Last year was the warmest since records began in the mid-1800s – and likely for many thousands of years before.
It was the first year in which average global temperatures at the surface exceeded 1.5C above pre-industrial levels in at least one global temperature dataset.
Here, Carbon Brief examines the latest data across the oceans, atmosphere, cryosphere and surface temperature of the planet.
Noteworthy findings from this 2023 review include…
- Global surface temperatures: It was the warmest year on record by a large margin – at between 1.34C and 1.54C above pre-industrial levels across different temperature datasets.
- Exceptional monthly temperatures: Global temperatures set a new record each month between June and December. September smashed the prior record for the month by a “gobsmacking” 0.5C.
- Warmest over land: It was the first year the global average land temperature was more than 2C above pre-industrial levels.
- Warmest over oceans: It was the first year that global average ocean surface temperatures exceeded 1C compared with pre-industrial levels.
- Ocean heat content: It was the warmest year on record for ocean heat content, which increased notably between 2022 and 2023.
- Regional warming: It was the warmest year on record in 77 countries – including China, Brazil, Austria, Bangladesh, Germany, Greece, Ireland, Japan, Mexico, the Netherlands, South Korea and Ukraine – and in areas where 2.3 billion people live.
- Unusual warmth: 2023 was much warmer than scientists estimated it would be at the start of the year and there remain open questions about what precise factors have driven the exceptional warmth. Even El Niño – the usual suspect behind record warm years – does not clearly explain 2023 temperatures.
- Comparison with climate models: Observations for 2023 are above the central estimate of climate model projections in the Intergovernmental Panel on Climate Change (IPCC) sixth assessment report, but well within the model range.
- Warming of the atmosphere: It was the warmest year in the lower troposphere – the lowest part of the atmosphere. The stratosphere – in the upper atmosphere – is cooling, due in part to heat trapped in the lower atmosphere by greenhouse gases.
- Sea level rise: Sea levels reached new record-highs, with notable acceleration over the past three decades.
- Shrinking glaciers and ice sheets: Cumulative ice loss from the world’s glaciers and from the Greenland ice sheet reached a new record high in 2023, contributing to sea level rise.
- Greenhouse gases: Concentrations reached record levels for CO2, methane and nitrous oxide.
- Sea ice extent: Arctic sea ice saw its sixth-lowest minimum extent on record, while Antarctic sea ice saw a new record low extent for almost the entire year, much of it by an exceptionally large margin.
- Looking ahead to 2024: Carbon Brief predicts that global average surface temperatures in 2024 are most likely to be slightly warmer than 2023 and set a new all-time record. However, large uncertainties remain given how exceptionally and unexpectedly warm 2023 was.
Use the links below to navigate between the article’s sections.
- Warmest year on record for the Earth’s surface
- Pushing up against the 1.5C target
- Highest ocean heat content on record
- A year of climate extremes
- Explaining 2023’s unusual heat
- Observations broadly in-line with climate model projections
- Record atmospheric temperatures
- Greenhouse gas concentrations reach new highs
- Accelerating sea level rise
- Shrinking glaciers and ice sheets
- Record-low Antarctic sea ice levels
- Looking ahead to 2024
Warmest year on record for the Earth’s surface
Global surface temperatures were exceptionally hot in 2023, exceeding the prior record set in 2016 by between 0.14C and 0.17C across different surface temperature datasets. It was unambiguously the warmest year since records began in the mid-1800s.
The figure below shows global surface temperature records from five different datasets: NASA; NOAA; the Met Office Hadley Centre/University of East Anglia’s (UEA) HadCRUT5; Berkeley Earth; and Copernicus ERA5.
Other surface temperature datasets not shown, including JRA-55, the AIRS satellite data and the Japanese Meteorological Agency, also show 2023 as the warmest year on record.
Annual global average surface temperatures over 1850-2023. Data from NASA GISTEMP, NOAA GlobalTemp, Hadley/UEA HadCRUT5, Berkeley Earth and Copernicus ERA5. Temperature records are aligned over the 1981-2010 period and use the average of NOAA, Berkeley and Hadley records to calculate warming relative to the pre-industrial baseline. Chart by Carbon Brief.
Global surface temperature records can be calculated back to 1850, though some groups such as NASA GISTEMP 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 high accuracy (though work is ongoing to identify and digitise additional records to extend these further back in time).
These longer surface temperature 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 and JRA-55 are an exception, as they use weather model-based reanalysis to combine lots of different data sources over time.)
Some differences between temperature records are apparent early in the record, particularly prior to 1900 when observations are more sparse and results are more sensitive to how different groups fill in the gaps between observations. However, there is excellent agreement between the different temperature records for the period since 1970, as shown in the figure below.
Annual global average surface temperatures as in the prior chart, but showing the period from 1970-2023. Chart by Carbon Brief.
Global temperatures in 2023 clearly 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).
The year 2023 was the warmest on record for both the world’s land and ocean regions.
It was also the first year where global average land temperatures exceeded 2C and the first year in which global ocean temperatures exceeded 1C relative to pre-industrial levels.
The figure below shows land (red) and ocean (blue) temperatures along with their respective confidence intervals, relative to pre-industrial levels, in the Berkeley Earth surface temperature record.
Global land regions – where the global human population lives – has been warming around 70% faster than the oceans – and 40% faster than the global average in the years since 1970.
While 2023 as a whole has been exceptionally warm, it started off a bit cooler, with the first few months of the year failing to set any new records. However, from June onward each month was warmer than the same month in any prior year since records began. September was particularly “gobsmacking”, shattering the prior September record by a full 0.5C.
The figure below shows each month of 2023 in black, compared to all prior years since 1850. Each year is coloured based on the decade in which it occurred, with the clear warming over time visible as well as the exceptional margin by which 2023 exceeded past years between July and December.
Pushing up against the 1.5C target
In the 2015 Paris Agreement, the world agreed to work to limit global temperatures to well-below 2C and to pursue efforts to “limit the temperature increase to 1.5C above pre-industrial levels”.
While the exceedance of these climate targets was not specifically defined in the agreement, it has since been widely interpreted (for example, by the IPCC) as a 20-year average period.
Crucially, the limits refer to long-term warming, rather than an individual year that includes the short-term influence of natural fluctuations in the climate, such as El Niño.
However, a single year exceeding 1.5C still represents a grim milestone, a sign that the world is quickly approaching the target. And, in the Berkeley Earth dataset, 2023 was the first year above 1.5C.
It came in a hair’s width below 1.5C in the Copernicus and Hadley datasets, at 1.48C and 1.46C, respectively, and was lower on NOAA and NASA datasets as shown in the table below.
| Temperature record | 2023 temperatures relative to preindustrial |
|---|---|
| NOAA GlobalTemp | 1.34C |
| NASA GISTEMP | 1.39C* |
| Hadley/UAE HadCRUT5 | 1.46C |
| Copernicus/ECMWF | 1.48C |
| Berkeley Earth | 1.54C |
Global temperature anomalies for 2023 relative to preindustrial temperatures (1850-1899). *Note that GISTEMP uses a 1880-1899 baseline as it does not cover the 1850-1879 period.
As noted earlier, these datasets are nearly identical over the past 50 years. Differences in warming relative to pre-industrial levels emerge earlier in the record, particularly prior to 1900 when observations are more sparse and the choice of how to fill in the gaps between observations has a large impact on the resulting temperature estimate.
The figure below shows how different temperature records look if each is calculated relative to its own pre-industrial baseline, rather than using an average pre-industrial baseline as shown in the prior section. Focusing on warming since pre-industrial – rather than more recent warming – magnifies differences between groups, with the variation in warming across groups largely due to the most uncertain early part of the record.
Highest ocean heat content on record
Last year was the warmest on record for the heat content of the world’s oceans. Ocean heat content (OHC) has increased by around 473 zettajoules – a billion trillion joules – since the 1940s. The heat increase in 2023 alone compared to 2021 – about 15 zettajoules – is around 25 times as much as the total energy produced by all human activities on Earth in 2021 (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.
The figure below shows annual OHC estimates between 1950 and present for both the upper 700 metres (light blue shading) and 700-2,000 metres (dark blue) of the ocean.
Annual global ocean heat content (in zettajoules – billion trillion joules, or 10^21 joules) for the 0-700 metre and 700-2,000 metre layers. Data from Cheng et al. (2024). Chart by Carbon Brief.
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. It shows a distinct acceleration after 1991, matching the increased rate of greenhouse gas emissions and other radiative forcing elements over the past few decades.
This year saw a substantial update to the OHC dataset provided by the Institute for Atmospheric Physics (IAP) that Carbon Brief features in its State of the Climate reports. The transition from version 3 to version 4 introduced a new quality control system to detect and remove spurious measurements across different instrument types.
As the figure below highlights, this results in a notable increase in OHC over the past decade (red lines and shading) relative to the prior version of the dataset (black lines).
A year of climate extremes
While media coverage of 2023 temperatures has largely focused on the global average, there have been many different regions of the planet experiencing climate extremes.
The figure below shows global temperature anomalies in 2023 across the world, with red areas warmer than the baseline period (1951-80) used by Berkeley Earth and blue areas experiencing cooler temperatures.
In 2023, 77 countries saw their warmest year on record, including: Afghanistan, Albania, Antigua and Barbuda, Argentina, Austria, Azerbaijan, Bangladesh, Bhutan, Bolivia, Bosnia and Herzegovina, Brazil, Bulgaria, Cape Verde, Cameroon, China, Comoros, Costa Rica, Croatia, Cuba, Czechia, Dominica, Dominican Republic, Ecuador, El Salvador, Federated States of Micronesia, Gambia, Germany, Greece, Grenada, Guatemala, Guinea, Guyana, Haiti, Honduras, Hungary, Ireland, Ivory Coast, Jamaica, Japan, Kazakhstan, Kiribati, Kosovo, Kyrgyzstan, Liechtenstein, Macedonia, Mexico, Moldova, Montenegro, Morocco, Myanmar, Netherlands, Nicaragua, Nigeria, North Korea, Oman, Panama, Paraguay, Peru, Republic of the Congo, Romania, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, San Marino, Senegal, Serbia, Slovakia, Slovenia, South Korea, Tajikistan, The Bahamas, Trinidad and Tobago, Turkmenistan, Ukraine, Uzbekistan, Venezuela and Yemen.
Approximately 2.3 billion people, or around 29% of Earth’s population, live in places that observed their locally warmest year during 2023.
The figure below highlights regions of the planet that experienced their top-five warmest (red shading) or coldest (blue) temperatures on record in 2023. Overall, around 17% of the planet set a new record, including 23% of the land and 14% of the ocean. No location on the planet experienced record cold temperatures (or even top-5 record cold temperatures) for the year as a whole.
Explaining 2023’s unusual heat
Scientists did not expect 2023 to be all that exceptional at the start of the year. As Carbon Brief reported at the start of 2023, four different groups provided temperature predictions for the year prior to any data being collected – the UK Met Office, NASA’s Dr Gavin Schmidt, Berkeley Earth and Carbon Brief’s own estimate.
Temperature predictions for 2023 from the UK Met Office, NASA’s Dr Gavin Schmidt, Berkeley Earth and Carbon Brief relative to pre-industrial (1880-99) temperatures. Chart by Carbon Brief.
As Carbon Brief noted in January 2023:
“La Niña conditions are expected to persist for at least the first three months of 2023. 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 lingering cooling influence on 2023 temperatures.”
Carbon Brief estimated that 2023 was “very likely to be between the third and ninth warmest year on record, with a best estimate of being the fifth warmest on record – similar to 2022”, and suggest that if an El Niño develops in latter half of 2023 it would make it likely that 2024 will set a new record.
This estimate, alongside all the other groups predicting 2023 temperatures, was wrong. Not only did 2023 turn out to be the warmest year on record, but it fell well outside the confidence intervals of any of the estimates. And while there are a number of factors that researchers have proposed to explain 2023’s exceptional warmth, scientists still lack a clear explanation for why global temperatures were so unexpectedly high.
Over the longer-term, human emissions of CO2 and other greenhouse gases alongside planet-cooling aerosols are the main driver of global temperatures. Global temperatures have risen by approximately 1.3C since pre-industrial times as a result of human activity. However, on top of long-term warming, global temperatures vary year to year by up to 0.2C.
These variations are primarily driven by El Niño and La Niña events that redistribute heat between the atmosphere and oceans. However, other factors such as volcanic eruptions, the 11-year solar cycle and changes in short-lived climate forcers can influence year-to-year temperature changes.
The figure below, created by Dr Robert Rohde at Berkeley Earth, explores some of the main drivers of temperature change over the past decade.
These include continued accumulation of greenhouse gases, the evolution of El Niña and La Niña, and the 11-year solar cycle. It also includes two new factors that emerged during the decade: the 2022 eruption of the Hunga Tonga volcano and the 2020 phase-out of sulphur in marine fuels. Both of these are estimated to have relatively modest effects at present – less than 0.05C each – but with large scientific uncertainties.
However, both the Tonga eruption and the phase-out of sulphur in marine fuel are problematic explanations of extreme temperatures in 2023.
There is still a vigorous debate in the scientific literature about whether the eruption cooled or warmed the planet based on estimates of both sulphur dioxide and water vapour in the atmosphere, with some papers arguing for warming and others for cooling. Some modelling suggests that the largest impacts of the eruption would be in winter months, which does not match the timing of extreme summer temperatures experienced in 2023.
Similarly, the phase-out of sulphur in marine fuels occurred in 2020. If it had a large climate impact, it would show up in 2021 and 2022 rather than suddenly affecting the record in 2023. While it definitely has had a climate impact – alongside the broader reduction in aerosol emissions over the past three decades – the timing suggests that its likely not the primary driver of 2023 extremes.
Even El Niño – the usual suspect behind record warm years – does not clearly explain 2023 temperatures. Historically global temperatures have lagged around three months behind El Niño conditions in the tropical Pacific; for example, El Niño developed quite similarly in 1997, 2015 and 2023. But it was the following year – 1998 and 2016 – that saw record high temperatures.
The figure below shows the El Niño (red shading) and La Niña (blue) conditions over the past 40 years (collectively referred to as the El Niño-Southern Oscillation, or “ENSO”). While not unprecedented, the extended La Niña conditions since the latter part of 2020 have extended for an unusually long period of time.
Carbon Brief has used this historical relationship between ENSO conditions and temperature to effectively remove the effects of El Niño and La Niña events from global temperatures, as shown in the figure below.
However, this approach – which has worked well for prior years – indicates that there would be almost no effect of El Niño on temperatures in 2023. This is because the lingering global temperature impact of La Niña conditions on the first half of the year would approximately cancel out the influence of El Niño on the second half. This model would suggest that the current El Niño event would primarily affect 2024 temperatures, analogous to what occurred in 1998 and 2016.
Annual global average surface temperatures from Berkeley Earth, as well as Carbon Brief’s estimate of global temperatures with the effect of El Niño and La Niña (ENSO) events removed using the Foster and Rahmstorf (2011) approach. Figures are shown relative to a 1981-2010 baseline. Chart by Carbon Brief.
It is possible that this El Niño event is behaving differently and that the rapid switch from a rare and extended triple-dip La Niña event from late 2020 to the start of this year into strong El Niño conditions is resulting in a more rapid global temperature response.
But this remains speculative at this point and researchers are just starting to disentangle the causes of the unexpected extreme global heat the world experienced in 2023.
Observations broadly in-line with 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 CMIP6 – used in the 2021 science report of the IPCC’s sixth assessment. In CMIP6, model estimates of temperatures prior to 2015 are a “hindcast” using known past climate influences, while temperatures projected after 2015 are a “forecast” based on an estimate of how things might change.
Using the CMIP6 ensemble is a bit more challenging than past generations of models because a subset of models have unrealistically high climate sensitivity and poorly reproduce historical observations. Rather than simply average all the models – as had been done in prior assessments – the IPCC used an approach that effectively weights models by their performance. This means the models align better with the range of climate sensitivity derived from multiple different lines of evidence.
The figure below shows the range of individual CMIP6 model projections since 1950, as well as future projections through to 2100 under the middle-of-the-road SSP2-4.5 emissions scenario.
The black line shows the average of 22 different models whose transient climate response (TCR) falls within the IPCC’s “likely” range (which results in temperature projections nearly identical to the IPCC assessed warming). The grey area shows the 95% (two standard deviation) range of the TCR-screened model projections. Observational temperatures are plotted on top of the climate model data, with individual observational records represented by coloured lines.
Annual global average surface temperatures from CMIP6 models and observations between 1950 and 2030 (through to 2023 for observations). Models use the SSP2-4.5 scenario after 2015. They are screened to only include those models with a transient climate response (TCR) in-line with the IPCC’s “likely” range as discussed in Hausfather et al (2022). Anomalies plotted with respect to a 1981-2010 baseline. Chart by Carbon Brief.
Using the TCR-screened subset, the findings show that 2023 temperatures are above the model average, but still well within the range of climate model projections. While some individual months have approached the upper end of the model range, the year as a whole is less anomalous.
The figure below shows the observed warming since pre-industrial (1850-99) in the five different observational datasets compared with climate model projections. The box plot below shows the 25th to 75th percentile of models and observations with a solid box, while the whiskers show 1.5 times the interquartile range.
Temperatures in 2023, relative to pre-industrial, were in the upper quartile (>75th percentile) of climate models assessed. However, this is not unexpected, as models do not have internal variability such as El Niño or La Niña events that occur at the same time as they do in the real world. (Scientists would expect observations to be on the high end of the model range during El Niño years and on the low end in La Niña years even if climate models were perfectly accurate.)
Finally, the figure below shows how observations compare to the full ensemble of 37 CMIP6 models, with no screening for transient climate response. Here, observations are generally below the model average over the past two decades and are roughly equal to the model average in 2023.
Annual global average surface temperatures from CMIP6 models and observations between 1950 and 2030 (through 2023 for observations). Models use the SSP2-4.5 scenario after 2015. Anomalies plotted with respect to a 1981-2010 baseline. Chart by Carbon Brief.
Record atmospheric temperatures
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 shows a pattern of warming similar – though not identical – to surface temperature changes. The records produced by Remote Sensing Systems (RSS) and the University of Alabama, Huntsville (UAH) both show 2023 as the warmest year on record in the lower troposphere. The chart below shows the two records – RSS in red and UAH in blue – for the lower troposphere (TLT).
Global average lower-troposphere temperatures from RSS version 4 (red) and UAH version 6 (blue) for the period from 1979-2023, relative to a 1981-2010 baseline. Chart by Carbon Brief.
The lower troposphere tends to be influenced more strongly by El Niño and La Niña events than the surface. Therefore, 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.
Overall, there is more agreement with RSS to other records that include satellite data (such as reanalysis products ERA5 and JRA-55, as well as the shorter AIRS satellite-based surface temperature record), while the UAH record is a bit of an outlier compared to the others.
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 figure below shows lower stratospheric temperature (TLS) records for both RSS (red) and UAH (blue) from 1979 through 2023.
Global average lower stratospheric temperatures from RSS version 4 (red) and UAH version 6 (blue) for the period from 1979-2023, relative to a 1981-2010 baseline. Chart by Carbon Brief.
The stratosphere has been cooling for the past 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.
Greenhouse gas concentrations reach new highs
Greenhouse gas concentrations reached a new high in 2023, 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 42% of the increase in global surface temperatures since the pre-industrial era (1850-1900).
Methane accounts for 28%, while nitrous oxide accounts for around 5%. The remaining 25% 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 2023 for CO2 and September 2023 for CH4 and N2O (the most recent data currently available).
Global concentrations of CO2, methane (CH4) and nitrous oxide (N2O). Based on data from NOAA’s Earth Systems Research Laboratory. Note that the y-axes do not start at zero. Chart by Carbon Brief.
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. Thawing Arctic permafrost and other sources of methane in high-latitude regions are growing, but emissions above a latitude of 60 degrees north are only around 4% of the total global methane emissions.
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 five different modern 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 2023 value is estimated based on data through October.)
Global average sea level rise reconstructed from tide gauge data between 1880 and 2023 from Frederikse et al 2020, Dangendorf et al 2019, Hay et al 2015, Church and White 2011, and Palmer et al 2021. Satellite altimeter data from 1993 (black) to present is taken from the University of Colorado. Chart by Carbon Brief.
Sea levels have risen by over 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.)
Shrinking glaciers and ice sheets
A portion of this sea level rise is being driven by melting glaciers on land. 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.
The World Glacier Monitoring Service is an international consortium that 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 2022 (2023 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.
Global average glacier melt over the 1950-2022 period from the World Glacier Monitoring Service, in metres of water equivalent. Carbon Brief.
Greenland ice sheets have become a larger contributor to sea level rise in recent years due to accelerating loss of mass. The year 2023 was the 27th in a row where Greenland lost ice overall, with 196Gt of ice lost over the 12 months from September 2022 to August 2023. Greenland last saw an annual net gain of ice in 1996.
The figure below shows the cumulative mass balance change – that is, the net ice loss – from Greenland between 1970 and October 2021. The different coloured lines indicate estimates from different studies. The authors find that Greenland has lost over 6tn metric tonnes of ice over the past 50 years – more than 700 tonnes lost per person for every person on the planet.
Cumulative ice loss from Greenland in billion metric tonnes (gigatonnes) between 1970 and 2023 from Mankoff et al 2021, updated through December 2023. Chart by Carbon Brief.
Record-low Antarctic sea ice levels
Arctic sea ice was at the low end of the historical (1979-2010) range for most of 2023, but did not set any new all-time low records apart from a few individual days in February and March. The summer minimum extent – the lowest recorded level for the year – was the sixth-lowest since records began in the late 1970s.
Antarctic sea ice, on the other hand, saw new record low levels for virtually the entire year – except for periods in April, November and December of the year.
Antarctic sea ice was particularly low between June and November, shattering prior records by a substantial margin. While long-term trends in Antarctic sea ice have been ambiguous in the past (unlike in the Arctic where there is a consistent long-term decline), there is increasing evidence that human-driven warming is starting to drive significant loss of sea ice in the region.
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).
Arctic and Antarctic daily sea ice extent from the US National Snow and Ice Data Center. The bold lines show daily 2023 values, the shaded area indicates the two standard deviation range in historical values between 1979 and 2010. The dotted black lines show the record lows for each pole. Chart by Carbon Brief.
Looking ahead to 2024
The unusual global temperatures experienced in 2023 makes it more challenging to predict what 2024 might have in store.
If history is any guide here, the year after the development of an El Niño event tends to be considerably warmer than the year in which it develops. For example, strong El Niño events developed over the latter half of both 1997 and 2015 and peaked early the following year, and 1998 and 2016 both set new records by a large margin.
However, 2023 was so exceptionally warm that it suggests that this El Niño might be behaving differently, with global surface temperatures responding more rapidly than in the past. If this is the case, 2024 would not necessarily follow the pattern of past El Niño events and is less likely to be substantially warmer than 2023.
There have been four published predictions – from the UK Met Office, NASA’s Dr Gavin Schmidt, Berkeley Earth and Carbon Brief (in this article) – of what temperatures might look like in 2024.
The figure below shows the four different 2024 predictions compared to the average of six different temperature records (NASA, NOAA, Hadley, Berkeley, Copernicus, and the Japanese JRA-55 reanalysis) used by the World Meteorological Organization (WMO). These have been “normalised” to show 2024 warming relative to 2023 in the WMO dataset. This is to remove any differences in predictions due to divergences in the baselines used by different temperature records.
Carbon Brief’s prediction of likely 2024 temperatures is based on a statistical model using the year, the average temperature of the past year, and projections of El Niño/La Niña conditions over the first three months to predict the temperatures of the year.
Temperature projections for 2024 from the UK Met Office, NASA’s Dr Gavin Schmidt, Berkeley Earth, and Carbon Brief, relative to pre-industrial (1880-99) temperatures and compared to the historical average of six different datasets produced by the WMO. Chart by Carbon Brief.
The Met Office, Dr Schmidt, Berkeley Earth and Carbon Brief estimates all have 2024 as more likely than not to be warmer than 2023 – but only by a small margin. In all estimates it is close to a coin flip which will end up as the warmer year.
Against a 1880-99 pre-industrial baseline, the central estimate of all four forecasts is just below 1.5C of warming, with ranges suggesting that temperatures could top 1.5C next year.
However, the poor performance by all of these groups in accurately predicting 2023 temperatures mean these should be treated with some caution. Until scientists have a clearer understanding of the drivers of the unusual warmth the world experienced in 2023, it will not be possible to fully predict how temperatures will evolve in 2024 as the current El Niño event peaks and fades away.
Ultimately, 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.
As the chart below highlights, if the warming trend over the past 40 years continues, average surface temperatures are likely to pass 1.5C in the early 2030s and 2C by around 2060.
The post State of the Climate: 2023 smashes records for surface temperature and ocean heat appeared first on Carbon Brief.
State of the Climate: 2023 smashes records for surface temperature and ocean heat
Climate Change
DeBriefed 9 January 2026: US to exit global climate treaty; Venezuelan oil ‘uncertainty’; ‘Hardest truth’ for Africa’s energy transition
Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.
This week
US to pull out from UNFCC, IPCC
CLIMATE RETREAT: The Trump administration announced its intention to withdraw the US from the world’s climate treaty, CNN reported. The move to leave the UN Framework Convention on Climate Change (UNFCCC), in addition to 65 other international organisations, was announced via a White House memorandum that states these bodies “no longer serve American interests”, the outlet added. The New York Times explained that the UNFCCC “counts all of the other nations of the world as members” and described the move as cementing “US isolation from the rest of the world when it comes to fighting climate change”.
MAJOR IMPACT: The Associated Press listed all the organisations that the US is exiting, including other climate-related bodies such as the Intergovernmental Panel on Climate Change (IPCC) and the International Renewable Energy Agency (IRENA). The exit also means the withdrawal of US funding from these bodies, noted the Washington Post. Bloomberg said these climate actions are likely to “significantly limit the global influence of those entities”. Carbon Brief has just published an in-depth Q&A on what Trump’s move means for global climate action.
Oil prices fall after Venezuela operation
UNCERTAIN GLUT: Global oil prices fell slightly this week “after the US operation to seize Venezuelan president Nicolás Maduro created uncertainty over the future of the world’s largest crude reserves”, reported the Financial Times. The South American country produces less than 1% of global oil output, but it holds about 17% of the world’s proven crude reserves, giving it the potential to significantly increase global supply, the publication added.
TRUMP DEMANDS: Meanwhile, Trump said Venezuela “will be turning over” 30-50m barrels of oil to the US, which will be worth around $2.8bn (£2.1bn), reported BBC News. The broadcaster added that Trump claims this oil will be sold at market price and used to “benefit the people of Venezuela and the US”. The announcement “came with few details”, but “marked a significant step up for the US government as it seeks to extend its economic influence in Venezuela and beyond”, said Bloomberg.
Around the world
- MONSOON RAIN: At least 16 people have been killed in flash floods “triggered by torrential rain” in Indonesia, reported the Associated Press.
- BUSHFIRES: Much of Australia is engulfed in an extreme heatwave, said the Guardian. In Victoria, three people are missing amid “out of control” bushfires, reported Reuters.
- TAXING EMISSIONS: The EU’s landmark carbon border levy, known as “CBAM”, came into force on 1 January, despite “fierce opposition” from trading partners and European industry, according to the Financial Times.
- GREEN CONSUMPTION: China’s Ministry of Commerce and eight other government departments released an action plan to accelerate the country’s “green transition of consumption and support high-quality development”, reported Xinhua.
- ACTIVIST ARRESTED: Prominent Indian climate activist Harjeet Singh was arrested following a raid on his home, reported Newslaundry. Federal forces have accused Singh of “misusing foreign funds to influence government policies”, a suggestion that Singh rejected as “baseless, biased and misleading”, said the outlet.
- YOUR FEEDBACK: Please let us know what you thought of Carbon Brief’s coverage last year by completing our annual reader survey. Ten respondents will be chosen at random to receive a CB laptop sticker.
47%
The share of the UK’s electricity supplied by renewables in 2025, more than any other source, according to Carbon Brief analysis.
Latest climate research
- Deforestation due to the mining of “energy transition minerals” is a “major, but overlooked source of emissions in global energy transition” | Nature Climate Change
- Up to three million people living in the Sudd wetland region of South Sudan are currently at risk of being exposed to flooding | Journal of Flood Risk Management
- In China, the emissions intensity of goods purchased online has dropped by one-third since 2000, while the emissions intensity of goods purchased in stores has tripled over that time | One Earth
(For more, see Carbon Brief’s in-depth daily summaries of the top climate news stories on Monday, Tuesday, Wednesday, Thursday and Friday.)
Captured
The US, which has announced plans to withdraw from the UNFCCC, is more responsible for climate change than any other country or group in history, according to Carbon Brief analysis. The chart above shows the cumulative historical emissions of countries since the advent of the industrial era in 1850.
Spotlight
How to think about Africa’s just energy transition
African nations are striving to boost their energy security, while also addressing climate change concerns such as flood risks and extreme heat.
This week, Carbon Brief speaks to the deputy Africa director of the Natural Resource Governance Institute, Ibrahima Aidara, on what a just energy transition means for the continent.
Carbon Brief: When African leaders talk about a “just energy transition”, what are they getting right? And what are they still avoiding?
Ibrahima Aidara: African leaders are right to insist that development and climate action must go together. Unlike high-income countries, Africa’s emissions are extremely low – less than 4% of global CO2 emissions – despite housing nearly 18% of the world’s population. Leaders are rightly emphasising universal energy access, industrialisation and job creation as non-negotiable elements of a just transition.
They are also correct to push back against a narrow narrative that treats Africa only as a supplier of raw materials for the global green economy. Initiatives such as the African Union’s Green Minerals Strategy show a growing recognition that value addition, regional integration and industrial policy must sit at the heart of the transition.
However, there are still important blind spots. First, the distributional impacts within countries are often avoided. Communities living near mines, power infrastructure or fossil-fuel assets frequently bear environmental and social costs without sharing in the benefits. For example, cobalt-producing communities in the Democratic Republic of the Congo, or lithium-affected communities in Zimbabwe and Ghana, still face displacement, inadequate compensation, pollution and weak consultation.
Second, governance gaps are sometimes downplayed. A just transition requires strong institutions (policies and regulatory), transparency and accountability. Without these, climate finance, mineral booms or energy investments risk reinforcing corruption and inequality.
Finally, leaders often avoid addressing the issue of who pays for the transition. Domestic budgets are already stretched, yet international climate finance – especially for adaptation, energy access and mineral governance – remains far below commitments. Justice cannot be achieved if African countries are asked to self-finance a global public good.
CB: Do African countries still have a legitimate case for developing new oil and gas projects, or has the energy transition fundamentally changed what ‘development’ looks like?
IA: The energy transition has fundamentally changed what development looks like and, with it, how African countries should approach oil and gas. On the one hand, more than 600 million Africans lack access to electricity and clean cooking remains out of reach for nearly one billion people. In countries such as Mozambique, Nigeria, Senegal and Tanzania, gas has been framed to expand power generation, reduce reliance on biomass and support industrial growth. For some contexts, limited and well-governed gas development can play a transitional role, particularly for domestic use.
On the other hand, the energy transition has dramatically altered the risks. Global demand uncertainty means new oil and gas projects risk becoming stranded assets. Financing is shrinking, with many development banks and private lenders exiting fossil fuels. Also, opportunity costs are rising; every dollar locked into long-lived fossil infrastructure is a dollar not invested in renewables, grids, storage or clean industry.
Crucially, development today is no longer just about exporting fuels. It is about building resilient, diversified economies. Countries such as Morocco and Kenya show that renewable energy, green industry and regional power trade can support growth without deepening fossil dependence.
So, the question is no longer whether African countries can develop new oil and gas projects, but whether doing so supports long-term development, domestic energy access and fiscal stability in a transitioning world – or whether it risks locking countries into an extractive model that benefits few and exposes countries to future shocks.
CB: What is the hardest truth about Africa’s energy transition that policymakers and international partners are still unwilling to confront?
IA: For me, the hardest truth is this: Africa cannot deliver a just energy transition on unfair global terms. Despite all the rhetoric, global rules still limit Africa’s policy space. Trade and investment agreements restrict local content, industrial policy and value-addition strategies. Climate finance remains fragmented and insufficient. And mineral supply chains are governed largely by consumer-country priorities, not producer-country development needs.
Another uncomfortable truth is that not every “green” investment is automatically just. Without strong safeguards, renewable energy projects and mineral extraction can repeat the same harms as fossil fuels: displacement, exclusion and environmental damage.
Finally, there is a reluctance to admit that speed alone is not success. A rushed transition that ignores governance, equity and institutions will fail politically and socially, and, ultimately, undermine climate goals.
If Africa’s transition is to succeed, international partners must accept African leadership, African priorities and African definitions of development, even when that challenges existing power dynamics in global energy and mineral markets.
Watch, read, listen
CRISIS INFLAMED: In the Brazilian newspaper Folha de São Paulo, columnist Marcelo Leite looked into the climate impact of extracting more oil from Venezuela.
BEYOND TALK: Two Harvard scholars argued in Climate Home News for COP presidencies to focus less on climate policy and more on global politics.
EU LEVIES: A video explainer from the Hindu unpacked what the EU’s carbon border tax means for India and global trade.
Coming up
- 10-12 January: 16th session of the IRENA Assembly, Abu Dhabi
- 13-15 January: Energy Security and Green Infrastructure Week, London
- 13-15 January: The World Future Energy Summit, Abu Dhabi
- 15 January: Uganda general elections
Pick of the jobs
- WRI Polsky Energy Center, global director | Salary: around £185,000. Location: Washington DC; the Hague, Netherlands; New Delhi, Mumbai, or Bengaluru, India; or London
- UK government Advanced Research and Invention Agency, strategic communications director – future proofing our climate and weather | Salary: £115,000. Location: London
- The Wildlife Trusts, head of climate and international policy | Salary: £50,000. Location: London
- Children’s Investment Fund Foundation, senior manager for climate | Salary: Unknown. Location: London, UK
DeBriefed is edited by Daisy Dunne. Please send any tips or feedback to debriefed@carbonbrief.org.
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The post DeBriefed 9 January 2026: US to exit global climate treaty; Venezuelan oil ‘uncertainty’; ‘Hardest truth’ for Africa’s energy transition appeared first on Carbon Brief.
When people discuss climate change, most envision melting glaciers, smoke-filled skies from wildfires, or hurricanes ravaging coastlines. However, another crisis is unfolding in Canada’s North, one that is quieter but just as perilous: the melting of permafrost.
Permafrost is ground that has remained frozen for at least two years, though in many places, it has been frozen for thousands of years. It is a mix of soil, rock, and ice, and it covers almost half of Canada’s landmass, particularly in the Arctic. Think of it like the Earth’s natural deep freezer. Inside it are ancient plants, animal remains, and vast amounts of carbon that have been trapped and locked away for millennia.
As long as the permafrost stays frozen, those gases remain contained. But now, as temperatures rise and the Arctic warms nearly four times faster than the global average, that freezer door is swinging wide open.
Why the Arctic Matters to Everyone
It might be tempting to think of the Arctic as far away, remote, untouched, or disconnected from daily life in southern Canada. But the reality is that what happens in the Arctic affects everyone. Permafrost contains almost twice as much carbon as is currently in the Earth’s atmosphere. When it melts, that carbon escapes in the form of carbon dioxide and methane, two of the most potent greenhouse gases.
This creates a dangerous cycle: warmer air melts permafrost, which releases greenhouse gases, and those gases in turn contribute to even greater warming of the Earth. Scientists refer to this as a “feedback loop.” If large amounts of permafrost thaw, the gases released could overwhelm even the strongest climate policies, making it almost impossible to slow global warming.
The ripple effects are already visible. Melting permafrost worsens heatwaves in Ontario, intensifies wildfires in Alberta and British Columbia, and fuels stronger Atlantic storms. Rising global temperatures also bring increased insurance premiums, higher food prices, and strained infrastructure due to new climate extremes. The Arctic may be far north, but it is the beating heart of global climate stability.
Impacts Close to Home in Canada
For northern communities, the impacts of melting permafrost are immediate and deeply personal. Buildings, schools, and homes that were once stable on frozen foundations are cracking and sinking. Road’s twist and buckle, airstrips become unsafe, and pipelines leak as the ground beneath them shifts. This is not just inconvenient; it is life-threatening, as these systems provide access to food, medical care, and basic supplies in places already cut off from southern infrastructure.
The hamlet of Tuktoyaktuk, Northwest Territories, sits on the edge of the Arctic Ocean. As the permafrost beneath it thaws, the coastline is collapsing at an alarming rate of several meters each year. Entire homes have already been moved inland, and Elders warn that parts of the community may disappear into the sea within a generation. For residents, this is not just about losing land but losing ancestral ties to a place that has always been home.
In Inuvik, Northwest Territories, traditional underground ice cellars, once reliable food storage systems for generations, are collapsing into the permafrost. Families now face soaring costs to ship in groceries; undermining food security and cultural practices tied to country food.
Even the transportation routes that connect the North to the South are threatened. In the Yukon, the Dempster Highway, Canada’s only all-season road to the Arctic coast, is buckling as thawing permafrost destabilizes its foundation. Engineers are racing to repair roads that were never designed for melting ground, costing governments tens of millions of dollars each year.
And the South is not spared. The carbon released from permafrost melt contributes to the greenhouse gases driving climate extremes across Canada, including hotter summers in Toronto, devastating wildfires in Kelowna, severe flooding along the St. Lawrence, and worsening droughts on the Prairies. What melts in the North shapes life everywhere else.
Why Permafrost is Sacred in Indigenous Worldviews
For Indigenous Peoples of the Arctic, permafrost is not just frozen soil; it is a living part of their homeland and identity. Inuit, First Nations, and Métis Peoples have lived in relationship with frozen ground for thousands of years. The permafrost preserves sacred sites, traditional travel routes, and hunting lands. It has long been a source of stability, shaping the balance of ecosystems and making possible the cultural practices that sustain communities.
For Inuit in particular, permafrost has always been a trusted partner in food security. Ice cellars dug into the ground kept caribou, seal, fish, and whale meat fresh throughout the year. This practice is not only efficient and sustainable but also deeply cultural, tying families to cycles of harvest and sharing. As the permafrost melts and these cellars collapse, Inuit food systems are being disrupted. Families must rely more heavily on expensive store-bought food, which undermines both health and cultural sovereignty.
The thaw also threatens sacred spaces. Burial grounds are being disturbed, rivers and lakes are shifting, and the plants and animals that communities depend on are disappearing. In Indigenous worldviews, the land is kin alive and relational. When the permafrost melts, it signals not just an environmental crisis but a breaking of relationships that have been nurtured since time immemorial.
The Human Face of Melting Permafrost
The impacts of permafrost melt cannot be measured solely in terms of carbon emissions or financial costs. They must also be seen in the daily lives of the people who call the North home. In some communities, houses tilt and become uninhabitable, forcing residents to relocate, which disrupts family life, education, and mental health. In others, health centres and schools need constant repair, straining already limited budgets.
Travel across the land, once a predictable and safe experience, is now risky. Snowmobiles break through thinning ice. Trails flood or erode unexpectedly. Hunters face danger simply by trying to continue practices that have sustained their people for millennia.
For many Indigenous families, this is not only about the loss of infrastructure but also the loss of identity. When permafrost thaws, so do the practices tied to it: storing food, travelling safely, caring for burial sites, and teaching youth how to live in balance with the land. These changes erode culture, language, and ways of knowing that are inseparable from place.
Why the World Should Pay Attention
The melting of permafrost is not just a northern problem it is a global alarm bell. Scientists estimate that if even a fraction of the carbon stored in permafrost is released, it could equal the emissions from decades of current human activities. This is enough to derail international climate targets and lock the planet into a state of runaway warming.
This matters for everyone. Rising seas will not stop at Canada’s borders; they will flood coastal cities around the globe. Droughts and crop failures will disrupt food supplies and drive-up prices worldwide. Heatwaves will claim more lives in cities already struggling to keep cool. Economic costs will skyrocket, from insurance payouts to rebuilding disaster-hit communities. If the permafrost continues to thaw unchecked, the climate shocks of the past decade will look mild compared to what lies ahead.
But beyond the science, there is also a moral responsibility. The Arctic has contributed the least to climate change yet is suffering some of its most significant impacts. Indigenous communities, which have lived sustainably for generations, are now bearing the brunt of global emissions. For the world to ignore this crisis is to accept an injustice that will echo through history.
The Arctic is often referred to as the “canary in the coal mine” for climate change, but it is more than a warning system; it is a driver of global stability. If we lose the permafrost, we risk losing the fight against climate change altogether. Paying attention to what is happening in the Arctic is not optional. It is a test of whether humanity can listen, learn, and act before it is too late.
Moving Forward: Responsibility and Action
Addressing permafrost melt means tackling climate change at its root: cutting greenhouse gas emissions and transitioning to renewable energy. Canada must lead in reducing its dependence on oil and gas while investing in clean energy and climate-resilient infrastructure. But technical fixes alone are not enough. Indigenous-led monitoring, adaptation, and governance must be supported and prioritized.
In Nunavut and the Northwest Territories, Indigenous guardians and community researchers are already combining traditional knowledge with Western science to track permafrost thaw, monitor wildlife, and pilot new forms of housing built for unstable ground. These projects demonstrate that solutions are most effective when they originate from the individuals most closely connected to the land.
For families in southern Canada, the issue may seem distant. However, the truth is that every decision matters. The energy we use, the food we waste, and the products we buy all contribute to the warming that melts permafrost. By reducing consumption, supporting Indigenous-led initiatives, and advocating for robust climate policies, households far from the Arctic can still play a role in protecting it.
The permafrost is melting. It is reshaping the Arctic, altering Canada, and posing a threat to global climate stability. However, it also offers us a choice: to continue down a path of denial, or to act guided by science, led by Indigenous knowledge, and rooted in care for the generations to come.
Blog by Rye Karonhiowanen Barberstock
Image Credit : Alin Gavriliuc, Unsplash
The post Melting Ground: Why Permafrost Matters for Climate Change and Indigenous Peoples appeared first on Indigenous Climate Hub.
Melting Ground: Why Permafrost Matters for Climate Change and Indigenous Peoples
The Trump administration in the US has announced its intention to withdraw from the UN’s landmark climate treaty, alongside 65 other international bodies that “no longer serve American interests”.
Every nation in the world has committed to tackling “dangerous anthropogenic interference with the climate system” under the 1992 UN Framework Convention on Climate Change (UNFCCC).
During Donald Trump’s second presidency, the US has already failed to meet a number of its UN climate treaty obligations, including reporting its emissions and funding the UNFCCC – and it has not attended recent climate summits.
However, pulling out of the UNFCCC would be an unprecedented step and would mark the latest move by the US to disavow global cooperation and climate action.
Among the other organisations the US plans to leave is the Intergovernmental Panel on Climate Change (IPCC), the UN body seen as the global authority on climate science.
In this article, Carbon Brief considers the implications of the US leaving these bodies, as well as the potential for it rejoining the UNFCCC in the future.
Carbon Brief has also spoken to experts about the contested legality of leaving the UNFCCC and what practical changes – if any – will result from the US departure.
- What is the process for pulling out of the UNFCCC?
- Is it legal for Trump to take the US out of the UNFCCC unilaterally?
- How could the US rejoin the UNFCCC and Paris Agreement?
- What changes when the US withdraws from the UNFCCC?
- What about the US withdrawal from the IPCC?
- What other organisations are affected?
What is the process for pulling out of the UNFCCC?
The Trump administration set out its intention to withdraw from the UNFCCC and the IPCC in a White House presidential memorandum issued on 7 January 2026.
It claims authority “vested in me as president by the constitution and laws of the US” to withdraw the country from the treaty, along with 65 other international and UN bodies.
However, the memo includes a caveat around its instructions, stating:
“For UN entities, withdrawal means ceasing participation in or funding to those entities to the extent permitted by law.”
(In an 8 January interview with the New York Times, Trump said he did not “need international law” and that his powers were constrained only by his “own morality”.)
The US is the first and only country in the world to announce it wants to withdraw from the UNFCCC.
The convention was adopted at the UN headquarters in New York in May 1992 and opened for signatures at the Rio Earth summit the following month. The US became the first industrialised nation to ratify the treaty that same year.
It was ultimately signed by every nation on Earth – making it one of the most ratified global treaties in history.
Article 25 of the treaty states that any party may withdraw by giving written notification to the “depositary”, which is elsewhere defined as being the UN secretary general – currently, António Guterres.
The article, shown below, adds that the withdrawal will come into force a year after a written notification is supplied.
The treaty adds that any party that withdraws from the convention shall be considered as also having left any related protocol.
The UNFCCC has two main protocols: the Kyoto Protocol of 1997 and the Paris Agreement of 2015.
Although former US president Bill Clinton signed the Kyoto Protocol in 1998, its formal ratification faced opposition from the Senate and the treaty was ultimately rejected by his successor, president George W Bush, in 2001.
Domestic opposition to the protocol centred around the exclusion of major developing countries, such as China and India, from emissions reduction measures.
The US did ratify the Paris Agreement, but Trump signed an executive order to take the nation out of the pact for a second time on his first resumed day in office in January 2025.
Is it legal for Trump to take the US out of the UNFCCC unilaterally?
Whether Trump can legally pull the US out of the UNFCCC without the consent of the Senate remains unclear.
The US previously left the Paris Agreement during Trump’s first term.
Both the UNFCCC and the Paris Agreement allow any party to withdraw with a year’s written notice. However, both treaties state that parties cannot withdraw within the first three years of ratification.
As such, the first Trump administration filed notice to exit the Paris Agreement in November 2019 and became the first nation in the world to formally leave a year later – the day after Democrat Joe Biden won the 2020 presidential election.
On his first day in office in 2021, Biden rejoined the Paris Agreement. This took 30 days from notifying the UNFCCC to come into force.
The legalities of leaving the UNFCCC are murkier, due to how it was adopted.
As Michael B Gerrard, director of the Sabin Center for Climate Change Law at Columbia Law School, explains to Carbon Brief, the Paris Agreement was ratified without Senate approval.
Article 2 of the US Constitution says presidents have the power to make or join treaties subject to the “advice and consent” of the Senate – including a two-thirds majority vote (see below).
However, Barack Obama took the position that, as the Paris Agreement “did not impose binding legal obligations on the US, it was not a treaty that required Senate ratification”, Gerrard tells Carbon Brief.
As noted in a post by Jake Schmidt, a senior strategic director at the environmental NGO Natural Resources Defense Council (NRDC), the US has other mechanisms for entering international agreements. It says the US has joined more than 90% of the international agreements it is party to through different mechanisms.
In contrast, George H Bush did submit the UNFCCC to the Senate in 1992, where it was unanimously ratified by a 92-0 vote, ahead of his signing it into law.
Reversing this is uncertain legal territory. Gerrard tells Carbon Brief:
“There is an open legal question whether a president can unilaterally withdraw the US from a Senate-ratified treaty. A case raising that question reached the US Supreme Court in 1979 (Goldwater vs Carter), but the Supreme Court ruled this was a political question not suitable for the courts.”
Unlike ratifying a treaty, the US Constitution does not explicitly specify whether the consent of the Senate is required to leave one.
This has created legal uncertainty around the process.
Given the lack of clarity on the legal precedent, some have suggested that, in practice, Trump can pull the US out of treaties unilaterally.
Sue Biniaz, former US principal deputy special envoy for climate and a key legal architect of the Paris Agreement, tells Carbon Brief:
“In terms of domestic law, while the Supreme Court has not spoken to this issue (it treated the issue as non-justifiable in the Goldwater v Carter case), it has been US practice, and the mainstream legal view, that the president may constitutionally withdraw unilaterally from a treaty, ie without going back to the Senate.”
Additionally, the potential for Congress to block the withdrawal from the UNFCCC and other treaties is unclear. When asked by Carbon Brief if it could play a role, Biniaz says:
“Theoretically, but politically unlikely, Congress could pass a law prohibiting the president from unilaterally withdrawing from the UNFCCC. (The 2024 NDAA contains such a provision with respect to NATO.) In such case, its constitutionality would likely be the subject of debate.”
How could the US rejoin the UNFCCC and Paris Agreement?
The US would be able to rejoin the UNFCCC in future, but experts disagree on how straightforward the process would be and whether it would require a political vote.
In addition to it being unclear whether a two-thirds “supermajority” vote in the Senate is required to leave a treaty, it is unclear whether rejoining would require a similar vote again – or if the original 1992 Senate consent would still hold.
Citing arguments set out by Prof Jean Galbraith of the University of Pennsylvania law school, Schmidt’s NRDC post says that a future president could rejoin the convention within 90 days of a formal decision, under the merit of the previous Senate approval.
Biniaz tells Carbon Brief that there are “multiple future pathways to rejoining”, adding:
“For example, Prof Jean Galbraith has persuasively laid out the view that the original Senate resolution of advice and consent with respect to the UNFCCC continues in effect and provides the legal authority for a future president to rejoin. Of course, the Senate could also give its advice and consent again. In any case, per Article 23 of the UNFCCC, it would enter into force for the US 90 days after the deposit of its instrument.”
Prof Oona Hathaway, an international law professor at Yale Law School, believes there is a “very strong case that a future president could rejoin the treaty without another Senate vote”.
She tells Carbon Brief that there is precedent for this based on US leaders quitting and rejoining global organisations in the past, explaining:
“The US joined the International Labour Organization in 1934. In 1975, the Ford administration unilaterally withdrew, and in 1980, the Carter administration rejoined without seeking congressional approval.
“Similarly, the US became a member of the United Nations Educational, Scientific and Cultural Organization (UNESCO) in 1946. In the 1980s, the Reagan administration unilaterally withdrew the US. The Bush administration rejoined UNESCO in 2002, but in 2019 the Trump administration once again withdrew. The Biden administration rejoined in 2023, and the Trump Administration announced its withdrawal again in 2025.”
But this “legal theory” of a future US president specifically re-entering the UNFCCC “based on the prior Senate ratification” has “never been tested in court”, Prof Gerrard from Columbia Law School tells Carbon Brief.
Dr Joanna Depledge, an expert on global climate negotiations and research fellow at the University of Cambridge, tells Carbon Brief:
“Due to the need for Senate ratification of the UNFCCC (in my interpretation), there is no way back now for the US into the climate treaties. But there is nothing to stop a future US president applying [the treaty] rules or – what is more important – adopting aggressive climate policy independently of them.”
If it were required, achieving Senate approval to rejoin the UNFCCC would take a “significant shift in US domestic politics”, public policy professor Thomas Hale from the University of Oxford notes on Bluesky.
Rejoining the Paris Agreement, on the other hand, is a simpler process that the US has already undertaken in recent years. (See: Is it legal for Trump to take the US out of the UNFCCC unilaterally?) Biniaz explains:
“In terms of the Paris Agreement, a party to that agreement must also be a party to the UNFCCC (Article 20). Assuming the US had rejoined the UNFCCC, it could rejoin the Paris Agreement as an executive agreement (as it did in early 2021). The agreement would enter into force for the US 30 days after the deposit of its instrument (Article 21).”
The Center for Climate and Energy Solutions, an environmental non-profit, explains that Senate approval was not required for Paris “because it elaborates an existing treaty” – the UNFCCC.
What changes when the US withdraws from the UNFCCC?
US withdrawal from the UNFCCC has been described in media coverage as a “massive hit” to global climate efforts that will “significantly limit” the treaty’s influence.
However, experts tell Carbon Brief that, as the Trump administration has already effectively withdrawn from most international climate activities, this latest move will make little difference.
Moreover, Depledge tells Carbon Brief that the international climate regime “will not collapse” as a result of US withdrawal. She says:
“International climate cooperation will not collapse because the UNFCCC has 195 members rather than 196. In a way, the climate treaties have already done their job. The world is already well advanced on the path to a lower-carbon future. Had the US left 10 years ago, it would have been a serious threat, but not today. China and other renewable energy giants will assert even more dominance.”
Depledge adds that while the “path to net-zero will be longer because of the drastic rollback of domestic climate policy in the US”, it “won’t be reversed”.
Technically, US departure from the UNFCCC would formally release it from certain obligations, including the need to report national emissions.
As the world’s second-largest annual emitter, this is potentially significant.
“The US withdrawal from the UNFCCC undoubtedly impacts on efforts to monitor and report global greenhouse gas emissions,” Dr William Lamb, a senior researcher at the Potsdam Institute for Climate Impact Research (PIK), tells Carbon Brief.
Lamb notes that while scientific bodies, such as the IPCC, often use third-party data, national inventories are still important. The US already failed to report its emissions data last year, in breach of its UNFCCC treaty obligations.
Robbie Andrew, senior researcher at Norwegian climate institute CICERO, says that it will currently be possible for third-party groups to “get pretty close” to the carbon dioxide (CO2) emissions estimates previously published by the US administration. However, he adds:
“The further question, though, is whether the EIA [US Energy Information Administration] will continue reporting all of the energy data they currently do. Will the White House decide that reporting flaring is woke? That even reporting coal consumption is an unnecessary burden on business? I suspect the energy sector would be extremely unhappy with changes to the EIA’s reporting, but there’s nothing at the moment that could guarantee anything at all in that regard.”
Andrew says that estimating CO2 emissions from energy is “relatively straightforward when you have detailed energy data”. In contrast, estimating CO2 emissions from agriculture, land use, land-use change and forestry, as well as other greenhouse gas emissions, is “far more difficult”.
The US Treasury has also announced that the US will withdraw from the UN’s Green Climate Fund (GCF) and give up its seat on the board, “in alignment” with its departure from the UNFCCC. The Trump administration had already cancelled $4bn of pledged funds for the GCF.
Another specific impact of US departure would be on the UNFCCC secretariat budget, which already faces a significant funding gap. US annual contributions typically make up around 22% of the body’s core budget, which comes from member states.
However, as with emissions data and GCF withdrawal, the Trump administration had previously indicated that the US would stop funding the UNFCCC.
In fact, billionaire and UN special climate envoy Michael Bloomberg has already committed, alongside other philanthropists, to making up the US shortfall.
Veteran French climate negotiator Paul Watkinson tells Carbon Brief:
“In some ways the US has already suspended its participation. It has already stopped paying its budget contributions, it sent no delegation to meetings in 2025. It is not going to do any reporting any longer – although most of that is now under the Paris Agreement. So whether it formally leaves the UNFCCC or not does not change what it is likely to do.”
Dr Joanna Depledge tells Carbon Brief that she agrees:
“This is symbolically and politically huge, but in practice it makes little difference, given that Trump had already announced total disengagement last year.”
The US has a history of either leaving or not joining major environmental treaties and organisations, such as the Paris Agreement and the Kyoto Protocol. (See: What is the process for pulling out of the UNFCCC?)
Dr Jennifer Allan, a global environmental politics researcher at Cardiff University, tells Carbon Brief:
“The US has always been an unreliable partner…Historically speaking, this is kind of more of the same.”
The NRDC’s Jake Schmidt tells Carbon Brief that he doubts US absence will lead to less progress at UN climate negotiations. He adds:
“[The] Trump team would have only messed things up, so not having them participate will probably actually lead to better outcomes.”
However, he acknowledges that “US non-participation over the long-term could be used by climate slow-walking countries as an excuse for inaction”.
Biniaz tells Carbon Brief that the absence of the US is unlikely to unlock reform of the UN climate process – and that it might make negotiations more difficult. She says:
“I don’t see the absence of the US as promoting reform of the COP process. While the US may have had strong views on certain topics, many other parties did as well, and there is unlikely to be agreement among them to move away from the consensus (or near consensus) decision-making process that currently prevails. In fact, the US has historically played quite a significant ‘broker’ role in the negotiations, which might actually make it more difficult for the remaining parties to reach agreement.”
After leaving the UNFCCC, the US would still be able to participate in UN climate talks as an observer, albeit with diminished influence. (It is worth noting that the US did not send a delegation to COP30 last year.)
There is still scope for the US to use its global power and influence to disrupt international climate processes from the outside.
For example, last year, the Trump administration threatened nations and negotiators with tariffs and withdrawn visa rights if they backed an International Maritime Organization (IMO) effort to cut shipping emissions. Ultimately, the measures were delayed due to a lack of consensus.
(Notably, the IMO is among the international bodies that the US has not pledged to leave.)
What about the US withdrawal from the IPCC?
As a scientific body, rather than a treaty, there is no formal mechanism for “withdrawing” from the IPCC. In its own words, the IPCC is an “organisation of governments that are members of the UN or World Meteorological Organization” (WMO).
Therefore, just being part of the UN or WMO means a country is eligible to participate in the IPCC. If a country no longer wishes to play a role in the IPCC, it can simply disengage from its activities – for example, by not attending plenary meetings, nominating authors or providing financial support.
This is exactly what the US government has been doing since last year.
Shortly before the IPCC’s plenary meeting for member governments – known as a “session” – in Hangzhou, China, in March 2025, reports emerged that US officials had been denied permission to attend.
In addition, the contract for the technical support unit for Working Group III (WG3) was terminated by its provider, NASA, which also eliminated the role of chief scientist – the position held by WG3 co-chair Dr Kate Cavlin.
(Each of the IPCC’s three “working groups” has a technical support unit, or TSU, which provides scientific and operational support. These are typically “co-located” between the home countries of a working group’s two co-chairs.)
The Hangzhou session was the first time that the US had missed a plenary since the IPCC was founded in 1988. It then missed another in Lima, Peru, in October 2025.
Although the US government did not nominate any authors for the IPCC’s seventh assessment cycle (AR7), US scientists were still put forward through other channels. Analysis by Carbon Brief shows that, across the three AR7 working group reports, 55 authors are affiliated with US institutions.
However, while IPCC authors are supported by their institutions – they are volunteers and so are not paid by the IPCC – their travel costs for meetings are typically covered by their country’s government. (For scientists from developing countries, there is financial support centrally from the IPCC.)
Prof Chris Field, co-chair of Working Group II during the IPCC’s fifth assessment (AR5), tells Carbon Brief that a “number of philanthropies have stepped up to facilitate participation by US authors not supported by the US government”.
The US Academic Alliance for the IPCC – a collaboration of US universities and research institutions formed last year to fill the gap left by the government – has been raising funds to support travel.
In a statement reacting to the US withdrawal, IPCC chair Prof Sir Jim Skea said that the panel’s focus remains on preparing the reports for AR7:
“The panel continues to make decisions by consensus among its member governments at its regular plenary sessions. Our attention remains firmly on the delivery of these reports.”
The various reports will be finalised, reviewed and approved in the coming years – a process that can continue without the US. As it stands, the US government will not have a say on the content and wording of these reports.
Field describes the US withdrawal as a “self-inflicted wound to US prestige and leadership” on climate change. He adds:
“I don’t have a crystal ball, but I hope that the US administration’s animosity toward climate change science will lead other countries to support the IPCC even more strongly. The IPCC is a global treasure.”
The University of Edinburgh’s Prof Gabi Hegerl, who has been involved in multiple IPCC reports, tells Carbon Brief:
“The contribution and influence of US scientists is presently reduced, but there are still a lot of enthusiastic scientists out there that contribute in any way they can even against difficult obstacles.”
On Twitter, Prof Jean-Pascal van Ypersele – IPCC vice-chair during AR5 – wrote that the US withdrawal was “deeply regrettable” and that to claim the IPCC’s work is contrary to US interests is “simply nonsensical”. He continued:
“Let us remember that the creation of the IPCC was facilitated in 1988 by an agreement between Ronald Reagan and Margaret Thatcher, who can hardly be described as ‘woke’. Climate and the environment are not a matter of ideology or political affiliation: they concern everyone.”
Van Ypersele added that while the IPCC will “continue its work in the service of all”, other countries “will have to compensate for the budgetary losses”.
The IPCC’s most recent budget figures show that the US did not make a contribution in 2025.
Carbon Brief analysis shows that the US has provided around 30% of all voluntary contributions in the IPCC’s history. Totalling approximately $67m (£50m), this is more than four times that of the next-largest direct contributor, the EU.
However, this is not the first time that the US has withdrawn funding from the IPCC. During Trump’s first term of office, his administration cut its contributions in 2017, with other countries stepping up their funding in response. The US subsequently resumed its contributions.
At its most recent meeting in Lima, Peru, in October 2025, the IPCC warned of an “accelerating decline” in the level of annual voluntary contributions from countries and other organisations, reported the Earth Negotiations Bulletin. As a result, the IPCC invited member countries to increase their donations “if possible”.
What other organisations are affected?
In addition to announcing his plan to withdraw the US from the UNFCCC and the IPCC, Trump also called for the nation’s departure from 16 other organisations related to climate change, biodiversity and clean energy.
These include:
- The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) – the biodiversity equivalent of the IPCC.
- Intergovernmental Forum on Mining, Minerals, Metals and Sustainable Development – a voluntary group of more than 80 countries aiming to make the mining sector more sustainable.
- UN Energy – the principal UN organisation for international collaboration on energy.
- UN Oceans – a UN mechanism responsible for overseeing the International Seabed Authority (ISA) and other UN agencies related to ocean and coastal issues.
- UN Water – the UN agency responsible for water and sanitation.
- UN Collaborative Programme on Reducing Emissions from Deforestation and Forest Degradation in Developing Countries (UN-REDD) – a UN collaborative initiative for creating financial incentives for protecting forests.
- International Renewable Energy Agency – an intergovernmental organisation supporting countries in their transition to renewable energy.
- 24/7 Carbon-Free Energy Compact – a UN initiative launched in 2021 pushing governments, companies and organisations to achieve 100% low-carbon electricity generation.
- Commission for Environmental Cooperation – an organisation aimed at conserving North America’s natural environment.
- Inter-American Institute for Global Change Research – an intergovernmental organisation supported by 19 countries in North and South America for the support of planetary change research.
- International Energy Forum – an intergovernmental platform for dialogue among countries, industry and experts.
- International Solar Alliance – an organisation supporting the development of solar power and the phaseout of fossil fuels.
- International Tropical Timber Organization – an organisation aimed at protecting tropical forest resources.
- International Union for Conservation of Nature – an international nature conservation organisation and authority on the state of biodiversity loss.
- Renewable Energy Policy Network for the 21st Century – a global policy forum for renewable energy leadership.
- Secretariat of the Pacific Regional Environment Programme – a regional organisation aimed at protecting the Pacific’s environment.
As well as participating in the work of these organisations, the US is also a key source of funding for many of them – leaving their futures uncertain.
In a letter to members seen by Carbon Brief, IPBES chair and Kenyan ecologist, Dr David Obura, described Trump’s move as “deeply disappointing”.
He said that IPBES “has not yet received any formal notification” from the US, but “anticipates that the intention expressed to withdraw will mean that the US will soon cease to be a member of IPBES”, adding:
“The US is a founding member of IPBES and scientists, policymakers and stakeholders – including Indigenous peoples and local communities – from the US have been among the most engaged contributors to the work of IPBES since its establishment in 2012, making valuable contributions to objective science-based assessments of the state of the planet, for people and nature.
“The contribution of US experts ranges from leading landmark assessment reports, to presiding over negotiations, serving as authors and reviewers, as well as helping to steer the organisation both scientifically and administratively.”
Despite being a party to IPBES until now, the US has never been a signatory to the UN Convention on Biological Diversity (CBD), the nature equivalent of the UNFCCC.
It is one of only two nations not to sign the convention, with the other being the Holy See, representing the Vatican City.
The lack of US representation at the CBD has not prevented countries from reaching agreements. In 2022, countries gathered under the CBD adopted the Kunming-Montreal Global Biodiversity Framework, often described as the “Paris Agreement for nature”.
However, some observers have pointed to the lack of US involvement as one of the reasons why biodiversity loss has received less international attention than climate change.
The post Q&A: What Trump’s US exit from UNFCCC and IPCC could mean for climate action appeared first on Carbon Brief.
Q&A: What Trump’s US exit from UNFCCC and IPCC could mean for climate action
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