconds in favor of adding larger chunks of time, perhaps a minute, less frequently. The group resolved to settle those details at its next meeting, in 2026.

That may not come a second too soon. The slightly slower rotation has actually delayed the need for timekeeping adjustments by a few years, Agnew says — in fact, as a result of this change, the last time a leap second was required to be inserted was in 2016. At the moment, in fact, Earth’s rotation and atomic clocks are nearly in sync.

But that’s just a brief respite, Agnew’s calculations show. The biggest changes to Earth’s rotation right now are coming from its heart: slowing rotation of Earth’s core is actually speeding up the spin of the outer layers ( SN: 1/23/23 ). That slowdown will ultimately mean that timekeepers, under the current system, must begin removing leap seconds from the UTC, rather than inserting them, to keep things in sync.

That shift in strategy might have begun as soon as in 2026. But the study suggests that, thanks to climate change, global timekeepers now have an extra two or three years before they need to adjust, notes geophysicist Jerry Mitrovica of Harvard University. But no realistic projections of future melting can forestall the inevitable beyond 2030, Mitrovica adds: One way or another, the world is going to have to start losing time — or international timekeeping guidelines will need to change.

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