The past three years have been exceptionally warm globally.
In 2023, global temperatures reached a new high, after they significantly exceeded expectations.
This record was surpassed in 2024 – the first year where average global temperatures were 1.5C above pre-industrial levels.
Now, 2025 is on track to be the second- or third-warmest year on record.
What has caused this apparent acceleration in warming has been subject to a lot of attention in both the media and the scientific community.
Dozens of papers have been published investigating the different factors that could have contributed to these record temperatures.
In 2024, the World Meteorological Organization (WMO) discussed potential drivers for the warmth in a special section of its “state of the global climate” report, while the American Geophysical Union ran a session on the topic at its annual meeting.
In this article, Carbon Brief explores four different factors that have been proposed for the exceptional warmth seen in recent years. These are:
- A strong El Niño event that developed in the latter part of 2023.
- Rapid declines in sulphur dioxide emissions – particularly from international shipping and China.
- An unusual volcanic eruption in Tonga in 2022.
- A stronger-than-expected solar cycle.
Carbon Brief’s analysis finds that a combination of these factors explains most of the unusual warmth observed in 2024 and half of the difference between observed and expected warming in 2023.
However, natural fluctuations in the Earth’s climate may have also played a role in the exceptional temperatures, alongside signs of declining cloud cover that may have implications for the sensitivity of the climate to human-caused emissions.
An unusually warm three years
Between 1970 and 2014, average surface temperatures rose at a fairly steady rate of around 0.18C per decade.
Set against this long-term trend, temperature increases during the period from 2015 to 2022 were on the upper end of what would be expected.
The increases seen in 2023, 2024 and 2025 were well outside of that range.
The high temperatures of the past three years reflect a broader acceleration in the rate of warming over the past decade.
However, the past three years were unusually warm, even when compared to other years in the 2010s and 2020s.
Record-breaking warmth in 2023 meant that it beat the prior warmest year of 2016 by 0.17C – the largest magnitude of a new record in the past 140 years.
The year 2024 then swiftly broke 2023’s record, becoming the first year where average global temperatures exceeded 1.5C above pre-industrial levels.
The 10 months of data available for 2025 indicates that the year is likely to be slightly cooler than 2023 – though it is possible it may tie or be slightly warmer.
The figure below shows global surface temperatures between 1970 and 2025. (The figures for 2025 include uncertainty based on the remaining three months of the year.)
It includes a smoothed average based on temperature data for 1970-2022 that takes into account some acceleration of warming – and then extrapolates that smoothed average forward to 2023-25 to determine what the expected temperature for those years would have been. (This follows the approach used in the WMO’s “state of the global climate 2024” report.)
This approach calculates how much warmer the past three years were than would be expected given the long-term trend in temperatures.
It shows that 2023 was around 0.18C warmer than expected, 2024 was a massive 0.25C warmer and 2025 is likely to be 0.11C warmer.
Researchers have identified a number of potential drivers of unexpected warmth over 2023-25. Here, Carbon Brief looks at the evidence for each one.
A weirdly behaving El Niño event
El Niño is a climate pattern of unusually warm sea surface temperatures (SSTs) in the tropical Pacific that naturally occurs every two to seven years. Strong El Niño years generally have warmer global temperatures, with the largest effect generally occurring in the months after El Niño conditions peak (when SSTs reach their highest levels in the tropical Pacific).
A relatively strong El Niño event developed in the latter half of 2023, peaking around November before fading in the spring of 2024.
This event was the fourth-strongest El Niño ever recorded, as measured according to SSTs in the Niño 3.4 region in the central tropical Pacific. However, it was notably weaker than the El Niño events in both 1998 and 2016.
This can be seen in the chart below, which shows the strength of El Niño events (red shading) since the 1980s. (The blue shading indicates La Niña events – the opposite part of the cycle to El Niño, which results in cooler SSTs in the tropical Pacific.)
(It is worth noting that measuring the strength of El Niño events is not entirely straightforward. Other tools used by scientists to monitor changes to El Niño – such as the US National Oceanic and Atmospheric Administration’s (NOAA’s) multivariate ENSO index – show the 2023-24 event was much weaker than indicated in the Niño 3.4 dataset.)
Global surface air temperatures tend to be elevated by around 0.1-0.2C in the six months after the peak of a strong El Niño event – defined here as when SSTs in the Niño 3.4 region reach 1.5C above normal.
The figure below shows the range of global temperature change for the 12 months before and 22 months after the peak of all 10 strong El Niño events since 1950. The light line represents the average of past strong El Niño events, the dark blue line the temperature change observed during the 2023-24 event and the shaded blue area the 5-95th percentile range.
The figure shows the 2023-24 El Niño was quite unusual compared to other strong El Niño events since 1970. Global temperatures rose to around 0.4C above expected levels – which is on the high side of previous El Niños.
The heat also came early, with high temperatures showing up around four months before the El Niño event peaked. This early heat is unlike any other El Niño event in modern history and is one of the reasons why 2023’s global temperatures were so unexpectedly warm.
Global temperatures remained elevated for a full 18 months after the El Niño peaked, well after conditions in the tropical Pacific shifted into neutral conditions – and even after mild La Niña conditions developed at the end of 2024 and into early 2025.
This figure does not explain how much of this unusual heat was actually caused by El Niño, compared to other factors, but it does suggest that El Niño behaviour alone does not fully explain unusually high temperatures in recent years.
Based on the historical relationship between El Niño and global temperatures, Carbon Brief estimates that El Niño contributed a modest 0.013C to 2023 temperatures and a more substantial 0.128C to 2024 temperatures, albeit with large uncertainties. (See “methodology” section at the end for details.)
However, it is possible that this 2023 estimate is too low. There are some suggestions in the literature that 2023-24 El Niño’s early warmth may have been caused by the rapid transition out of a particularly extended La Niña event. There are indications that temperatures have spiked in similar situations further back in the historical temperature record.
Falling sulphur dioxide emissions
Sulphur dioxide (SO2) is an aerosol that is emitted into the lower atmosphere by the burning of coal and oil. It has a powerful climate cooling effect – Carbon Brief analysis shows that global emissions of SO2 have masked about one-third of historical warming.
Global SO2 emissions have declined around 40% over the past 18 years, as countries have increasingly prioritised reducing air pollution, including through the installation of scrubbers at coal plants.
These declines have been particularly concentrated in China, which has seen a 70% decline in SO2 emissions since 2007. In addition, a rule introduced for international shipping in 2020 by the International Maritime Organization (IMO) has resulted in an 80% decline in the sulphur content of shipping fuel used around the world.
The decline of SO2 emissions is shown in the figure below.
Shipping in particular has been suggested as a potential culprit for recent temperatures, given that ships emit SO2 over oceans where the air tends to be cleaner and so emissions have a bigger effect.
Seven of the eight studies that have explored the temperature impact of the IMO regulations have suggested a relatively modest effect, in the range of 0.03-0.08C. However, one study – led by former NASA scientist Dr James Hansen – calculated a much stronger effect of 0.2C that would explain virtually all the unusual warmth of recent years.
The figure below shows Carbon Brief’s estimate of the global average surface temperature changes caused by the low-sulphur shipping fuel rules, using the estimates produced by all eight studies. The central estimate (dark blue line) is relatively low, at around 0.05C, but the uncertainty range (light blue shading) across the studies remains large.
Overall, Carbon Brief’s analysis finds that around 0.04C of warming over 2020-23 and 0.05C of warming over 2020-24 can be attributed to SO2 declines from shipping and other sources.
However, this approach might slightly overstate the effects of SO2 on the exceptional temperatures of the past three years, as shipping and other SO2 declines would have had some effect on 2021 and 2022 as well.
It is also worth noting that the total effects of SO2 declines on global temperatures have been considerably larger and are estimated to be responsible for around one-quarter of all warming since 2007.
However, these SO2 decreases occurred over a long period of time and do not clearly explain the recent spike in temperatures.
An unusual volcanic eruption in Tonga
In early 2022, the Hunga Tonga-Hunga Ha’apai underwater volcano erupted spectacularly, sending a plume 55km into the atmosphere. This was by far the most explosive volcanic eruption since Mount Pinatubo erupted in 1991.
This was a highly unusual volcanic eruption, which vaporised vast amounts of sea water and lofted it high into the atmosphere. Overall, around 146m metric tonnes of water vapour ended up in the stratosphere, which is the layer of the atmosphere above the troposphere.
Water vapour is a powerful greenhouse gas. While it is short-lived in the lower atmosphere, it can stick around for years in the stratosphere, where it has a significant warming effect on the climate.
The figure below shows the concentration of water vapour in the stratosphere between 2005 and mid-2025. It shows how the 2022 eruption increased atmospheric concentrations of the greenhouse gas by around 15%. More than half the added water vapour has subsequently fallen out of the upper atmosphere.
Most early studies of the Hunga Tonga-Hunga Ha’apai volcano focused specifically on the effects of stratospheric water vapour. These tended to show strong warming in the lower stratosphere and cooling in the middle-to-upper stratosphere, but only a slight warming effect on global surface temperatures of around 0.05C.
Hunga Tonga-Hunga Ha’apai had much lower sulphur emissions than prior explosive eruptions, such as Pinatubo and El Chichon. However it put 0.5–1.5m tonnes of sulphur into the stratosphere – the most from an eruption since Pinatubo.
Studies that included both sulphur and water vapour effects tend to find that the net effect of the eruption on surface temperatures was slight global cooling, concentrated in the southern hemisphere.
By using the estimates published in a 2024 study published in Geophysical Research Letters, which used the FaIR climate emulator model, Carbon Brief estimates that the Hunga Tonga-Hunga Ha’apai eruption cooled global surface temperatures by -0.01C in 2023 and -0.02C in 2024.
This suggests that the eruption was likely only a minor contributor to recent global surface temperatures.
A stronger-than-expected solar cycle
The source of almost all energy on Earth is the sun. Over hundreds of millions of years, variations in solar output have a big impact on the global climate.
Thankfully, over shorter periods of time the sun is remarkably stable, helping keep the Earth’s climate habitable for life. (Big changes – such as ice ages – have more to do with variations in the Earth’s orbit than changes in solar output.)
However, slight changes in solar output do occur – and when they do, they can influence climate change over shorter periods of time. The most important of these is the roughly 11-year solar cycle, which is linked with the sun’s magnetic field and results in changes in the number of sunspots and amount of solar energy reaching Earth.
The figure below shows a best-estimate of changes in total solar irradiance since 1980, based on satellite observations. Total solar irradiance is a measure of the overall amount of solar energy that reaches the top of the Earth’s atmosphere and is measured in watts per metre squared.
The 11-year solar cycle is relatively modest compared to the sun’s total output, varying only a few watts per metre squared between peak and trough – amounting to around 0.01% of solar output. However, these changes can result in variations of up to 0.1C in global temperatures within a decade.
The most recent solar cycle – solar cycle 25 – began around 2020 and has been the strongest solar cycle measured since 1980. It was stronger than most models had anticipated and likely contributed to around 0.04C global warming in 2023 and 0.07C in 2024.
Putting together the drivers
By combining earlier estimates of different factors contributing to 2023 and 2024 global surface temperatures, about half of 2023’s unusual warmth and almost all of 2024’s unusual warmth can be effectively explained.
This is illustrated in the figure below, which shows the five different factors discussed earlier – El Niño, shipping SO2, Chinese SO2, the Hunga Tonga-Hunga Ha’apai volcano and solar cycle changes – along with their respective uncertainties.
The sum of all the factors is shown in the “combined” bar, while the actual warming compared to expectations is shown in red.
The upper chart shows 2023, while the lower one shows 2024.
It is important to note that the first bar includes both El Niño and natural year-to-year variability; the height of the bar reflects the best estimate of El Niño’s effects, while the uncertainty range encompasses year-to-year variability in global temperatures that may be – at least in part – unrelated to El Niño.
The role of natural climate variability
Large natural variability to the Earth’s climate is one of the main reasons why the combined value of the different drivers of expected warmth in 2023 has an uncertainty range that exceeds the observed warming – even though the best-estimate of combined factors only explains half of temperatures.
Or, to put it another way, there is up 0.15C difference in global temperatures year-on-year that cannot be explained solely by El Niño, human-driven global warming, or natural “forcings” – such as volcanoes or variations in solar output.
The figure below shows the difference between actual and expected warming in the global temperature record for every year in the form of a histogram. The vertical zero line represents the expectation given long-term global warming and the other vertical lines indicate the warming seen in 2023, 2024 and 2025.
The height of each blue bar represents the number of years over 1850-2024 when the average global temperature was that far (above or below) the expected level of warming.
Based on the range of year-to-year variability, temperatures would be expected to spike as far above the long-term trend as they did in 2023 once every 25 years, on average. The year 2024 would be a one-in-88 year event, whereas 2025 would be a less-unusual, one-in-seven year event.
These likelihoods for the past three years are sensitive to the approach used to determine what the longer-term warming level should be.
In this analysis, Carbon Brief used a local smoothing approach (known as locally estimated scatterplot smoothing) to determine the expected temperatures, following the approach used in the WMO “state of the climate 2024” report.
This approach results in a warming of 1.28C in 2023 and 1.30C in 2024, against which observed temperatures are compared.
Other published estimates put the longer-term warming in 2024 notably higher.
Earlier this year, the scientists behind the “Indicators of Global Climate Change” (IGCC) report estimated that human activity caused 1.36C of recent warming in 2024. They also found a slightly lower overall warming level for 2024 – 1.52C, as opposed to the WMO’s 1.55C – because they looked exclusively at datasets used by IPCC AR6. (This meant estimates from the Copernicus/ECMWF’s ERA5 dataset were not included.)
Based on climate simulations, the IGCC report finds the likelihood of 2024’s warmth to be a one-in-six year event and 2023’s a one-in-four event.
Using the same assumptions as the IGCC, Carbon Brief’s approach calculates that 2024 would be a less-common, one-in-18 year event.
However, the IGCC estimate of current human-induced warming is based on the latest estimates of human and natural factors warming the climate. That means that it already accounts for additional warming from low-sulphur shipping fuel, East Asian aerosols and other factors discussed above.
Therefore, the results from these two analyses are not necessarily inconsistent: natural climate variability (including El Niño) played a key role – but this came in addition to other factors. Natural fluctuations in the Earth’s climate alone would have been unlikely to result in the extreme global temperatures seen in 2023, 2024 and 2025.
A cloudy picture
Even if unusual recent global warmth can be mostly attributed to a combination of El Niño, falling SO2 emissions, the Hunga Tonga-Hunga Ha’apai volcano, solar cycle changes and natural climate variability, there are a number of questions that remain unanswered.
Most important is what the record warmth means for the climate going forward. Is it likely to revert to the long-term average warming level, or does it reflect an acceleration in the underlying rate of warming – and, if so, what might its causes be?
As explained by Carbon Brief in a 2023 article, climate models have suggested that warming will speed up. Some of this acceleration is built into the analysis presented here, which includes a slightly faster rate of warming in recent years than has characterised the period since 1970.
But there are broader questions about what – beyond declining SO2 and other aerosols – is driving this acceleration.
Research recently published in the journal Science offered some potential clues. It found a significant decline in planetary reflectivity – known as albedo – over the past decade, associated with a reduced low-level cloud cover that is unprecedented in the satellite record.
The authors suggest it could be due to a combination of three different factors: natural climate variability, changing SO2 and other aerosol emissions and the effects of global warming on cloud reflectivity.
Natural climate variability seems unlikely to have played a major role in reduced cloud cover, given that it was relatively stable until 2015. However, it is hard to fully rule it out given the relatively short satellite record.
Reductions in SO2 emissions are expected to reduce cloud reflectivity, but the magnitude of the observed cloud reflectivity changes are much larger than models simulate.
Models might be underestimating the impact of aerosols on the climate. But, if this were the case, it would indicate that climate sensitivity might be on the higher end of the range of model estimates, because models that simulate stronger aerosol cooling effects tend to have higher climate sensitivity.
Finally, cloud cover might be changing and becoming less reflective as a result of warming. Cloud responses to climate change are one of the largest drivers of uncertainty in future warming. One of the main reasons that some climate models find a higher climate sensitivity is due to their simulation of less-reflective clouds in a warming world.
The Science study concludes that the 2023 heat “may be here to stay” if the cloud-related albedo decline was not “solely” caused by natural variability. This would also suggest the Earth’s climate sensitivity may be closer to the upper range of current estimates, it notes.
Methodology
Carbon Brief built on work previously published in the IGCC 2024 and WMO state of the global climate 2024 reports that explores the role of different factors in the extreme temperatures in 2023, 2024 and 2025.
The impact of El Niño Southern Oscillation (ENSO) on the temperatures was estimated using a linear regression of the annual mean global temperature anomaly on the Feb/Mar Niño 3.4 index. This resulted in an impact of −0.07C, 0.01C and 0.13C for 2022, 2023 and 2024 respectively (with a 95% confidence interval of ±0.13 ºC).
It is important to note that the uncertainties in the ENSO response estimated here also incorporate other sources of unforced internal (modes of variability in other basins such as AMV), and potentially some forced variability. The bar in the combined figure is labelled “El Niño and variability” to reflect this.
For details on calculations of the temperature impact of shipping and Chinese SO2 declines, see Carbon Brief’s explainer on the climate impact of changing aerosol emissions.
Solar cycle 25 was both slightly earlier and slightly stronger than prior expectations with a total solar irradiance anomaly of 0.97 watts per metre squared in 2023 relative to the mean of the prior 20 years. This resulted in an estimated radiative forcing of approximately 0.17 watts per metre squared and an estimated global surface temperature increase of 0.07C (0.05C to 0.10C) with a one- to two-year lag based on a 2015 study. Thus, the impact on 2023 and 2024 is around 0.04C and 0.07C, respectively (+/- 0.025C). This is a bit higher warming than is given by the FaIR model, as the 2015 study is based on global models that have ozone responses to the UV changes, which amplifies the temperature effects a bit.
The Hunga Tonga-Hunga Haʻapai volcanic eruption added both SO2 and water vapour to the stratosphere (up to 55km in altitude). The rapid oxidation of SO2 to sulphate aerosol dominated the radiative forcing for the first two years after the eruption. As a result, the net radiative forcing at the tropopause was likely negative; −0.04 watts per metre squared and −0.15 watts per metre squared in 2022 and 2023, respectively, implying a temperature impact of -0.02C (-0.01C to -0.03C) calculated using the FaIR model.
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Analysis: What are the causes of recent record-high global temperatures?
The UK’s fleet of wind, solar and biomass power plants all set new records in 2025, Carbon Brief analysis shows, but electricity generation from gas still went up.
The rise in gas power was due to the end of UK coal generation in late 2024 and nuclear power hitting its lowest level in half a century, while electricity exports grew and imports fell.
In addition, there was a 1% rise in UK electricity demand – after years of decline – as electric vehicles (EVs), heat pumps and data centres connected to the grid in larger numbers.
Other key insights from the data include:
- Electricity demand grew for the second year in a row to 322 terawatt hours (TWh), rising by 4TWh (1%) and hinting at a shift towards steady increases, as the UK electrifies.
- Renewables supplied more of the UK’s electricity than any other source, making up 47% of the total, followed by gas (28%), nuclear (11%) and net imports (10%).
- The UK set new records for electricity generation from wind (87TWh, +5%), solar (19TWh, +31%) and biomass (41TWh, +2%), as well as for renewables overall (152TWh, +6%).
- The UK had its first full year without any coal power, compared with 2TWh of generation in 2024, ahead of the closure of the nation’s last coal plant in September of that year.
- Nuclear power was at its lowest level in half a century, generating just 36TWh (-12%), as most of the remaining fleet paused for refuelling or outages.
Overall, UK electricity became slightly more polluting in 2025, with each kilowatt hour linked to 126g of carbon dioxide (gCO2/kWh), up 2% from the record low of 124gCO2/kWh, set last year.
The National Energy System Operator (NESO) set a new record for the use of low-carbon sources – known as “zero-carbon operation” – reaching 97.7% for half an hour on 1 April 2025.
However, NESO missed its target of running the electricity network for at least 30 minutes in 2025 without any fossil fuels.
The UK inched towards separate targets set by the government, for 95% of electricity generation to come from low-carbon sources by 2030 and for this to cover 100% of domestic demand.
However, much more rapid progress will be needed to meet these goals.
Carbon Brief has published an annual analysis of the UK’s electricity generation in 2024, 2023, 2021, 2019, 2018, 2017 and 2016.
Record renewables
The UK’s fleet of renewable power plants enjoyed a record year in 2025, with their combined electricity generation reaching 152TWh, a 6% rise from a year earlier.
Renewables made up 47% of UK electricity supplies, another record high. The rise of renewables is shown in the figure below, which also highlights the end of UK coal power.
While the chart makes clear that gas-fired electricity generation has also declined over the past 15 years, there was a small rise in 2025, with output from the fuel reaching 91TWh. This was an increase of 5TWh (5%) and means gas made up 28% of electricity supplies overall.
The rise in gas-fired generation was the result of rising demand and another fall in nuclear power output, which reached the lowest level in half a century, while net imports and coal also declined.
The year began with the UK’s sunniest spring and by mid-December had already become the sunniest year on record. This contributed to a 5TWh (31%) surge in electricity generation from solar power, helped by a jump of roughly one-fifth in installed generating capacity.
The new record for solar power generation of 19TWh in 2025 comes after years of stagnation, with electricity output from the technology having climbed just 15% in five years.
The UK’s solar capacity reached 21GW in the third quarter of 2025. This is a substantial increase of 3 gigawatts (GW) or 18% year-on-year.
These are the latest figures available from the Department for Energy Security and Net Zero (DESNZ). The DESNZ timeseries has been revised to reflect previously missing data.
UK wind power also set a new record in 2025, reaching 87TWh, up 4TWh (5%). Wind conditions in 2025 were broadly similar to those in 2024, with the uptick in generation due to additional capacity.
The UK’s wind capacity reached 33GW in the third quarter of 2025, up 1GW (4%) from a year earlier. The 1.2GW Dogger Bank A in the North Sea has been ramping up since autumn 2025 and will be joined by the 1.2GW Dogger Bank B in 2026, as well as the 1.4GW Sofia project.
These sites were all awarded contracts during the government’s third “contracts for difference” (CfD) auction round and will be paid around £53 per megawatt hour (MWh) for the electricity they generate. This is well below current market prices, which currently sit at around £80/MWh.
Results from the seventh auction round, which is currently underway, will be announced in January and February 2026. Prices are expected to be significantly higher than in the third round, as a result of cost inflation.
Nevertheless, new offshore wind capacity is expected to be deliverable at “no additional cost to the billpayer”, according to consultancy Aurora Energy Research.
The UK’s biomass energy sites also had a record year in 2025, with output nudging up by 1TWh (2%) to 41TWh. Approximately two-thirds (roughly 27TWh) of this total is from wood-fired power plants, most notably the Drax former coal plant in Yorkshire, which generated 15TWh in 2024.
The government recently awarded new contracts to Drax that will apply from 2027 onwards and will see the amount of electricity it generates each year roughly halve, to around 6TWh. The government is also consulting on how to tighten sustainability rules for biomass sourcing.
Rising demand
The UK’s electricity demand has been falling for decades due to a combination of more efficient appliances and lightbulbs, as well as ongoing structural shifts in the economy.
Experts have been saying for years that at some point this trend would be reversed, as the UK shifts to electrified heat and transport supplies using EVs and heat pumps.
Indeed, the Climate Change Committee (CCC) has said that demand would more than double by 2050, with electrification forming a key plank of the UK’s efforts to reach net-zero.
Yet there has been little sign of this effect to date, with electricity demand continuing to fall outside single-year rebounds after economic shocks, such as the 2020 Covid lockdowns.
The data for 2025 shows hints that this turning point for electricity demand may finally be taking place. UK demand increased by 4TWh (1%) to 322TWh in 2025, after a 1TWh rise in 2024.
After declining for more than two decades since a peak in 2005, this is the first time in 20 years that UK demand has gone up for two years in a row, as shown in the figure below.
While detailed data on underlying electricity demand is not available, it is clear that the shift to EVs and heat pumps is playing an important role in the recent uptick.
There are now around 1.8m EVs on the UK’s roads and another 1m plug-in hybrids. Of this total, some 0.6m new EVs and plug-in hybrids were bought in 2025 alone. In addition, around 100,000 heat pumps are being installed each year. Sales of both technologies are rising fast.
Estimates from the NESO “future energy scenarios” point to an additional 2.0TWh of demand from new EVs in 2025, compared with 2024. They also suggest that newly installed heat pumps added around 0.2TWh of additional demand, while data centres added 0.4TWh.
By 2030, NESO’s scenarios suggest that electricity use for these three sources alone will rise by around 30TWh, equivalent to around 10% of total demand in 2025.
EVs would have the biggest impact, adding 17TWh to demand by 2030, NESO says, with heat pumps adding another 3TWh. Data-centre growth is highly uncertain, but could add 12TWh.
Gas growth
At the same time as UK electricity demand was growing by 4TWh in 2025, the country also lost a total of 10TWh of supply as a result of a series of small changes.
First, 2025 was the UK’s first full year without coal power since 1881, resulting in the loss of 2TWh of generation. Second, the UK’s nuclear fleet saw output falling to the lowest level in half a century, after a series of refuelling breaks and outages, which cut generation by 5TWh.
Third, after a big jump in imports in 2024, the UK saw a small decline in 2025, as well as a more notable increase in the amount of electricity exported to other countries. This pushed the country’s net imports down by 1TWh (4%).
The scale of cross-border trade in electricity is expected to increase as the UK has significantly expanded the number of interconnections with other markets.
However, the government’s clean-power targets for 2030 imply that the UK would become a net exporter, sending more electricity overseas than it receives from other countries. At present, it remains a significant net importer, with these contributions accounting for 109% of supplies.
Finally, other sources of generation – including oil – also declined in 2025, reducing UK supplies by another 2TWh, as shown in the figure below.
These losses in UK electricity supply were met by the already-mentioned increases in generation from gas, solar, wind and biomass, as shown in the figure above.
The government’s targets for decarbonising the UK’s electricity supplies will face similar challenges in the years to come as electrification – and, potentially, data centres – continue to push up demand.
All but one of the UK’s existing nuclear power plants are set to retire by 2030, meaning the loss of another 27TWh of nuclear generation.
This will be replaced by new nuclear capacity, but only slowly. The 3.2GW Hinkley Point C plant in Somerset is set to start operating in 2030 at the earliest and its sister plant, Sizewell C in Suffolk, not until at least another five years later.
Despite backing from ministers for small modular reactors, the timeline for any buildout is uncertain, with the latest government release referring to the “mid-2030s”.
Meanwhile, biomass generation is likely to decline as the output of Drax is scaled back from 2027.
Stalling progress
Taken together, the various changes in the UK’s electricity supplies in 2025 mean that efforts to decarbonise the grid stalled, with a small increase in emissions per unit of generation.
The 2% increase in carbon intensity to 126gCO2/kWh is illustrated in the figure below and comes after electricity was the “cleanest ever” in 2024, at 124gCO2/kWh.
The stalling progress on cleaning up the UK’s grid reflects the balance of record renewables, rising demand and rising gas generation, along with poor output from nuclear power.
Nevertheless, a series of other new records were set during 2025.
NESO ran the transmission grid on the island of Great Britain (GB; namely, England, Wales and Scotland) with a record 97.7% “zero-carbon operation” (ZCO) on 1 April 2025.
Note that this measure excludes gas plants that also generate heat – known as combined heat and power, or CHP – as well as waste incinerators and all other generators that do not connect to the transmission network, which means that it does not include most solar or onshore wind.
NESO was unable to meet its target – first set in 2019 – for 100% ZCO during 2025, meaning it did not succeed in running the transmission grid without any fossil fuels for half an hour.
Other records set in 2025 include:
- GB ran on 100% clean power, after accounting for exports, for a record 87 hours in 2025, up from 64.5 hours in 2024.
- Total GB renewable generation from wind, solar, biomass and hydro reached a record 31.3GW from 13:30-14:00 on 4 July 2025, meeting 84% of demand.
- GB wind generation reached a record 23.8GW for half an hour on 5 December 2025, when it met 52% of GB demand.
- GB solar reached a record 14.0GW at 13:00 on 8 July 2025, when it met 40% of demand.
The government has separate targets for at least 95% of electricity generation and 100% of demand on the island of Great Britain to come from low-carbon sources by 2030.
These goals, similar to the NESO target, exclude Northern Ireland, CHP and waste incinerators. However, they include distributed renewables, such as solar and onshore wind.
These definitions mean it is hard to measure progress independently. The most recent government figures show that 74% of qualifying generation in GB was from low-carbon sources in 2024.
Carbon Brief’s figures for the whole UK show that low-carbon sources made up a record 58% of electricity supplies overall in 2025, up marginally from a year earlier.
Similarly, low-carbon sources made up 65% of electricity generation in the UK overall. This was unchanged from a year earlier.
Methodology
The figures in the article are from Carbon Brief analysis of data from DESNZ Energy Trends, chapter 5 and chapter 6, as well as from NESO. The figures from NESO are for electricity supplied to the grid in Great Britain only and are adjusted here to include Northern Ireland.
In Carbon Brief’s analysis, the NESO numbers are also adjusted to account for electricity used by power plants on site and for generation by plants not connected to the high-voltage national grid.
NESO already includes estimates for onshore windfarms, but does not cover industrial gas combined heat and power plants and those burning landfill gas, waste or sewage gas.
Carbon intensity figures from 2009 onwards are taken directly from NESO. Pre-2009 estimates are based on the NESO methodology, taking account of fuel use efficiency for earlier years.
The carbon intensity methodology accounts for lifecycle emissions from biomass. It includes emissions for imported electricity, based on the daily electricity mix in the country of origin.
DESNZ historical electricity data, including years before 2009, is adjusted to align with other figures and combined with data on imports from a separate DESNZ dataset. Note that the data prior to 1951 only includes “major” power producers.
The post Analysis: UK renewables enjoy record year in 2025 – but gas power still rises appeared first on Carbon Brief.
Analysis: UK renewables enjoy record year in 2025 – but gas power still rises
Greenhouse Gases
Ricky Bradley named Citizens’ Climate Executive Director after strategic and legislative progress during interim leadership role
Ricky Bradley named Citizens’ Climate Executive Director after strategic and legislative progress during interim leadership role
Dec. 22, 2025 – After a six month interim period, Ricky Bradley has been appointed Executive Director of Citizens’ Climate Lobby and Citizens’ Climate Education. The decision was made by the CCL and CCE boards of directors in a unanimous vote during their final joint board meeting of 2025.
“Citizens’ Climate Lobby is fortunate to have someone with Ricky Bradley’s experience, commitment, and demeanor to lead the organization,” said CCL board chair Bill Blancato. “I can’t think of anyone with as much knowledge about CCL and its mission who is held in such high regard by CCL’s staff and volunteers.”
Bradley has been active with Citizens’ Climate for more than 13 years. Prior to his former roles as Interim Executive Director and Vice President of Field Operations, he has also served as a volunteer Group Leader and volunteer Regional Coordinator, all of which ground him in Citizens’ Climate’s grassroots model. Bradley has also led strategic planning and implementation efforts at HSBC, helping a large team adopt new approaches and deliver on big organizational goals.
“We are confident that Ricky has the skills to guide CCL during a challenging time for organizations trying to make a difference on climate change,” Blancato added.
Since stepping into the Interim Executive Director role in July 2025, Bradley has led Citizens’ Climate through a season of high volunteer engagement and effective advocacy on Capitol Hill. Under his leadership, CCL staff and volunteers organized a robust virtual lobby week with 300+ constituent meetings, despite an extended government shutdown, and executed a targeted mobilization to support the bipartisan passage of climate-friendly forestry legislation through the Senate Agriculture Committee.
“We have heard nothing but glowing descriptions of Ricky’s ability as a leader, as a manager, and as a team player,” said CCE board chair Dr. Sandra Kirtland Turner. “We’ve been absolutely thrilled with how Ricky’s brought the team together over the last six months to deliver on a new strategic plan for the organization.”
The strategic plan, which launched during CCL’s Fall Conference in November, details Citizens’ Climate’s unique role in the climate advocacy space, its theory of change for effectively moving federal climate legislation forward, and its strategic goals for 2026.
“Ricky has the heart of a CCLer and the strategic chops to take us into the next chapter as an organization,” Dr. Kirtland Turner said.
Bradley shared his vision for that next chapter in his conference opening remarks last month and, most recently, during the organization’s December monthly meeting.
“There’s a lot that we don’t control in today’s politics, but we do know who we are. The power of our persistent, nonpartisan advocacy is unmistakable,” Bradley said. “If we stay true to that, deepen our skills, and walk forward together, I know we’re going to meet this moment and deliver real results for the climate.”
CONTACT: Flannery Winchester, CCL Vice President of Marketing and Communications, 615-337-3642, flannery@citizensclimate.org
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Citizens’ Climate Lobby is a nonprofit, nonpartisan, grassroots advocacy organization focused on national policies to address climate change. Learn more at citizensclimatelobby.org.
The post Ricky Bradley named Citizens’ Climate Executive Director after strategic and legislative progress during interim leadership role appeared first on Citizens' Climate Lobby.
Greenhouse Gases
DeBriefed 19 December 2025: EU’s petrol car U-turn; Trump to axe ‘leading’ research lab; What climate scientists are reading
Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.
This week
EU easing up
HITTING THE BREAKS: The EU “walked back” its target to ban the sale of petrol and diesel cars by 2035, “permitting some new combustion engine cars”, reported Agence-France Presse. Under the original plan, the bloc would have had to cut emissions entirely by 2035 on new vehicles, but will now only have to cut emissions by 90% by that date, compared to 2021 levels. However, according to the Financial Times, some car manufacturers have “soured” on the reversal.
ADJUSTING CBAM: Meanwhile, the Financial Times reported that the EU is making plans to “close loopholes” in the bloc’s carbon border adjustment mechanism (CBAM) before it goes into effect in January. CBAM is set to be the world’s first carbon border tax and has drawn ire from key trading partners. The EU has also finalised a plan to delay its anti-deforestation legislation for another year, according to Carbon Pulse.
Around the world
- NCAR NO MORE: The Trump administration is moving to “dismantle” the National Center for Atmospheric Research in Colorado, said USA Today, describing it as “one of the world’s leading climate research labs”.
- DEADLY FLOODS: The deadliest flash flooding in Morocco in a decade killed “at least” 37 people, while residents accused the government of “ignoring known flood risks and failing to maintain basic infrastructure”, reported Radio France Internationale.
- FAILING GRADE: The past year was the “warmest and wettest” ever recorded in the Arctic, with implications for “global sea level rise, weather patterns and commercial fisheries”, according to the US National Oceanic and Atmospheric Administration’s 2025 Arctic report card, covered by NPR.
- POWER TO THE PEOPLE: Reuters reported that Kenya signed a $311m agreement with an African infrastructure fund and India’s Power Grid Corporation for the “construction of two high-voltage electricity transmission lines” that could provide power for millions of people.
- BP’S NEW EXEC: BP has appointed Woodside Energy Group’s Meg O’Neill as its new chief executive amid a “renewed push to…double down on oil and gas after retreating from an ambitious renewables strategy”, said Reuters.
29
The number of consecutive years in which the Greenland ice sheet has experienced “continuous annual ice loss”, according to a Carbon Brief guest post.
Latest climate research
- Up to 4,000 glaciers could “disappear” per year during “peak glacier extinction”, projected to occur sometime between 2041 and 2055 | Nature Climate Change
- The rate of sea level rise across the coastal US doubled over the past century | AGU Advances
- Repression and criminalisation of climate and environmentally focused protests are a “global phenomena”, according to an analysis of 14 countries | Environmental Politics
(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 latest coal market report from the International Energy Agency said that global coal use will reach record levels in 2025, but will decline by the end of the decade. Carbon Brief analysis of the report found that projected coal use in China for 2027 has been revised downwards by 127m tonnes, compared to the projection from the 2024 report – “more than cancelling out the effects of the Trump administration’s coal-friendly policies in the US”.
Spotlight
What climate scientists are curious about
This week, Carbon Brief spoke to climate scientists attending the annual meeting of the American Geophysical Union in New Orleans, Louisiana, about the most interesting research papers they read this year.
Their answers have been lightly edited for length and clarity.
Dr Christopher Callahan, assistant professor at Indiana University Bloomington
The most interesting research paper I read was a simple thought experiment asking when we would have known humans were changing the climate if we had always had perfect observations. The authors show that we could have detected a human influence on the climate as early as the 1880s, since we have a strong physical understanding of how those changes should look. This paper both highlights that we have been discernibly changing the climate for centuries and emphasises the importance of the modern climate observing network – a network that is currently threatened by budget cuts and staff shortages.
Prof Lucy Hutyra, distinguished professor at Boston University
The most interesting paper I read was in Nature Climate Change, where the researchers looked at how much mortality was associated with cold weather versus hot weather events and found that many more people died during cold weather events. Then, they estimated how much of a protective factor in the urban heat island is on those winter deaths and suggested that the winter benefits exceed the summer risks of mitigating extreme heat, so perhaps we shouldn’t mitigate extreme heat in cities.
This paper got me in a tizzy…It spurred an exciting new line of research. We’ll be publishing a response to this paper in 2026. I’m not sure their conclusion was correct, but it raised really excellent questions.
Dr Kristina Dahl, vice president for science at Climate Central
This year was when we saw source attribution studies, such as Chris Callahan‘s, really start to break through and be able to connect the emissions of specific emitters…to the impact of those emissions through heat or some other sort of damage function. [This] is really game-changing.
What [Callahan’s] paper showed is that the emissions of individual companies have an impact on extreme heat, which then has an impact on the GDP of the countries experiencing that extreme heat. And so, for the first time, you can really say: “Company X caused this condition which then led to this economic damage.”
Dr Antonia Hadjimichael, assistant professor at Pennsylvania State University
It was about interdisciplinary work – not that anything in it is ground-shakingly new, but it was a good conversation around interdisciplinary teams and what makes them work and what doesn’t make them work. And what I really liked about it is that they really emphasise the role of a connector – the scientist that navigates this space in between and makes sure that the things kind of glue together…The reason I really like this paper is that we don’t value those scientists in academia, in traditional metrics that we have.
Dr Santiago Botía, researcher at Max Planck Institute for Biogeochemistry
The most interesting paper I’ve read this year was about how soil fertility and water table depth control the response to drought in the Amazon. They found very nicely how the proximity to soil water controls the anomalies in gross primary productivity in the Amazon. And, with that methodology, they could explain the response of recent droughts and the “greening” of the forest during drought, which is kind of a counterintuitive [phenomenon], but it was very interesting.
Dr Gregory Johnson, affiliate professor at the University of Washington
This article explores the response of a fairly coarse spatial resolution climate model…to a scenario in which atmospheric CO2 is increased at 1% a year to doubling and then CO2 is more gradually removed from the atmosphere…[It finds] a large release of heat from the Southern Ocean, with substantial regional – and even global – climate impacts. I find this work interesting because it reminds us of the important – and potentially nonlinear – roles that changing ocean circulation and water properties play in modulating our climate.
Cecilia Keating also contributed to this spotlight.
Watch, read, listen
METHANE MATTERS: In the Guardian, Barbados prime minister Mia Mottley wrote that the world must “urgently target methane” to avoid the worst impacts of climate change.
CLIMATE WRAPPED: Grist summarised the major stories for Earth’s climate in 2025 – “the good, the bad and the ugly”.
COASTING: On the Coastal Call podcast, a biogeochemist spoke about “coastal change and community resilience” in the eastern US’s Long Island Sound.
Coming up
- 27 December: Cote D’Ivoire parliamentary elections
- 28 December: Central African Republic presidential and parliamentary elections
- 28 December: Guinean presidential election
Pick of the jobs
- BirdLife International, forest programme administrator | Salary: £28,000-£30,000. Location: Cambridge, UK
- World Resources Institute, power-sector transition senior manager | Salary: $116,000-$139,000. Location: Washington DC
- Fauna & Flora, operations lead for Liberia | Salary: $61,910. Location: Monrovia, Liberia
DeBriefed is edited by Daisy Dunne. Please send any tips or feedback to debriefed@carbonbrief.org.
This is an online version of Carbon Brief’s weekly DeBriefed email newsletter. Subscribe for free here.
The post DeBriefed 19 December 2025: EU’s petrol car U-turn; Trump to axe ‘leading’ research lab; What climate scientists are reading appeared first on Carbon Brief.
What Has Happened in the United States Recently
Current Events Can Be Depressing
The United States Descends into Darkness
Guest post: Why China is still building new coal – and when it might stop
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