article on global warming 2021

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2021 Continued Earth’s Warming Trend

Earth’s global average surface temperature in 2021 tied 2018 as the sixth-warmest year on record, according to independent analyses from NASA and the National Oceanic and Atmospheric Administration (NOAA).

Global temperatures in 2021 were 0.85 degrees Celsius (1.5 degrees Fahrenheit) above the average for NASA’s baseline period, according to scientists at NASA’s Goddard Institute for Space Studies (GISS). NASA uses the period from 1951-1980 as a baseline to compare how global temperatures change over time.

Collectively, the past eight years have been the warmest since modern recordkeeping began in 1880. This annual temperature data is part of the global temperature record that tells scientists how much and where our planet has been warming. Earth in 2021 was about 1.1°C (1.9°F) warmer than it was in the late 19th century, when the Industrial Revolution was underway and weather stations were popping up around the world.

The map above depicts global temperature anomalies in 2021. It does not show absolute temperatures; instead, it shows how much warmer or cooler each region of Earth was compared to the average from 1951 to 1980. The bar chart below shows 2021 in the context of the past 140 years. The values represent surface temperatures averaged over the entire globe for the year.

1880 - 2021

The long-term global warming trend is largely due to human activities that have increased emissions of carbon dioxide and other greenhouse gases into the atmosphere. The planet is already seeing the effects of global warming: Arctic sea ice is declining, sea levels are rising, and wildfires are becoming more severe. Understanding how the planet is changing—and how rapidly those changes are occurring—is crucial for preparing humanity to adapt to a warmer future.

NASA’s temperature analyses incorporate surface temperature measurements from more than 20,000 weather stations, ship- and buoy-based observations of sea surface temperatures, and temperature measurements from Antarctic research stations. These in situ , ground-based measurements are validated with satellite data from the Atmospheric Infrared Sounder (AIRS) on NASA’s Aqua satellite. The data are also analyzed using an algorithm that considers the varied spacing of temperature stations around the globe and urban heat island effects. The full dataset of global surface temperatures for 2021, as well as details of how NASA scientists conducted the analysis, are publicly available from GISS.

A separate, independent analysis by NOAA also concluded that the global surface temperature for 2021 was the sixth highest on record. NOAA scientists use much of the same raw temperature data in their analysis, but they have a different baseline period (1901-2000) and methodology.

“The complexity of the various analyses does not matter because the signals are so strong,” said Gavin Schmidt, director of GISS, NASA’s leading center for climate modeling and climate change research. “The trends are all the same because the trends are so large.”

Many factors affect the average temperature in any given year, including La Niña and El Niño climate patterns in the tropical Pacific. 2021 was a La Niña year, and NASA scientists estimate that those ocean conditions may have cooled global temperatures by about 0.03°C (0.06°F) from what the average might have been.

“Science leaves no room for doubt: Climate change is the existential threat of our time,” said NASA Administrator Bill Nelson. “Eight of the top 10 warmest years on our planet occurred in the last decade, an indisputable fact that underscores the need for bold action to safeguard the future of our country and all of humanity.”

NASA Earth Observatory images by Joshua Stevens , based on data from the NASA Goddard Institute for Space Studies . Story by Sofie Bates, NASA’s Earth Science News Team, with Michael Carlowicz .

The past eight years have been the warmest in the global record.

Image of the Day for January 14, 2022

Image of the Day Atmosphere Heat Land Water Human Presence Remote Sensing Temperature Extremes

View more Images of the Day:

Annual Global Temperature Records

Scientists at NASA report each year on the long-term trend of rising air temperatures over Earth’s land and sea surfaces. The team assembles its analysis with publicly available data from roughly 6,300 meteorological stations, ship and buoy-based observations, and Antarctic research stations.

References & Resources

• NASA (2022, January 13) Six Questions to Help You Understand the 6th Warmest Year on Record. Accessed January 13, 2022.
• NASA Goddard Institute for Space Studies (2022) GISS Surface Temperature Analysis (GISTEMP). Accessed January 13, 2022.
• NOAA National Centers for Environmental Information (2022, January 13) Assessing the Global Climate in 2021. Accessed January 13, 2022.
• NOAA (2022, January 13) 2021 was world’s 6th-warmest year on record. Accessed January 13, 2022.
• NASA Earth Observatory (2022) World of Change: Global Temperatures.
• NASA Earth Observatory (2018, October 19) The New UN Climate Report in One Sentence.
• NASA Earth Observatory (2015, January 21) Why So Many Global Temperature Records?
• NASA Earth Observatory (2010, June 3) Global Warming.

You might also be interested in    ( view all )

2017 was the second hottest year on record.

Globally averaged temperatures were 0.90 degrees Celsius (1.62 degrees Fahrenheit) warmer than the long-term mean.

Image of the Day Heat Human Presence Temperature Extremes

2020 Tied for Warmest Year on Record

Earth’s average temperature has risen more than 1.2°C (2°F) since the late 19th century.

Image of the Day Atmosphere Heat Remote Sensing Temperature Extremes

Global Temperature Record Broken for Third Consecutive Year

The planet’s average surface temperature has risen about 1.1°C (2.0°F) since the late 19th century.

Image of the Day Heat Temperature Extremes

2009 Ends Warmest Decade on Record

These maps illustrate just how much warmer temperatures were in 2009 and the decade (2000-2009) compared to average temperatures recorded between 1951 and 1980.

Image of the Day Atmosphere Heat

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State of the climate: How the world warmed in 2021

Zeke Hausfather

The climate data for 2021 is now mostly in, and it has proved to be another noteworthy year across the oceans, atmosphere, cryosphere and surface temperature of the planet.

In this article, Carbon Brief unpacks the different datasets, remarkable records and extreme events of last year. Use the links below to navigate between sections:

• Ocean heat content : It was the warmest year on record for ocean heat content, which increased markedly between 2020 and 2021.
• Surface temperature : It was between the fifth and seventh warmest year on record for surface temperature for the world as a whole, the fifth warmest for the world’s land regions, and the seventh warmest for the oceans.
• Warming over land : It was the warmest year on record in 25 countries, and in areas where 1.8 billion people live.
• Extreme weather : 2021 saw the warmest northern-hemisphere summer (June, July, and August) on record over the world’s land, along with extreme heatwaves, wildfires, and rainfall events.
• Comparison with climate model data : Observations fall well within the range of CMIP5 climate model projections over the past 70 years.
• Warming of the atmosphere : It was the sixth or eighth warmest year in the lower troposphere – the lower part of the atmosphere – depending on which dataset is used.
• Sea level rise : Sea levels reached new record-highs, with notable acceleration over the past three decades.
• Greenhouse gases : Concentrations reached record levels for CO2, methane and nitrous oxide.
• Sea ice extent : Arctic sea ice was well below the long-term average for most of the year, though relatively few daily records were set. The summer Arctic sea ice minimum was the 12th lowest since records began in the late 1970s.
• Looking ahead to 2022 : Carbon Brief predicts that global average temperature in 2022 will be similar to 2021. 

Record ocean heat content

Last year was the warmest on record for the heat content of the world’s oceans. Ocean heat content (OHC) has increased by around 417 zettajoules – a billion trillion joules – since the 1940s. The heat increase in 2021 alone compared to 2020 – about 14 zettajoules – is around 23 times more than the total energy used by everyone on Earth in 2019 (the latest year in which global primary energy statistics are available).

Human-emitted greenhouse gases trap extra heat in the atmosphere. While some of this warms the Earth’s surface, the vast majority – around of 93% – goes into the oceans. About two thirds of this accumulates in the top 700 metres, but some also ends up in the deep oceans. Annual OHC estimates between 1950 and present for both the upper 700m and 700m-2000m depths of the ocean are shown in the figure below.

In many ways, OHC represents a much better measure of climate change than global average surface temperatures. It is where most of the extra heat ends up and is much less variable on a year-to-year basis than surface temperatures.

Changes in the amount or rate of warming are much easier to detect in the OHC record than on the surface. For example, OHC shows little evidence of the modest slowdown in warming at the surface in the mid-2000s that got so much attention at the time. It also shows a distinct acceleration after 1991, matching the increased rate of greenhouse gas emissions over the past few decades.

Just about every year since 1991 has set a new OHC record, showing that heat has continued to accumulate in the Earth system as concentrations of atmospheric greenhouse gases have increased.

Fifth-to-seventh warmest year on the surface

Global surface temperatures in 2021 were among the warmest measured since records began in the mid-1800s. Data from NASA , NOAA and Berkeley Earth show it was the sixth warmest year on record, while data from Copernicus ERA5 has it as the fifth warmest. The release of the Hadley Centre/UEA HadCRUT5 record has been delayed due to data reporting problems, but it will likely show a similar ranking for 2021. 

In all cases, the records are effectively tied with 2015 and 2018, making 2021 anywhere between the fifth and seventh warmest on record within the bounds of measurement uncertainties. 

Global surface temperature records can be calculated back to 1850, though some groups choose to start their records in 1880 when more data was available. Prior to 1850, records exist for some specific regions, but are not sufficiently widespread to calculate global temperatures with any reasonable accuracy. These records are created by combining ship- and buoy-based measurements of ocean sea surface temperatures with temperature readings of the surface air temperature from weather stations on land (Copernicus ERA5 is an exception, as it uses weather model-based reanalysis ). 

The chart below shows global temperature records since 1850, with temperatures shown relative to the 1880-99 period to highlight warming since the pre-industrial period .

Temperatures in 2021 were between 1.1C and 1.2C warmer than temperatures in the late 19th century (between 1880 and 1900), depending on the temperature record chosen. Last year represented between the seventh and tenth consecutive year that global temperatures have exceeded 1C above pre-industrial levels across the different datasets.

The figure below shows surface temperatures since 1970, a period during which atmospheric greenhouse gas concentrations have been rapidly increasing. While 2021 is not quite as warm as the past two years, it is well in-line with the longer-term warming trend seen in the data.

The past seven years of the record really stand out as much warmer than anything that has come before. This can be seen in the figure below from Berkeley Earth. Each shaded curve represents the annual average temperature for that year. The further that curve is to the right, the warmer it was.

The width of each year’s curve reflects the uncertainty in the annual temperature values (caused by factors such as changes in measurement techniques and the fact that some parts of the world have fewer measurement locations than others).

Year-to-year variability in temperature records is mostly due to the influence of El Niño and La Niña events , which have a short-term warming or cooling impact on the climate. Other dips are associated with large volcanic eruptions . The longer-term warming of the climate is due to increases in atmospheric CO2 and other greenhouse gases emitted from human activity.

Last year’s temperatures were dragged down a bit by a modest La Niña event in the early part of the year, which reemerged in the last few months of the year (creating an uncommon “ double dip ” La Niña event). However, due to a lag of a few months between La Niña conditions in the Pacific and their peak effect on global temperatures, the La Niña conditions at the end of 2021 will likely result in a larger effect in 2022.

To assess the effects of El Niño and La Niña on the surface temperature record, Carbon Brief has produced an estimate of what temperatures would be in the absence of these events. The figure below shows estimated temperatures with El Niño removed (see the methods section at the end of the article for details on the approach used). The Copernicus record is not included in the figure as it does not have data available prior to 1979.

Removing the effects of El Niño and La Niña from the temperature record makes 2020 rather than 2016 the warmest year on record for all the temperature datasets, as 2016 temperatures benefited from a large El Niño event. It also generally reduces the difference between years over the 2015-21 period, though 2021 remains the sixth warmest year on record.

Temperatures for 2021 are bumped up modestly – by around 0.07C – with the cooling effects of the early-2021 La Niña event removed. Once El Niño effects are removed, the impact of major volcanic eruptions – such as those in 1982 and 1991 – are also much easier to spot in the temperature record.

Much more rapid warming over land

The focus on global surface temperature as a key metric of climate change is important, but can obscure very different rates of change across the planet.

For example, while most of the Earth’s surface is covered by oceans, nearly all human settlements and activities are in land areas. The land has been warming around 70% faster than the oceans – and 40% faster than the global average – in the years since 1970.

The figure below breaks down the Berkeley Earth temperature dataset into land-only (red) and ocean-only (blue) temperatures.

While the world as a whole has warmed by around 1.3C since the pre-industrial period (1850-1900) in the Berkeley Earth dataset, land areas have warmed a much larger amount – by 1.8C on average. In contrast, the oceans have warmed more slowly – by around 0.8C since pre-industrial times. (See Carbon Brief ’s guest post on why the land and ocean warm at different rates.)

Different parts of the land and ocean are also warming at different rates. The warmth in 2021 covered large regions of the world, with particularly anomalously high temperatures in northeast Canada, China, North and South Korea, the Middle East, and northern Africa. The figure below, from Berkeley Earth, shows the average annual temperatures, relative to 1951-80, across the world for the year.

A year of extremes

In addition to being one of the top-seven warmest years on record, 2021 saw many climate extremes around the world – including record-breaking extreme heat events , heavy rainfall and flooding , catastrophic wildfires , storms and drought .

Areas home to 1.8 billion people saw their warmest year on record during 2021, with 25 countries – including China, South Korea, Bangladesh and Nigeria – setting all-time annual temperature records. The figure below, also from Berkeley Earth, shows the regions of the world where either warm or cold records were set in 2021. 

It is noteworthy that while large parts of the planet set new warm records, there was no location on Earth where annual average temperatures were among the coldest on record.

China in particular saw exceptionally high temperatures in 2021, with annual average warmth exceeding 2C above pre-industrial levels for the first time. 

The northern-hemisphere summer months (June, July and August) were particularly warm, with the year seeing the hottest summer on record over the world’s land regions. The figure below shows summer temperatures from the Berkeley Earth dataset between 1850 and 2021. Each red dot represents the average temperature over the three months.  

A few extreme events in 2021 stand out as truly exceptional. In particular, a summer heatwave in northwestern North America in late June saw temperatures reach 49.6C (121F) in Canada, shattering the previous record of 45C (113F) set in 1937. The town in which this record was set was largely destroyed by a wildfire the following day.

An attribution study by the World Weather Attribution team found that the heatwave would have been “ virtually impossible ” without human-caused global warming. In a pre-industrial climate, the event would only be expected to occur once in every 150,000 years. Climate change to-date has made it 150 times more likely to occur, but it likely remains a relatively rare one-in-one-thousand year event, the scientists found.

However, in a scenario of 2C warming by the end of the century relative to pre-industrial (that is, 0.8C warming above current levels), such an extreme heatwave would “occur roughly every five to 10 years” in the region.

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The authors cautioned that there is a risk that even the 150 times more likely finding may underestimate the prevalence of these sorts of extremes in a warming world. They suggested that there is the possibility of “a non-linear threshold where a small amount of overall global warming is now causing a faster rise in extreme temperatures than has been observed so far”.

Last year also saw more than 50 hurricanes, cyclones and extratropical storms. There was deadly flooding in Nigeria, Ghana, India, Turkey, Germany, Belgium, the Netherlands and China, as well as, extreme heatwaves in Siberia, Pakistan, northern India, parts of the Middle East, North Africa and Europe, and catastrophic wildfires in the western US, the Mediterranean and ​​Israel.

The figure below, from a Carbon Brief guest post on summer extreme weather events, shows the location of different types of climate extremes experienced in 2021.

Observed temperatures close to climate model projections

Climate models provide physics-based estimates of future warming given different assumptions about future emissions, greenhouse gas concentrations and other climate-influencing factors .

Here, Carbon Brief examines a collection of climate models – known as CMIP5 – used in the 2013 fifth assessment report (AR5) from the Intergovernmental Panel on Climate Change (IPCC). In CMIP5, model estimates of temperatures prior to 2005 are a “hindcast” using known past climate influences, while temperatures projected after 2005 are a “forecast” based on an estimate of how things might change. 

The figure below shows the range of individual CMIP5 models projections since 1950, as well as future projections through to 2100 under the middle-of-the-road RCP4.5 emissions scenario. The black line shows the average of 38 different models, while the grey area shows the 95% ( two sigma ) range of the model projections. Observational temperatures are plotted on top of the climate model data, with individual observational records represented by coloured lines.

Observations fall well within the range of CMIP5 climate model projections over the past 70 years. Temperatures in 2021 are quite close to the model average. The climate model outputs shown here are blended – that is, they combine surface air temperature over the land with sea surface temperatures over the ocean in the same way they are measured in the observational climate record. This allows for a more accurate comparison of the two. 

The latest generation of models –  CMIP6 – are not compared to observations in this state of the climate report. The most recent report from the IPCC’s sixth assessment report (AR6) has changed the way that the ensemble of models is used. Rather than simply taking the average of all the models (and their range) – as was the case in previous IPCC reports – the IPCC decided to use a weighted subset of models that agreed well with historical observations. This also reflected a narrowing of climate sensitivity in the most recent IPCC report – such that a number of new models fall outside the “very likely” sensitivity range. 

While the IPCC AR6 provided a new set of future “assessed warming” projections, these start in the year 2015, which makes comparisons with observations over such a short period not very informative.

Warming of the atmosphere

In addition to surface measurements over the world’s land and oceans, satellite microwave sounding units have been providing estimates of temperatures at various layers of the atmosphere since 1979. 

The lowest layer they estimate – the lower troposphere – reflects temperatures a few kilometres above the surface and roughly corresponds to surface temperature changes. The record produced by Remote Sensing Systems (RSS) shows 2021 as the sixth warmest year on record in the lower troposphere, while the record from the University of Alabama, Huntsville (UAH) shows it as the eighth warmest. The chart below shows the two records – RSS in red and UAH in blue – for the lower troposphere (TLT).

The lower troposphere tends to be influenced more strongly by El Niño and La Niña events than the surface and satellite records show correspondingly larger warming or cooling spikes during these events. This is why, for example, 1998 shows up as one of the warmest years in satellites, but not in surface records.

The two lower tropospheric temperature records show large differences after the early 2000s. RSS shows an overall rate of warming quite similar to surface temperature records, while UAH shows considerably slower warming in recent years than has been observed on the surface. Both have seen large adjustments in recent years that have warmed RSS and cooled UAH compared to prior versions of each record.

In addition to a temperature record of the lower troposphere, RSS and UAH also provide measurements of the lower stratosphere – a region of the upper atmosphere around 18km above the surface. The lower stratosphere has been cooling for the last few decades in a clear fingerprint of human greenhouse gases, which warm the lower part of the atmosphere by trapping heat while cooling the upper atmosphere as less heat escapes. If other factors – such as changing solar output – were causing climate change, both the stratosphere and troposphere would be warming. 

The figure below shows lower stratospheric temperatures (TLS) records for both RSS (red) and UAH (blue) from 1979 through 2021.

Accelerating sea level rise

Modern-day sea levels have risen to a new high, due to a combination of melting land ice (such as glaciers and ice sheets), the thermal expansion of water as it warms, and changes in land water storage . In recent years, there have been larger contributions to sea level rise from melting ice sheets and glaciers, as warmer temperatures accelerate ice sheet losses in Greenland and Antarctica .

Since the early 1990s, the increase in global sea level has been estimated using altimeter data from satellites. Earlier global sea levels have been reconstructed from a network of global tide gauge measurements. This allows researchers to estimate how sea level has changed since the late 1800s . 

The chart below shows seven different sea level rise datasets (coloured lines), along with satellite altimeter measurements from NASA satellites as assessed by the University of Colorado (in black) after 1993. (As sea level rise data has not yet been released for the whole year, the 2021 value is estimated based on data through July.)

Sea levels have risen by around 0.2 metres (200mm) since 1900. While sea level rise estimates mostly agree in recent decades, larger divergences are evident before 1980. There is also evidence of accelerating sea level rise over the post-1993 period when high-quality satellite altimetry data is available. (See Carbon Brief’s explainer on how climate change is accelerating sea level rise.)

A portion of this sea level rise is being driven by melting land glaciers. Scientists measure the mass of glaciers around the world using a variety of remote sensing techniques, as well as through GRACE measurements of the Earth’s gravitational field. The balance between snow falling on a glacier and ice loss through melting and the breaking off – or “ calving ” – of icebergs determines if glaciers grow or shrink over time.

An international consortium called the World Glacier Monitoring Service tracks 164 different glaciers in 19 different regions around the world. The figure below shows the change in global average glacier mass from 1950 through to the end of 2020 (2021 values are not yet available). Note that glacier melt is reported in metres of water equivalent , which is a measure of how much mass has been lost on average.

Atmospheric greenhouse gases concentrations reach new highs

Greenhouse gas concentrations reached a new high in 2021, driven by human emissions from fossil fuels, land use and agriculture.

Three greenhouse gases – CO2, methane (CH4) and nitrous oxide (N2O) – are responsible for the bulk of additional heat trapped by human activities. CO2 is by far the largest factor, accounting for roughly 50% of the increase in “ radiative forcing ” since the year 1750. 

Methane accounts for 29%, while nitrous oxide accounts for around 5%. The remaining 16% comes from other factors including carbon monoxide, black carbon and halocarbons , such as CFCs.

Human emissions of greenhouse gases have increased atmospheric concentrations of CO2, methane and nitrous oxide to their highest levels in at least a few million years – if not longer. 

The figure below shows concentrations of these greenhouse gases – in parts per million (ppm) for CO2 (blue line) and parts per billion (ppb) for methane (orange) and nitrous oxide (red) – from the early 1980s through to October 2021 for CO2 and September 2021 for CH4 and N2O (the most recent data currently available).

Methane concentrations in particular have seen a sharp rise over the past decade after a plateau in the 2000s. This appears to be driven by both increased emissions from agriculture and fossil fuels, in roughly equal measure. To date there is limited evidence of methane from permafrost thaw meaningfully contributing to atmospheric concentrations according to the 2020 Global Methane Budget , though this may become a larger source in the future.  

Twelfth lowest Arctic sea ice on record

Arctic sea ice was at the low end of the historical (1979-2010) range for most of 2021, but saw few new all-time daily low records set outside of brief periods in February and July. The summer minimum extent – the lowest recorded level for the year – was the 12th lowest since records began in the late 1970s.

Antarctic sea ice was normal for the first half of the year, but fell to the low end of the historical range after October. (For more on how Antarctic sea ice extent has changed over recent decades, see the guest post that Carbon Brief published last year.)

The figure below shows both Arctic (red line) and Antarctic (blue line) sea ice extent for each day of the year, along with how it compares to the historical range (corresponding shading).

Looking ahead to 2022

With a “double dip” La Niña event in the latter part of 2021, La Niña conditions are expected to persist for at least the first three months of 2022. Because there is a lag of a few months between when El Niño or La Niña conditions peak in the tropical Pacific and their impact on global temperatures, these La Niña conditions will likely have a cooling influence on 2022 temperatures. 

So far, there are already three predictions – from the UK Met Office , NASA’s Dr Gavin Schmidt and Berkeley Earth – of what temperatures might look like in 2022.

For the first time, Carbon Brief provides its own prediction of likely 2022 temperatures – based on a model using the prior year (2021), temperatures over past three months, the El Niño/La Niño conditions over the past six months, and projections of El Niño/La Niño conditions over the next six months.

There are notable differences between four predictions of likely 2022 temperatures. The Met Office and the new Carbon Brief estimate have 2022 quite similar to 2021, with it very unlikely to be among the top 2 warmest years on record. Berkeley Earth predicts that 2022 will be a bit warmer, similar to 2017 which is the fourth warmest year on record, while Schmidt predicts that 2022 might end up tieing with 2016 and 2020 as the warmest year on record.

The figure below shows the four different 2022 predictions compared to the NASA GISTEMP temperature record. These have been “normalised” to show 2022 warming relative to the 2001-20 period in the NASA dataset. This is to remove any differences in predictions due to divergences between datasets in earlier parts of the temperature record.

While it is too early to predict with any certainty where 2022 will end up, it would be nothing out of the ordinary to have a year either similar to 2021 or 2020. 

What matters for the climate is not the leaderboard of individual years. Rather, it is the long-term upward trend in global temperatures driven by human emissions of greenhouse gases . Until the world reduces emissions down to net-zero, the planet will continue to warm .

• State of the Climate: How the world warmed in 2021

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The climate disaster is here

Earth is already becoming unlivable. Will governments act to stop this disaster from getting worse?

by Oliver Milman , Andrew Witherspoon , Rita Liu , and Alvin Chang

Thu 14 Oct 2021 05.00 EDT

The enormous, unprecedented pain and turmoil caused by the climate crisis is often discussed alongside what can seem like surprisingly small temperature increases – 1.5C or 2C hotter than it was in the era just before the car replaced the horse and cart. 

These temperature thresholds will again be the focus of upcoming UN climate talks at the COP26 summit in Scotland as countries variously dawdle or scramble to avert climate catastrophe. But the single digit numbers obscure huge ramifications at stake. “We have built a civilization based on a world that doesn’t exist anymore,” as Katharine Hayhoe, a climate scientist at Texas Tech University and chief scientist at the Nature Conservancy, puts it.

The world has already heated up by around 1.2C, on average, since the preindustrial era, pushing humanity beyond almost all historical boundaries. Cranking up the temperature of the entire globe this much within little more than a century is, in fact, extraordinary, with the oceans alone absorbing the heat equivalent of five Hiroshima atomic bombs dropping into the water every second.

When global temperatures are projected to hit key benchmarksthis century

Average global surface temperature relative to a 1850-1900 baseline.

Worst-case scenario

An unlikely pathway where emissions

are not mitigated

Intermediate

A pathway where emissions start declining

around 2040

An unlikely pathway where emissions start

declining now and global temperatures

peak at +1.8C

to increase

to 31 years

In 43 years

at the earliest

An unlikely pathway where emissions are not mitigated

A pathway where emissions start declining around 2040

An unlikely pathway where emissions start declining now

and global temperatures peak at +1.8C

An unlikely pathway where emissions start declining now and

global temperatures peak at +1.8C

An unlikely pathway

where emissions

A pathway where

emissions start

declining around 2040

An unlikely pathway where

emissions start declining now and

Guardian graphic. Source: IPCC, 2021: Summary for Policymakers. Note: The IPCC scenarios used for best-case, intermediate and worst-case scenarios are SSP1-2.6, SSP2-4.5 and SSP5-8.5.

Until now, human civilization has operated within a narrow, stable band of temperature. Through the burning of fossil fuels, we have now unmoored ourselves from our past, as if we have transplanted ourselves onto another planet. The last time it was hotter than now was at least 125,000 years ago, while the atmosphere has more heat-trapping carbon dioxide in it than any time in the past two million years, perhaps more.

Since 1970, the Earth’s temperature has raced upwards faster than in any comparable period. The oceans have heated up at a rate not seen in at least 11,000 years. “We are conducting an unprecedented experiment with our planet,” said Hayhoe. “The temperature has only moved a few tenths of a degree for us until now, just small wiggles in the road. But now we are hitting a curve we’ve never seen before.”

No one is entirely sure how this horrifying experiment will end but humans like defined goals and so, in the 2015 Paris climate agreement , nearly 200 countries agreed to limit the global temperature rise to “well below” 2C, with an aspirational goal to keep it to 1.5C. The latter target was fought for by smaller, poorer nations, aware that an existential threat of unlivable heatwaves, floods and drought hinged upon this ostensibly small increment. “The difference between 1.5C and 2C is a death sentence for the Maldives,” said Ibrahim Mohamed Solih, president of the country, to world leaders at the United Nations in September.

There is no huge chasm after a 1.49C rise, we are tumbling down a painful, worsening rocky slope rather than about to suddenly hit a sheer cliff edge – but by most standards the world’s governments are currently failing to avert a grim fate. “We are on a catastrophic path,” said António Guterres, secretary general of the UN. “We can either save our world or condemn humanity to a hellish future.”

Earth’s atmosphere, now saturated with emissions from human activity, is trapping warmth and leading to more frequent periods of extreme heat

• Oregon, US June 2021: A cooling shelter
• Yokohama, Japan July 2021: Staff sprinkles water to cool down patrons
• Seville, Spain August 2021: A billboard shows 47C (117F)
• Karachi, Pakistan September 2021: A zookeeper bathes an elephant

Photographs: Clockwise from top-left, Maranie Staab/Reuters, Yuichi Yamazaki/Getty Images, Rizwan Tabassum/AFP via Getty Images, Cristina Quicler/AFP via Getty Images

This year has provided bitter evidence that even current levels of warming are disastrous, with astounding floods in Germany and China , Hades-like fires from Canada to California to Greece and rain, rather than snow, falling for the first time at the summit of a rapidly melting Greenland. “No amount of global warming can be considered safe and people are already dying from climate change,” said Amanda Maycock, an expert in climate dynamics at the University of Leeds.

A “heat dome” that pulverized previous temperature records in the US’s Pacific northwest and Canada's west coast in June, killing hundreds of people as well as a billion sea creatures roasted alive in their shells off the coast , would’ve been “virtually impossible” if human activity hadn’t heated the planet, scientists have calculated, while the German floods were made nine times more likely by the climate crisis. “The fingerprint of climate change on recent extreme weather is quite clear,” said Michael Wehner, who specializes in climate attribution at Lawrence Berkeley National Laboratory. “But even I am surprised by the number and scale of weather disasters in 2021.”

Frequency and intensity of once-a-decade heatwave events

Increase in

temperature

A once-a-decade event ...

... now happens

2.8x a decade

In 6-11 years

About 30 years

Unlikely this

... now happens 2.8x a decade

Guardian graphic. Source: IPCC, 2021: Summary for Policymakers. Note: The projected year ranges for +1.5C scenario is using the mean projections for SSPI2.6 and SSP5-8.5. The +2C and +4C scenarios use the mean projection for SSP2-4.5.

After a Covid-induced blip last year, greenhouse gas emissions have roared back in 2021, further dampening slim hopes that the world will keep within the 1.5C limit. “There’s a high chance we will get to 1.5C in the next decade,” said Joeri Rogelj, a climate scientist at Imperial College London.

For humans, a comfortably livable planet starts to spiral away the more it heats up. At 1.5C, about 14% of the world’s population will be hit by severe heatwaves once every five years . with this number jumping to more than a third of the global population at 2C. 

Beyond 1.5C, the heat in tropical regions of the world will push societies to the limits , with stifling humidity preventing sweat from evaporating and making it difficult for people to cool down. Extreme heatwaves could make parts of the Middle East too hot for humans to endure, scientists have found, with rising temperatures also posing enormous risks for China and India .

A severe heatwave historically expected once a decade will happen every other year at 2C . “Something our great-grandparents maybe experienced once a lifetime will become a regular event,” said Rogelj. Globally, an extra 4.9 million people will die each year from extreme heat should the average temperature race beyond this point, scientists have estimated . 

At 2C warming , 99% of the world’s coral reefs also start to dissolve away, essentially ending warm-water corals. Nearly one in 10 vertebrate animals and almost one in five plants will lose half of their habitat. Ecosystems spanning corals, wetlands, alpine areas and the Arctic “are set to die off” at this level of heating, according to Rogelj.

Change in fraction of land annually exposed to heatwaves: Selected continent Globally Africa Asia Europe North America Oceania South America

With our current policies

Around 2030s

Change from 1986-2006

Guardian graphic. Source: Climate Impact Explorer by Climate Analytics. Note: In the data, a heatwave is when a relative indicator based on air temperature and an absolute indicator based on the air temperature and relative humidity are projected to exceed exceptionally high values, according to an analysis of four climate models. When the two of the four models don’t agree, they are not visualized. The projected year ranges are the Climate Action Tracker current policies scenario.

Earth’s hotter climate is causing the atmosphere to hold more water, then releasing the water in the form of extreme precipitation events

• Kolkata, India September 2021: A woman exits a bus onto a flooded street
• Agen, France September 2021: Firefighters inspect a flooded street
• Al Khaburah, Oman October 2021: Flooded streets after Cyclone Shaheen
• Ayutthaya, Thailand October 2021: A boy walks through floodwaters

Photographs: Clockwise from top-left, Indranil Aditya/NurPhoto via Getty Images, Philippe Lopez/AFP via Getty Images, Jack Taylor/AFP via Getty Images, Oman News Agency via AP

Across the planet, people are set to be strafed by cascading storms, heatwaves, flooding and drought. Around 216 million people, mostly from developing countries, will be forced to flee these impacts by 2050 unless radical action is taken, the World Bank has estimated . As much as $23tn is on track to be wiped from the global economy , potentially upending many more.

Some of the most dire impacts revolve around water – both the lack of it and inundation by it. Enormous floods, often fueled by abnormally heavy rainfall, have become a regular occurrence recently, not only in Germany and China but also from the US, where the Mississippi River spent most of 2019 in a state of flood, to the UK, which was hit by floods in 2020 after storms delivered the equivalent of one month of rain in 48 hours, to Sudan, where flooding wiped out more than 110,000 homes last year.

Frequency and intensity of once-a-decade heavy precipitation events

precipitation

1.3x a decade

Heavy precipitation

... now happens 1.3x a decade

Meanwhile, in the past 20 years the aggregated level of terrestrial water available to humanity has dropped at a rate of 1cm per year, with more than five billion people expected to have an inadequate water supply within the next three decades .

At 3C of warming, sea level rise from melting glaciers and ocean heat will also provide torrents of unwelcome water to coastal cities, with places such as Miami, Shanghai and Bangladesh in danger of becoming largely marine environments. The frequency of heavy precipitation events, the sort that soaked Germany and China, will start to climb, nearly doubling the historical norm once it heats up by 2C.

Change in the mass of precipitation: Selected continent Globally Africa Asia Europe North America Oceania South America

Guardian graphic. Source: Climate Impact Explorer by Climate Analytics. Note: The data shows where rainfall and snowfall are projected to change compared to the 1986-2006 average, according to an analysis of four climate models. When the two of the four models don’t agree, they are not visualized. The projected year ranges are the Climate Action Tracker current policies scenario.

Earth’s hotter atmosphere soaks up water from the earth, drying out trees and tinder that amplify the severity of wildfires

• Wooroloo, Australia February 2021: A wildfire destroyed over 30 homes
• Ogan Ilir, Indonesia August 2021: Indonesian firefighters try to extiguish a peatland fire
• Chefchaouen, Morocco August 2021: A woman looks at wildfires tearing through a forest
• California, US September 2021: Flames consume a house in the Fawn Fire

Photographs: Clockwise from top-left, Greg Bell/DFES via AP, Muhammad A.F/Anadolu Agency via Getty Images, Ethan Swope/AP, Fadel Senna/AFP via Getty Images

Virtually all of North America and Europe will be at heightened risk of wildfires at 3C of heating, with places like California already stuck in a debilitating cycle of “heat, drought and fire”, according to scientists. The magnitude of the disastrous “Black Summer” bushfire season in Australia in 2019-20 will be four times more likely to reoccur at 2C of heating , and will be fairly commonplace at 3C. 

A disquieting unknown for climate scientists is the knock-on impacts as epochal norms continue to fall. Record wildfires in California last year, for example, resulted in a million children missing a significant amount of time in school. What if permafrost melting or flooding cuts off critical roads used by supply chains? What if storms knock out the world’s leading computer chip factory? What happens once half of the world is exposed to disease-carrying mosquitos? 

“We’ve never seen the climate change this fast so we don’t understand the non-linear effects,” said Hayhoe. “There are tipping points in our human-built systems that we don’t think about enough. More carbon means worse impacts which means more unpleasant surprises.”

Change in fraction of land annually exposed to wildfires: Selected continent Globally Africa Asia Europe North America Oceania South America

Guardian graphic. Source: Climate Impact Explorer by Climate Analytics. Note: The data shows where the annual aggregated of areas burned by wildfires is projected to change, according to an analysis of four climate models. When the two of the four models don’t agree, they are not visualized. The projected year ranges are the Climate Action Tracker current policies scenario.

Crop failure

Unpredictable weather, like too much or too little rainfall, decreases the quantity and quality of crop yields

• La Ceiba Talquezal, Guatemala May 2017: Crops on a hillside damaged by deforestation, pests and prolonged droughts
• New South Wales, Australia October 2019: A farmer stands in a paddock of failed wheat crop
• Lusaka, Zambia January 2020: Poor crops after the lack of normal summer rainfall
• Badghis, Afghanistan September 2021: A farmer holds a handful of failed wheat from his crop

Photographs: Clockwise from top-left, Marvin Recinos/AFP via Getty Images, David Gray/Getty Images, String/EPA, World Food Program/Reuters

There are few less pleasant impacts in life than famine and the climate crisis is beginning to take a toll on food production. In August, the UN said that Madagascar was on the brink of the world’s first “climate change famine”, with tens of thousands of people at risk following four years with barely any rain. Globally, extreme crop drought events that previously occurred once a decade on average will more than double in their frequency at 2C of temperature rise. 

Heat the world a bit more than this and a third of all the world’s food production will be at risk by the end of the century as crops start to wilt and fail in the heat.

Frequency of once-a-decade crop drought events

Crop drought

... now happens 1.7x a decade

In 6-8 years

Many different aspects of the climate crisis will destabilize food production, such as dropping levels of groundwater and shrinking snowpacks, another critical source of irrigation, in places such as the Himalayas. Crop yields decline the hotter it gets, while more extreme floods and storms risk ruining vast tracts of farmland.

Change in fraction of land annually exposed to crop failure: Selected continent Globally Africa Asia Europe North America Oceania South America

Guardian graphic. Source: Climate Impact Explorer by Climate Analytics. Note: The data shows where the annual yield of four crops (maize, wheat, soybean, and rice) is projected to fall short of the 2.5th percentile of pre-industrial levels, according to an analysis of four climate models. When the two of the four models don’t agree, they are not visualized. The projected year ranges are the Climate Action Tracker current policies scenario.

Despite the rapid advance of renewable energy and, more recently, electric vehicles, countries still remain umbilically connected to fossil fuels, subsidizing oil, coal and gas to the tune of around $11m every single minute . The air pollution alone from burning these fuels kills nearly nine million people each year globally. Decades of time has been squandered – US president Lyndon Johnson was warned of the climate crisis by scientists when Joe Biden was still in college and yet industry denial and government inertia means the world is set for a 2.7C increase in temperature this century, even if all emissions reduction pledges are met.

By the end of this year the world will have burned through 86% of the carbon “budget” that would allow us just a coin flip’s chance of staying below 1.5C. The Glasgow COP talks will somehow have to bridge this yawning gap, with scientists warning the world will have to cut emissions in half this decade before zeroing them out by 2050.

“2.7C would be very bad,” said Wehner, who explained that extreme rainfall would be up to a quarter heavier than now, and heatwaves potentially 6C hotter in many countries. Maycock added that much of the planet will become “uninhabitable” at this level of heating. “We would not want to live in that world,” she said.

A scenario approaching some sort of apocalypse would comfortably arrive should the world heat up by 4C or more, and although this is considered unlikely due to the belated action by governments, it should provide little comfort. 

Every decision – every oil drilling lease, every acre of the Amazon rainforest torched for livestock pasture, every new gas-guzzling SUV that rolls onto the road – will decide how far we tumble down the hill. In Glasgow, governments will be challenged to show they will fight every fraction of temperature rise, or else, in the words of Greta Thunberg , this pivotal gathering is at risk of being dismissed as “blah, blah, blah”.

“We’ve run down the clock but it’s never too late,” said Rogelj. “1.7C is better than 1.9C which is better than 3C. Cutting emissions tomorrow is better than the day after, because we can always avoid worse happening. The action is far too slow at the moment, but we can still act.”

This article was amended on 15 October 2021 with the correct IPCC projections for when global temperatures are expected to reach each threshold and to correct the spelling of Wooroloo. The time ranges in each map have also been amended to show time range projections from the Climate Action Tracker's current policies pathway. It was further amended on 25 October 2021 to add the west coast of Canada to the areas affected by the "heat dome" in June.

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Forget ‘doomers.’ Warming can be stopped, top climate scientist says

Michael Mann points to prehistoric catastrophes, modern environmental victories

Alvin Powell

Harvard Staff Writer

Keeping the Earth’s warming below the 1.5-degree Celsius threshold that scientists believe will stave off climate change’s worst effects is a tall task, but one of the world’s top climate scientists believes climate “doomism” won’t help the fight. And Michael Mann is all about the fight.

“I push back on doomism because I don’t think it’s justified by the science, and I think it potentially leads us down a path of inaction,” said Mann during a talk last Thursday at the Harvard Kennedy School’s Belfer Center for Science and International Affairs . “And there are bad actors today who are fanning the flames of climate doomism because they understand that it takes those who are most likely to be on the front lines, advocating for change, and pushes them to the sidelines, which is where polluters and petrostates want them.”

“I push back on doomism because I don’t think it’s justified by the science, and I think it potentially leads us down a path of inaction.” Michael Mann

One recent victory for the University of Pennsylvania professor stems back to 2012, when climate change deniers and critics of his work wrote blog posts accusing him of scientific fraud. Mann demanded retractions. They refused, and he sued them for defamation. The case dragged on for years, but in February, Mann won $1,000 in punitive damages from one blogger and $1 million from the second.

Mann’s lecture, “ Can Lessons from Earth’s Past Help Us Survive Our Current Climate Crisis? ,” sought lessons from past climate change events in the Earth’s history, encompassing the demise of non-avian dinosaurs, the “Great Dying” 250 million years ago, pop musicians The Police — who sang of doomed dinosaurs — and famed astronomer Carl Sagan.

Mann, whose most recent book, “Our Fragile Moment,” was published in September, said the demise of the dinosaurs offers an example of the potentially deadly impact of climate change — in that case, from global cooling.

It is believed that a comet struck the Earth 65 million years ago, resulting in the death of non-avian dinosaurs. Most of them were not killed by the strike itself, but the drop in temperature caused by the rise of dust from the impact, which blocked the sun.

Small mammals, able to shelter in burrows, did survive, beginning an evolutionary process that would lead to humans. Sagan, the late scientist and science communicator, warned of a similar effect in the event of global nuclear war, which would likely bring on “nuclear winter” severe enough to bring on an extinction event.

Mann also discussed the “Great Dying,” which killed some 90 percent of species. It took place at a time when the Earth’s temperature spiked relatively suddenly in geologic terms. He said it was likely brought on by carbon dioxide being released in a major outbreak of volcanism that stretched thousands of years.

The current human-induced climate change has parallels to that time but is occurring much more rapidly, over tens of years rather than thousands.

“Warming today is hundreds of times faster than any warming in geological history,” Mann said, adding that the direction of the temperature swing — warmer or cooler — doesn’t matter. “Anything that takes you from the climate you’re adapted to is a threat.”

Mann’s work brought that point home back in 1999, when he and colleagues published a reconstruction of climate for the past 1,000 years. They used statistical methods they’d devised to combine climate proxies like ancient tree ring data, ice cores, and lake sediment into a single picture of the Earth’s climate history.

Represented graphically, the global mean temperature data resembled a hockey stick, with centuries of slowly declining temperatures making up the long handle and the sharp uptick in temperatures since the Industrial Revolution making up the blade. That “hockey stick” graph has since been hailed as evidence that the recent decades’ warming is neither natural nor a figment of scientists’ imagination.

During the event, Mann said the “Great Dying” era offers other lessons because it has been theorized that the warming was due to a major release of methane from the ocean, and some climate pessimists, whom he called “doomers,” believe a similar dynamic is already at work today, at least partly due to thawing of the arctic permafrost. In fact, he said they believe that enough methane has been released that it is already too late to avoid extinction-level warming.

Mann rebuts this view, noting it is inconsistent with the latest scientific understanding of the ancient event as well as evidence about today’s situation. And it serves as a distraction at a time when urgent action is needed.

Many have noted the already-existing anxiety about climate change inaction among today’s youth. Mann said in the interview during his campus visit that he would hope examples of the past will energize them rather than make them feel helpless.

Younger people today, he said, haven’t lived through high-profile environmental crises of the past, such as water pollution like that of Cleveland’s Cuyahoga River, once so full of industrial pollutants it periodically caught fire; power plant emissions, which created acid rain that damaged downwind forests and made lakes acidic; and the creation of a massive hole in the Earth’s protective ozone layer, which threatened to raise cancer rates around the Southern Hemisphere.

Each of those problems, while not on the scale of climate change, was analyzed by scientists and solved by policy: the Clean Water Act, the Clean Air Act, and the international Montreal Protocol.

Mann’s talk wassponsored by the Belfer Center’s Environment and Natural Resources Program and its Arctic Initiative ; the Shorenstein Center on Media, Politics and Public Policy ; the Salata Institute for Climate and Sustainability , and the HKS Climate, Energy, & Environment Professional Interest Council .

It was introduced by Henry Lee , director of the Environment and Natural Resources Program, and by Shorenstein Center senior fellow Cristine Russell , who engaged Mann in a question and answer session after his talk.

Mann noted that a difficult road lies ahead, but there is time still to limit warming to 1.5 degrees C. He cited as encouraging the U.S. passage of the Inflation Reduction Act — which contains significant provisions to fight climate change — and the global agreement in 2021’s COP 26, whose commitments, if enacted, would limit warming to 2 degrees C, which Mann acknowledged is still too high.

“It’s not too late for us to take the actions to keep warming below 1.5 Celsius. The obstacles at this point aren’t physical, they are not technological, they are entirely political,” he said. “And political obstacles can be overcome.”

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ENCYCLOPEDIC ENTRY

Global warming.

The causes, effects, and complexities of global warming are important to understand so that we can fight for the health of our planet.

Earth Science, Climatology

Tennessee Power Plant

Ash spews from a coal-fueled power plant in New Johnsonville, Tennessee, United States.

Photograph by Emory Kristof/ National Geographic

Global warming is the long-term warming of the planet’s overall temperature. Though this warming trend has been going on for a long time, its pace has significantly increased in the last hundred years due to the burning of fossil fuels . As the human population has increased, so has the volume of fossil fuels burned. Fossil fuels include coal, oil, and natural gas, and burning them causes what is known as the “greenhouse effect” in Earth’s atmosphere.

The greenhouse effect is when the sun’s rays penetrate the atmosphere, but when that heat is reflected off the surface cannot escape back into space. Gases produced by the burning of fossil fuels prevent the heat from leaving the atmosphere. These greenhouse gasses are carbon dioxide , chlorofluorocarbons, water vapor , methane , and nitrous oxide . The excess heat in the atmosphere has caused the average global temperature to rise overtime, otherwise known as global warming.

Global warming has presented another issue called climate change. Sometimes these phrases are used interchangeably, however, they are different. Climate change refers to changes in weather patterns and growing seasons around the world. It also refers to sea level rise caused by the expansion of warmer seas and melting ice sheets and glaciers . Global warming causes climate change, which poses a serious threat to life on Earth in the forms of widespread flooding and extreme weather. Scientists continue to study global warming and its impact on Earth.

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The unassuming material that could soak up carbon emissions

Researchers want to use the ultrafine rock particles left by eroding glaciers — called ‘rock flour’ — to suck climate-warming carbon from the air.

Minik Rosing grew up around the fine mud flowing from Greenland’s glaciers. It wasn’t until much later, when his own daughter had grown up and was in her mid-20s, that he realized how special it is.

During a family vacation in rural Greenland, where there was no electricity, she was fishing ice out of a milky-blue fjord for a gin and tonic when that mud gripped her feet so tightly that she had to abandon one of her boots.

As temperatures rise, meltwater is flushing out millions of tons of this stuff: ultrafine powder ground down by the island’s melting glaciers. Geologists have a culinary-sounding name for the microscopic particles: “rock flour.”

The loss of his daughter’s boot got Rosing thinking. Maybe those tiny grains of rock could be used to trap something much bigger: the carbon emissions that are altering the frozen landscape and way of life on the island.

“Greenland has been seen as the example and the horror story of climate change, and never been portrayed as a part of the solution,” said Rosing, a geology professor at the University of Copenhagen in Denmark who was born in Greenland.

As global emissions continue to rocket, he is part of a growing group of scientists looking for ways to suck carbon right out of the sky, an example of a sometime contentious suite of technologies called geoengineering.

For Rosing, the massive Arctic island’s exceptional mud represents not only a way of dialing back global warming but also an opportunity to change “the rest of the world’s impression of the Arctic” from ground zero for climate change to a solution for it.

Petrifying the air

Give it enough time and most of the carbon dioxide that humanity is pumping into the air will be taken back by the planet. CO2 dissolves in rainwater and reacts with rocks to form carbon-containing compounds that lock the gas out of the atmosphere. That naturally occurring process, called “chemical weathering,” literally petrifies the air.

The problem — at least for us humans — is that chemical weathering takes millennia to work its carbon-absorbing magic. Humanity doesn’t have that kind of time: The U.N. Intergovernmental Panel on Climate Change says society needs to drastically reduce CO2 emissions by the end of the decade. The situation has gotten so bad that the panel of scientists says we need to develop ways of pulling carbon from the air to avert catastrophe.

So what if we could speed things up? What if, Minik Rosing and other scientists wonder, we exposed more carbon-absorbing rocks to the carbon-laden air? They call that technique “enhanced weathering.”

Most enhanced-weathering proposals involve pulverizing tons of basalt or other rocks and spreading them across the land. But all that crushing would consume an enormous amount of energy that might result in more greenhouse-gas emissions.

That’s where rock flour comes in.

Glaciers flow over the bedrock like a slow-moving river. Over centuries, the tremendous weight of the ice grinds the rock underneath into a fine powder only a few ten-thousandths of a centimeter, or microns, in diameter — finer than most sand found on a beach.

During a Zoom interview, Rosing poured a bit of cream-colored rock flour from Greenland onto his index finger and held it up to the camera.

“If you see here on my finger now,” he said, “there’s absolutely no grains you can see.” Greenland’s ice sheets have already done the hard, dirty work of milling the rocks. Rubbing his fingers, he said it felt as soft as talc, an ingredient in many baby powders.

The fineness of the grains is the flour’s advantage. It gives the substance an enormous surface area to expose to the air, making it an attractive candidate for enhanced weathering. That high surface area is also what gripped the boots of Minik Rosing’s daughter, Johanne Aviaja Rosing, so thoroughly. “Every time I tried to pull one foot up,” she recalled, “the other foot just went down.”

“Other groups or companies are looking at using other types of rocks for enhanced rock weathering, but they have to crush the material,” said Christiana Dietzen, a soil scientist working with Rosing. “Even if they’re doing that, they’re kind of lucky to get to a hundred microns.”

The power of ‘rock flour’

To test how well rock flour stashes carbon, Rosing and Dietzen hauled about 200 tons of the stuff from Greenland for experiments.

The material packed a one-two punch, according to a pair of papers the researchers published last year: Not only did it suck up carbon when spread over farm fields in southern Denmark, but it also enriched the soil with nutrients and increased the yield of corn and potatoes in the first year of application.

The researchers estimate that, given enough time, spreading rock flour on all agricultural land in Denmark would suck up a quantity of carbon approximately equal to the annual emissions of that country (or of Hong Kong or Syria ). Preliminary results show longer-lasting crop yields in nutrient-poor soil in Ghana.

“There’s a novelty to the idea in using pre-ground material,” said Bob Hilton, an Oxford geochemist not involved in the research. “There’s interest in the idea because glacier processes produce huge amounts of this material.”

But there is still a lot of work to do before any farmer begins dusting their fields with rock flour.

So far, the studies have only measured the crop yield and carbon-absorbing effects over short periods of time. The rock flour works best in certain soil — slightly but not too acidic. Rosing and other enhanced-weathering researchers need to measure more precisely how much CO2 their techniques are taking up, so farmers and others can eventually make money by selling carbon credits.

“It is not easy to figure out how much CO2 has been sequestered in these field operations,” said Susan Brantley, a geochemist at Pennsylvania State University.

Even though no extra energy needs to go into crushing rock flour, it may come with other environmental costs, such as the greenhouse-gas pollution from shipping it across the ocean and impacts on local ecosystems. And even though Greenland’s frigid waters slow the weathering process, rock flour would have already reacted with some CO2.

“Just because these areas look like sediment factories, if you like, doesn’t mean that the grains haven’t already reacted in some way,” Hilton said.

Last year, Rosing helped found the Rock Flour Company . It has raised $2 million and plans to seek approval from the government of Greenland, an autonomous territory of Denmark, to mine and export rock flour. The process of assessing the environmental and social impacts will take years.

“We have quite high environmental standards regarding our mining sector,” said Naaja Nathanielsen, a minster overseeing minerals in Greenland. “It’s a long process, and it’s not a one size fits all.” But she added that she expects scooping rock flour from the shore would have a lower impact than hard-rock mining for nickel and other minerals that other firms are eyeing in Greenland.

“It’s a tension I think about a lot in that I would love to accelerate the process from a personal perspective in order to have climate impact,” said Clive Eley, a Rock Flour Company board member. “But at the same time, you don’t want to accelerate to the detriment of its full potential.”

Rosing hopes rock flour not only alters the trajectory of climate change, but changes the perception of his birthplace, too. He was born in a small settlement on Nuuk Fjord in West Greenland, not far from where he extracted his magic mud.

“Greenland is already seen as the parking lot of problems,” he said. “The Arctic is seen as a victim with no agency, and it would be really nice for Greenland to be relevant to the world in a positive way.”

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Interior Department rule aims to crack down on methane leaks from oil, gas drilling on public lands

FILE - Interior Secretary Deb Haaland announces that her agency will work to restore more large bison herds during a speech for World Wildlife Day at the National Geographic Society in Washington, Friday, March 3, 2023. The Biden administration issued a final rule Wednesday, March 27, 2024, aimed at curbing methane leaks from oil and gas drilling on federal and tribal lands, its latest action to crack down on emissions of methane, a potent greenhouse gas that contributes significantly to global warming. (AP Photo/Andrew Harnik, File)

FILE - A flare burns at a well pad Aug. 26, 2021, near Watford City, N.D. American oil and natural gas wells, pipelines and compressors are spewing three times the amount of the potent heat-trapping gas methane as the government thinks, a new comprehensive study calculates. (AP Photo/Matthew Brown, File)

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WASHINGTON (AP) — The Biden administration issued a final rule Wednesday aimed at curbing methane leaks from oil and gas drilling on federal and tribal lands, its latest action to crack down on emissions of methane, a potent greenhouse gas that contributes significantly to global warming.

The rule issued by the Interior Department’s Bureau of Land Management will tighten limits on gas flaring on federal lands and require that energy companies improve methods to detect methane leaks that add to planet-warming greenhouse gas pollution.

The action follows a more comprehensive methane-reduction plan announced by the Environmental Protection Agency in December. The plan, announced at a global climate conference in the United Arab Emirates, targets emissions from existing oil and gas wells nationwide, rather than focusing only on new wells, as previous EPA regulations have done. It also regulates smaller wells that are now required to find and plug methane leaks.

Oil and gas production is the nation’s largest industrial source of methane, the primary component of natural gas, and is a key target for Biden as his administration seeks to combat climate change. Methane is a climate “super pollutant” that is many times more potent in the short term than carbon dioxide.

The rule issued Wednesday updates regulations that are more than 40 years old and will hold oil and gas companies accountable by imposing stricter limits on flaring and requiring energy companies to find and fix leaks, administration officials said. At the same time, officials said they are moving to ensure that American taxpayers and tribal mineral owners are fairly compensated through higher royalty payments proposed last year.

The final rule will help “prevent waste, protect our environment and ensure a fair return to American taxpayers,” Interior Secretary Deb Haaland said in a statement.

“By leveraging modern technology and best practices to reduce natural gas waste, we are taking long-overdue steps that will increase accountability for oil and gas operators and benefit energy communities now and for generations to come,” she said.

The rule, which takes effect in June, is expected to generate more than $50 million per year in additional royalties while preventing billions of cubic feet of natural gas from being wasted through venting, flaring and leaks, Haaland and other officials said.

Venting and flaring activity from oil and gas production on public lands has significantly increased in recent decades. Between 2010 and 2020, total volumes of natural gas lost to venting and flaring on federal and tribal lands averaged about 44.2 billion cubic feet per year — enough to serve roughly 675,000 homes, the Interior said. The figure represents a sharp increase from an annual average of 11 billion cubic feet lost to venting and flaring in the 1990s.

Environmental groups hailed the rule, calling methane a huge contributor to global warming.

“Strong Interior Department methane waste rules are integral for the United States to protect taxpayers from wasted energy resources,” said Jon Goldstein, senior director of regulatory and legislative affairs at the Environmental Defense Fund.

“Eliminating waste from routine venting and flaring of associated gas conserves domestic energy resources ... lessens oil and gas production’s negative impact on the climate and protects the health of frontline communities,” said Tannis Fox, senior attorney at the Western Environmental Law Center, another environmental group.

The American Petroleum Institute, the top lobbying group for the oil and gas industry, called the new rule an overreach that could hamper U.S. energy production.

“API supports a smart regulatory framework for reducing methane emissions, but overlapping regulations and lack of coordination between policymakers could hinder progress, create unnecessary barriers to development on federal lands and result in regulatory incoherence,’' said Holly Hopkins, an API vice president.

Arizona Rep. Raul Grijalva, the top Democrat on the House Natural Resources Committee, called the rule a “much-needed step” to fight climate change and protect the health of communities near drilling sites throughout the West.

“Big Oil and Gas have been getting away with sloppy operations for too long, without an ounce of regard for the destruction it’s causing,’' Grijalva said. “I’m grateful the Biden administration is taking the bold action we need to hold fossil fuel facilities to a higher standard.’'

Interior had previously announced a rule to restrict methane emissions under former President Barack Obama. The plan was challenged in court and later weakened under former President Donald Trump. Competing court rulings blocked enforcement of the Trump and Obama-era rules, leading the agency to revert to rules developed more than 40 years ago.

Besides the EPA rule, a 2022 climate law approved by Congress is set to impose a fee on energy producers that exceed a certain level of methane emissions. The fee, initially set at $900 per metric ton of methane, will mark the first time the federal government has directly imposed a tax on greenhouse gas emissions.

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• Published: 04 April 2024

Climate chronicles

Global carbon emissions in 2023

• Zhu Liu   ORCID: orcid.org/0000-0002-8968-7050 1 , 2 , 3 ,
• Zhu Deng   ORCID: orcid.org/0000-0002-6409-9578 1 , 2 , 4 ,
• Steven J. Davis   ORCID: orcid.org/0000-0002-9338-0844 5 &
• Philippe Ciais   ORCID: orcid.org/0000-0001-8560-4943 6  

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Global CO 2 emissions for 2023 increased by only 0.1% relative to 2022 (following increases of 5.4% and 1.9% in 2021 and 2022, respectively), reaching 35.8 Gt CO 2 . These 2023 emissions consumed 10–66.7% of the remaining carbon budget to limit warming to 1.5°C, suggesting permissible emissions could be depleted within 0.5–6 years (67% likelihood).

Data from the Carbon Monitor indicate 35.8 Gt CO 2 were emitted globally in 2023.

Although the trend is upwards, the pace of growth has been slowing, suggesting global emissions might have plateaued.

India overtook the EU as the third highest emitter globally.

You have full access to this article via your institution.

Annual global CO 2 emissions dropped markedly in 2020 owing to the COVID-19 pandemic, decreasing by 5.8% relative to 2019 (ref. 1 ). There were hopes that green economic stimulus packages during the COVD crisis might mark the beginning of a longer-term decrease in global emissions toward net-zero emissions, but instead emissions rebounded and quickly exceeded pre-pandemic levels by 2021. However, year-on-year growth has slowed, with 5.4% increases in 2021 (ref. 2 ) (reaching 35.1 Gt CO 2 ) and 1.9% increases in 2022 (ref. 3 ) (reaching 35.7 Gt CO 2 ), rapidly using up the remaining carbon budget. Here, we outline global CO 2 emissions (encompassing fossil fuel combustion and cement production) from the Carbon Monitor project ( https://carbonmonitor.org ) for the year 2023.

Global CO 2 emissions in 2023

Overall, global CO 2 emissions in 2023 reached 35.8 ± 0.3 Gt CO 2 , an all-time high (Fig.  1 ). Total emissions were 35.3, 33.3, 35.1 and 35.7 in 2019–2022, meaning year-on-year changes of –5.8% from 2019 to 2020, 5.4% from 2020 to 2021, 1.9% from 2021 to 2022 and 0.1% from 2022 to 2023. This slight increase of 0.1% (–0.6 to + 1.1%) from 2022 to 2023 is less than the 1.1 ± 1.0% increase forecast by the Global Carbon Project (GCP) 4 . Although difficult to predict, the continued deceleration in growth rates might signal a plateauing or peaking of global CO 2 emissions in 2023, as has been suggested by the International Energy Agency (IEA) 5 . The trajectory of emissions in 2024 will offer further evidence.

Historical CO 2 emissions from fossil fuel combustion and the process of cement production (‘Fossil CO 2 ’) 8 coloured by industry sector, and those with land-use change (LUC) emissions 4 (‘Fossil + LUC’). International bunkers describe emissions from international aviation and international shipping. The inset displays daily near-real-time CO 2 emissions since 2019 from the Carbon Monitor 1 initiative and year-on-year percent changes. Note that total emissions and percent changes have been revised slightly from earlier estimates 2 , 3 owing to revised data and updated methodologies 9 , 10 . Global CO 2 emissions continued to grow after a brief decline in 2020, but the rate of that growth slowed in 2023; if these progressions continue, the remaining 1.5 °C carbon budget could be used within 0.5–6 years.

The sectoral contributions to these emissions are broadly similar to previous years. The power sector accounted for 38.4% of global CO 2 emissions, industry for 29.0%, ground transportation for 18.6%, residential for 9.4%, international bunkers (international aviation and shipping) for 3.5%, and domestic aviation for 1.0%. Moreover, the pattern of decelerating growth of 2023 global emissions is also evident at the sectoral level. For instance, year-on-year changes in power sector emissions went from + 0.9% in 2022 to –0.2% in 2023, industry emissions from + 1.6% to –0.8%, residential emissions from + 0.9% to –5.5%, and international bunkers from + 18.1% to + 8.9%. However, there were exceptions: ground transportation growth increased from + 2.5% in 2022 to + 3.1% in 2023, while domestic aviation rebounded from –1.0% in 2022 to + 14.0% in 2023. Nevertheless, both domestic and international aviation remain below pre-pandemic levels (2023 emissions were –1.9% and –9.6% less than 2019, respectively).

At the country level, combined emissions from the top five emitters remain similar to previous years. In descending order, China, the United States, India, the European Union (excluding the UK), and Russia collectively accounted for 64% of global emissions, or 23.0 Gt CO 2 . However, interannual fluctuations are apparent when comparing 2022 and 2023, making it difficult to predict long time trends toward zero emissions. For instance, emissions from China (the largest emitter) decreased by 1.9% to 11.0 Gt CO 2 in 2022 but rebounded + 2.9% to 11.3 Gt CO 2 in 2023. By contrast, other regions have maintained earlier increases. Emissions from India, for example, surged by 6.9% to 2.6 Gt CO 2 in 2022 and by another 4.4% to 2.8 Gt CO 2 in 2023; in doing so, India surpassed the EU to become the third highest emitter. Russia exhibited a similar increase, whereby emissions increased by 1.0% to 1.5 Gt CO 2 in 2022 and grew by 2.4% to 1.6 Gt CO 2 in 2023. Meanwhile, emissions began to decrease in other regions. In the United States, emissions increased by 3.0% to 5.0 Gt CO 2 in 2022 but decreased by 2.4% to 4.9 Gt CO 2 in 2023. Similarly, the European Union’s emissions increased by 0.3% to 2.8 Gt CO 2 in 2022 but decreased by 6.2% to 2.6 Gt CO 2 in 2023.

Carbon budget countdown

Global CO 2 emissions are rapidly depleting reported carbon budgets — that is, the amount of carbon that can be released while limiting anthropogenic warming to 1.5 °C and 2 °C above pre-industrial temperatures, as outlined by the Paris Agreement. At 67% likelihood, the IPCC set this budget (starting from 2020 and assuming no overshoot) at 400 Gt CO 2 for 1.5 °C warming 6 . The years 2020, 2021 and 2022 depleted the budget by 9.4% (38 Gt CO 2 ), 9.9% (39 Gt CO 2 ) and 10.0% (40 Gt CO 2 ), respectively, with 2023 emissions using a further 10% (40 Gt CO 2 ). A total of 243 Gt CO 2 remain, which could be exhausted within 6.1 years unless emissions fall sharply. At 83% likelihood, the post-2020 budget to avoid 1.5 °C is only 300 Gt CO 2 . In this case, 2023 emissions depleted 13.3% of the budget, with the remaining 143 Gt CO 2 potentially exhausted within 3.6 years. The carbon budgets for 2 °C warming are larger. At 67% likelihood, the 2°C budget is 1,150 Gt CO 2 , 3.5% of which was used in 2023; the remaining 993 Gt CO 2 could be exhausted within 24.8 years unless growth rates fall. At 83% likelihood, the 2 °C budget is 900 Gt CO 2 , 4.4% of which was used in 2023; 743 Gt CO 2 remains that could be used within 18.6 years.

Other estimates of the remaining carbon budget imply much lower permissible emissions 7 . Under those tighter constraints, only 250 Gt CO 2 or 60 Gt CO 2 remain from January 2023 to achieve the 1.5 °C target at 50% and 66% likelihood, respectively. Accordingly, they convey a more dire timeline. Focusing on the 66% scenario to facilitate comparison with the IPCC likelihoods above, 2023 emissions used 66.7% of the budget, leaving only 20 GtCO 2 ; at the current pace, the entire 1.5 °C target could be depleted halfway through 2024. By comparison, 1,200 Gt CO 2 or 940 Gt CO 2 remains to constrain warming to 2 °C at 50% and 66% likelihood, respectively. For the 66% scenario, 2023 emissions used 4.2% of the budget, leaving 900 Gt CO 2 , which could be diminished within 22.6 years.

Detailed and near-real-time monitoring of CO 2 emissions since 2019 has enabled timely insights into changes in CO 2 emissions worldwide. In 2023, global annual emissions reached an all-time high of 35.8 Gt CO 2 , which reflects a very slight increase of 0.1% year-on-year. While these estimates indicate that post-pandemic emissions growth is slowing, there is not yet convincing evidence of a peak in global emissions — CO 2 emissions continue to rise, particularly in China, India and Russia. Given dwindling carbon budgets to constrain warming to 1.5 °C — the threshold above which climate impacts will become even more disastrous — the absence of a clear downward trend in emissions is troubling. The window of opportunity to meet the most ambitious international climate goals is rapidly closing. Meeting such goals would entail nations accelerating their decarbonization efforts and embracing the consensus from COP28 to “transition away from all fossil fuels in energy systems” as quickly as possible. This call to action is particularly pressing for countries with energy systems heavily reliant on coal, like China, India and Russia, where power generation accounts for approximately half of national carbon emissions. Transitioning these countries’ power sectors away from coal is critical for international climate mitigation efforts. Continued monitoring of global and national carbon emissions could be instrumental in evaluating the efficacy of these efforts.

Liu, Z. et al. Global patterns of daily CO2 emissions reductions in the first year of COVID-19. Nat. Geosci. 15 , 615–620 (2022).

Article   CAS   Google Scholar  

Liu, Z., Deng, Z., Davis, S. J., Giron, C. & Ciais, P. Monitoring global carbon emissions in 2021. Nat. Rev. Earth Environ. 3 , 217–219 (2022).

Article   Google Scholar  

Liu, Z., Deng, Z., Davis, S. & Ciais, P. Monitoring global carbon emissions in 2022. Nat. Rev. Earth Environ. 4 , 205–206 (2023).

Friedlingstein, P. et al. Global Carbon Budget 2023. Earth Syst. Sci. Data 15 , 5301–5369 (2023).

IEA. World Energy Outlook 2023 (IEA, 2023); https://www.iea.org/reports/world-energy-outlook-2023 .

IPCC. Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge Univ. Press, 2021).

Lamboll, R. D. et al. Assessing the size and uncertainty of remaining carbon budgets. Nat. Clim. Change. 13 , 1360–1367 (2023).

Crippa, M. et al. Fossil CO 2 and GHG Emissions of All World Countries - 2020 report . (Publications Office of the European Union, 2020).

Zhu, B. et al. CarbonMonitor-Power near-real-time monitoring of global power generation on hourly to daily scales. Sci. Data 10 , 217 (2023).

Ke, P. et al. Carbon Monitor Europe near-real-time daily CO 2 emissions for 27 EU countries and the United Kingdom. Sci. Data 10 , 374 (2023).

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Institute for Climate and Carbon Neutrality, University of Hong Kong, Hong Kong SAR, China

Zhu Liu & Zhu Deng

Department of Geography, University of Hong Kong, Hong Kong SAR, China

Department of Earth System Science, Tsinghua University, Beijing, China

Alibaba Cloud, Hangzhou, Zhejiang, China

Department of Earth System Science, University of California, Irvine, Irvine, CA, USA

Steven J. Davis

Laboratoire des Sciences du Climat et de l’Environnement LSCE, Gif-sur-Yvette, France

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Buying Time

Warming Is Getting Worse. So They Just Tested a Way to Deflect the Sun.

A spraying machine designed for cloud brightening on the flight deck of the Hornet, a decommissioned aircraft carrier that is now a museum in Alameda, Calif. Credit...

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By Christopher Flavelle

Photographs by Ian C. Bates

Christopher Flavelle reported from a decommissioned aircraft carrier in Alameda, Calif. He spoke with scientists, environmentalists and government officials.

• April 2, 2024

A little before 9 a.m. on Tuesday, an engineer named Matthew Gallelli crouched on the deck of a decommissioned aircraft carrier in San Francisco Bay, pulled on a pair of ear protectors, and flipped a switch.

A few seconds later, a device resembling a snow maker began to rumble, then produced a great and deafening hiss. A fine mist of tiny aerosol particles shot from its mouth, traveling hundreds of feet through the air.

It was the first outdoor test in the United States of technology designed to brighten clouds and bounce some of the sun’s rays back into space, a way of temporarily cooling a planet that is now dangerously overheating. The scientists wanted to see whether the machine that took years to create could consistently spray the right size salt aerosols through the open air, outside of a lab.

If it works, the next stage would be to aim at the heavens and try to change the composition of clouds above the Earth’s oceans.

As humans continue to burn fossil fuels and pump increasing amounts of carbon dioxide into the atmosphere, the goal of holding global warming to a relatively safe level, 1.5 degrees Celsius compared with preindustrial times, is slipping away. That has pushed the idea of deliberately intervening in climate systems closer to reality.

Universities, foundations, private investors and the federal government have started to fund a variety of efforts, from sucking carbon dioxide out of the atmosphere to adding iron to the ocean in an effort to store carbon dioxide on the sea floor.

“Every year that we have new records of climate change, and record temperatures, heat waves, it’s driving the field to look at more alternatives,” said Robert Wood, the lead scientist for the team from the University of Washington that is running the marine cloud brightening project. “Even ones that may have once been relatively extreme.”

Brightening clouds is one of several ideas to push solar energy back into space — sometimes called solar radiation modification, solar geoengineering, or climate intervention. Compared with other options, such as injecting aerosols into the stratosphere, marine cloud brightening would be localized and use relatively benign sea salt aerosols as opposed to other chemicals.

And yet, the idea of interfering with nature is so contentious, organizers of Tuesday’s test kept the details tightly held, concerned that critics would try to stop them. Although the Biden administration is funding research into different climate interventions, including marine cloud brightening, the White House distanced itself from the California study, sending a statement to The New York Times that read: “The U.S. government is not involved in the Solar Radiation Modification (SRM) experiment taking place in Alameda, CA, or anywhere else.”

David Santillo, a senior scientist at Greenpeace International, is deeply skeptical of proposals to modify solar radiation. If marine cloud brightening were used at a scale that could cool the planet, the consequences would be hard to predict, or even to measure, he said.

“You could well be changing climatic patterns, not just over the sea, but over land as well,” he said. “This is a scary vision of the future that we should try and avoid at all costs.”

Karen Orenstein, director of the Climate and Energy Justice Program at Friends of the Earth U.S., a nonprofit environmental group, called solar radiation modification “an extraordinarily dangerous distraction.” She said the best way to address climate change would be to quickly pivot away from burning fossil fuels.

On that last point, the cloud researchers themselves agree.

“I hope, and I think all my colleagues hope, that we never use these things, that we never have to,” said Sarah Doherty, an atmospheric scientist at the University of Washington and the manager of its marine cloud brightening program.

She said there were potential side effects that still needed to be studied, including changing ocean circulation patterns and temperatures, which might hurt fisheries. Cloud brightening could also alter precipitation patterns, reducing rainfall in one place while increasing it elsewhere.

But it’s vital to find out whether and how such technologies could work, Dr. Doherty said, in case society needs them. And no one can say when the world might reach that point.

In 1990, a British physicist named John Latham published a letter in the journal Nature, under the heading “Control of Global Warming?,” in which he introduced the idea that injecting tiny particles into clouds could offset rising temperatures.

Dr. Latham later attributed his idea to a hike with his son in Wales, where they paused to look at clouds over the Irish Sea.

“He asked why clouds were shiny at the top but dark at the bottom,” Dr. Latham told the BBC in 2007 . “I explained how they were mirrors for incoming sunlight.”

Dr. Latham had a proposal that may have seemed bizarre: create a fleet of 1,000 unmanned, sail-powered vessels to traverse the world’s oceans and continuously spray tiny droplets of seawater into the air to deflect solar heat away from Earth.

The idea is built on a scientific concept called the Twomey effect: Large numbers of small droplets reflect more sunlight than small numbers of large droplets. Injecting vast quantities of minuscule aerosols, in turn forming many small droplets, could change the composition of clouds.

“If we can increase the reflectivity by about 3 percent, the cooling will balance the global warming caused by increased C02 in the atmosphere,” Dr. Latham, who died in 2021 , told the BBC. “Our scheme offers the possibility that we could buy time.”

A version of marine cloud brightening already happens every day, according to Dr. Doherty.

As ships travel the seas, particles from their exhaust can brighten clouds, creating “ship tracks,” behind them. In fact, until recently, the cloud brightening associated with ship tracks offset about 5 percent of climate warming from greenhouse gases, Dr. Doherty said.

Ironically, as better technology and environmental regulations have reduced the pollution emitted by ships, that inadvertent cloud brightening is fading, as well as the cooling that goes along with it.

A deliberate program of marine cloud brightening could be done with sea salts, rather than pollution, Dr. Doherty said.

Brightening clouds is no easy task. Success requires getting the size of the aerosols just right: Particles that are too small would have no effect, said Jessica Medrado, a research scientist working on the project. Too big and they could backfire, making clouds less reflective than before. The ideal size are submicron particles about 1/700th the thickness of a human hair, she said.

Next, you need to be able to expel a lot of those correctly sized aerosols into the air: A quadrillion particles, give or take, every second. “You cannot find any off-the-shelf solution,” Dr. Medrado said.

The answer to that problem came from some of the most prominent figures in America’s technology industry.

In 2006, the Microsoft founder, Bill Gates, got a briefing from David Keith, one of the leading researchers in solar geoengineering, which is the idea of trying to reflect more of the sun’s rays. Mr. Gates began funding Dr. Keith and Ken Caldeira, another climate scientist and a former software developer, to further their research.

The pair considered the idea of marine cloud brightening but wondered if it was feasible.

So they turned to Armand Neukermans, a Silicon Valley engineer with a doctorate in applied physics from Stanford and 74 patents. One of his early jobs was at Xerox, where he devised a system to produce and spray ink particles for copiers. Dr. Caldeira asked if he could develop a nozzle that would spray not ink, but sea salt aerosols.

Intrigued, Dr. Neukermans, who is now 83, lured some of his old colleagues out of retirement and began research in a borrowed lab in 2009, with $300,000 from Mr. Gates. They called themselves the Old Salts.

The team worked on the problem for years, eventually landing on a solution: By pushing air at extremely high pressure through a series of nozzles, they could create enough force to smash salt crystals into exceedingly small particles of just the right size.

Their work moved to a larger laboratory at the Palo Alto Research Center, a former Xerox research facility now owned by SRI International, a independent nonprofit research institute. Dr. Medrado became the lead engineer for the project two years ago. By the end of last year, the sprayer had been assembled and was waiting in a warehouse near San Francisco.

The machine was ready. The team needed somewhere to test it.

As the researchers were perfecting the sprayer, a profound transformation was happening outside their laboratory.

Since Dr. Latham first proposed the idea of marine cloud brightening, the concentration of heat-trapping gases in the atmosphere has increased by about 20 percent. Last year was the hottest in recorded history and the World Meteorological Organization projects that 2024 will be another record year . Global ocean temperatures have been at record highs for the past year.

As the effects of climate change continue to grow, so has interest in some sort of backup plan. In 2020, Congress directed the National Oceanic and Atmospheric Administration to study solar radiation modification. In 2021, the National Academies of Sciences, Engineering and Medicine published a report saying the United States should “cautiously pursue” research into the idea. Last month, scientists from NOAA and other federal agencies proposed a road map for researching marine cloud brightening.

Interest is growing overseas, as well. In February, an Australian team of researchers at Southern Cross University, which was advised by Dr. Neukermans, conducted a monthlong experiment off the country’s northeast coast, spraying aerosols from a ship and measuring the response of clouds.

Daniel P. Harrison, the lead researcher, called the tests “the smallest of baby steps aimed at confirming and refining the underpinning theory in the real world.” He said it was too early to discuss any findings.

Private funding is also growing. Kelly Wanser is a former technology executive who helped establish the marine cloud brightening project at the University of Washington. In 2018 she created SilverLining , a nonprofit organization to advance research into what she calls “near-term climate interventions” like cloud brightening.

Ms. Wanser’s group is contributing part of the funding for the research at the University of Washington and SRI, which is budgeted at about $10 million over three years, she said. That includes the study aboard the Hornet, which is expected to cost about $1 million a year.

Finding money for that work has gotten easier as record heat has “really shifted attitudes” among funders, Ms. Wanser said. Donors include the Quadrature Climate Foundation, the Pritzker Innovation Fund and the Cohler Charitable Fund, established by the former Facebook executive Matt Cohler, according to Ms. Wanser.

Last year, Ms. Wanser spoke with a member of the board that runs the Hornet, which now operates as a museum affiliated with the Smithsonian. Would they host a first-of-its-kind study?

The museum agreed. The test was a go.

The flight deck of the Hornet rises 50 feet above the shore of Alameda, a small town on the east side of San Francisco Bay. On Tuesday, it held a series of finely calibrated sensors, perched atop a row of scissor lifts reaching into the air.

Underneath a United States flag at the far end of the flight deck was the sprayer: Shiny blue, roughly the shape and size of a spotlight, with a ring of tiny steel nozzles around its three-foot-wide mouth. The researchers call it CARI, for Cloud Aerosol Research Instrument.

On one side of the sprayer was a box the size of a shipping container that housed a pair of compressors, which fed highly pressurized air to the sprayer through a thick, black hose. On the other side was a tank of water. A series of switches, turned in careful sequence, fed the water and air into the device, which then shot a fine mist toward the sensors.

The goal was to determine whether the aerosols leaving the sprayer, which had been carefully manipulated to reach a specific size, remained that size as they rushed through the air in different wind and humidity conditions. It will take months to analyze the results. But the answers could determine whether marine cloud brightening would work, and how, according to Dr. Wood.

Ms. Wanser said she hoped the testing, which could continue for months or longer, will demystify the concept of climate intervention technologies. Toward that aim, the equipment will remain on the Hornet and be on display during hours when the ship is open to the public. Even if the equipment is not ultimately used to cool the planet, the data it generates can add to the understanding of how pollution and other aerosols interact with clouds, the researchers said.

Dr. Wood estimated that scientists could need another decade of tests before they were in a position to potentially use marine cloud brightening at the scale required to cool the Earth.

Ms. Wanser is already looking ahead to the next phase of that research. “The next step is go out to the ocean,” she said, “aim up the spray a little higher, and touch clouds.”

Christopher Flavelle is a Times reporter who writes about how the United States is trying to adapt to the effects of climate change. More about Christopher Flavelle

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