The UK would be able to increase its emissions while still meeting its next legally binding climate goal if the government uses a “surplus” to weaken the target, official advisers warn.
The government has asked the Climate Change Committee (CCC) if it should carry over “surplus” emissions, after the UK overachieved the third “carbon budget” for 2018-2022.
This surplus is equivalent to an extra year’s worth of emissions, so carrying it forward would increase the size of the fourth carbon budget for 2023-2027 by a fifth.
Doing so would make it far easier for the next government to meet that budget, allowing emissions to rise by around 15% from current levels – instead of falling towards net-zero.
In a letter, published today, the Climate Change Committee (CCC) says its “unequivocal” advice is that doing this would place the UK’s future climate goals at “very serious risk” and would make the 2050 net-zero target “more expensive and harder to achieve”.
The letter says that the surplus is largely the result of a sluggish economy and the impact of Covid-19. The committee emphasises that the UK’s emissions cuts need to accelerate to stay on course for long-term goals, rather than slow down.
‘Surplus’ emissions cuts
Under the Climate Change Act, the UK must hit legally binding interim emissions targets, known as carbon budgets, that get gradually lower on a pathway to net-zero emissions by 2050.
Earlier this month, the government published final greenhouse gas emissions figures showing that the UK overachieved in its third carbon budget. Total net emissions were 2,153m tonnes of carbon dioxide equivalent (MtCO2e) between 2018 and 2022, the figures show, against a target of 2,544MtCO2e.
This means the UK came in 391MtCO2e – or 15% – below the budget for this five-year period. This “overachievement”, largely due to the impact of the Covid-19 pandemic and other external factors (see below), is equivalent to around one year of UK emissions.
Earlier this month, UK climate minister Graham Stuart asked the CCC for its view on “carrying forward” the emissions “surplus” to the next carbon budget.
Under section 17 of the Climate Change Act, the government is legally entitled to do this if it wishes, but must first seek and take into account the CCC’s advice.
Carrying forward some or all of the surplus effectively weakens the UK’s next carbon budget, by an equivalent amount. Nevertheless, the flexibility was included in the Climate Change Act in order to encourage – and reward – early action to cut emissions.
Five years ago, the CCC issued a similar warning that the UK should not carry forward the surplus from the second carbon budget to the third period, because that overachievement was also largely due to external factors rather than genuine early action.
However, the government ignored the CCC’s advice – the first time it had done so – and carried forward 88MtCO2e into the third carbon budget.
Today, the CCC has once again written to the government warning it not to weaken the fourth carbon budget by making use of surplus emissions.
Indeed, as the chart below shows, making full use of the third budget surplus would allow the UK to legally increase its emissions in the current fourth carbon budget period 2024-2027, rather than cutting them in line with its longer-term goals.
With the third carbon budget surplus of 391MtCO2e being equivalent to a whole extra year of emissions in the UK, the country could emit around 20% more over the five-year budget than the amount officially legislated.
Adding this amount to the fourth carbon budget would enable the UK to emit 200MtCO2e more between 2023-27 than it did over the course of its third carbon budget, following decades of relatively consistent cuts.
This would amount to a 9% increase in emissions between budgets and an increase of as much as 15% from 2022 levels, across the fourth budget period.
It would also push the UK far off course from the government’s own carbon budget delivery plan for meeting near- and long-term targets, which it set out last year.
If the government decides to carry over the surplus and emissions are allowed to rise to their maximum level under a looser fourth carbon budget, getting back on track for the fifth carbon budget would require a “huge and impractical” total emissions reduction of 1,036MtCO2e over the following five years, according to the CCC.
This is twice as fast as anticipated in the government’s plan – and 40% quicker than the most ambitious scenario devised by the CCC.
‘Very serious risk’
In light of these potential outcomes, interim CCC chair Prof Piers Forster writes in his response to Stuart’s request that the surplus should not be used:
“The committee’s unequivocal advice is that surplus emissions from the third carbon budget should not be carried forward.”
The committee warns against “setting conditions that allow for a legally compliant slowdown in progress” when the focus “should be on accelerating and broadening emissions reductions”.
It concludes that both the UK’s domestic goal of the sixth carbon budget for 2033-37 and its 2030 international climate target under the Paris Agreement would be placed at “very serious risk” if the carryover is allowed.
The fourth carbon budget was set when the UK’s 2050 emissions goal was an 80% reduction rather than 100%. This means that the government should be overachieving, rather than underachieving, on the budget’s target emissions reductions in order to stay on a “sensible” track for its future goals, according to the CCC.
The CCC’s response reiterates its previous recommendations to Stuart’s predecessors about carrying forward surplus from the first and second carbon budgets.
Moreover, the committee points out that “most” of the surplus emissions cuts in recent years have not been the result of the government’s climate policies.
According to the committee, roughly half of them resulted from a “tighter than expected” EU ETS cap. This meant “less was required” of government policy in areas outside of the ETS, such as transport and heating buildings.
Most of the remaining surplus is accounted for by “lower-than-expected GDP” and less travel due to the Covid-19 pandemic, the CCC adds.
The CCC emphasises the need for continued incentives and pressure to make emissions cuts across all sectors, concluding:
“The Climate Change Act and the carbon budgets provide a clear, longrun signal to investors and businesses on the UK’s decarbonisation trajectory. Carrying forward the third carbon budget surplus would weaken this message, causing uncertainty, and could ultimately result in net-zero being more expensive and harder to achieve.”
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UK emissions could rise by 15% if government uses ‘surplus’ to weaken climate goal, CCC warns
Drought and heatwaves occurring together – known as “compound” events – have “surged” across the world since the early 2000s, a new study shows.
Compound drought and heat events (CDHEs) can have devastating effects, creating the ideal conditions for intense wildfires, such as Australia’s “Black Summer” of 2019-20 where bushfires burned 24m hectares and killed 33 people.
The research, published in Science Advances, finds that the increase in CDHEs is predominantly being driven by events that start with a heatwave.
The global area affected by such “heatwave-led” compound events has more than doubled between 1980-2001 and 2002-23, the study says.
The rapid increase in these events over the last 23 years cannot be explained solely by global warming, the authors note.
Since the late 1990s, feedbacks between the land and the atmosphere have become stronger, making heatwaves more likely to trigger drought conditions, they explain.
One of the study authors tells Carbon Brief that societies must pay greater attention to compound events, which can “cause severe impacts on ecosystems, agriculture and society”.
Compound events
CDHEs are extreme weather events where drought and heatwave conditions occur simultaneously – or shortly after each other – in the same region.
These events are often triggered by large-scale weather patterns, such as “blocking” highs, which can produce “prolonged” hot and dry conditions, according to the study.
Prof Sang-Wook Yeh is one of the study authors and a professor at the Ewha Womans University in South Korea. He tells Carbon Brief:
“When heatwaves and droughts occur together, the two hazards reinforce each other through land-atmosphere interactions. This amplifies surface heating and soil moisture deficits, making compound events more intense and damaging than single hazards.”
CDHEs can begin with either a heatwave or a drought.
The sequence of these extremes is important, the study says, as they have different drivers and impacts.
For example, in a CDHE where the heatwave was the precursor, increased direct sunshine causes more moisture loss from soils and plants, leading to a drought.
Conversely, in an event where the drought was the precursor, the lack of soil moisture means that less of the sun’s energy goes into evaporation and more goes into warming the Earth’s surface. This produces favourable conditions for heatwaves.
The study shows that the majority of CDHEs globally start out as a drought.
In recent years, there has been increasing focus on these events due to the devastating impact they have on agriculture, ecosystems and public health.
In Russia in the summer of 2010, a compound drought-heatwave event – and the associated wildfires – caused the death of nearly 55,000 people, the study notes.
The record-breaking Pacific north-west “heat dome” in 2021 triggered extreme drought conditions that caused “significant declines” in wheat yields, as well as in barley, canola and fruit production in British Columbia and Alberta, Canada, says the study.
Increasing events
To assess how CDHEs are changing, the researchers use daily reanalysis data to identify droughts and heatwaves events. (Reanalysis data combines past observations with climate models to create a historical climate record.) Then, using an algorithm, they analyse how these events overlap in both time and space.
The study covers the period from 1980 to 2023 and the world’s land surface, excluding polar regions where CDHEs are rare.
The research finds that the area of land affected by CDHEs has “increased substantially” since the early 2000s.
Heatwave-led events have been the main contributor to this increase, the study says, with their spatial extent rising 110% between 1980-2001 and 2002-23, compared to a 59% increase for drought-led events.
The map below shows the global distribution of CDHEs over 1980-2023. The charts show the percentage of the land surface affected by a heatwave-led CDHE (red) or a drought-led CDHE (yellow) in a given year (left) and relative increase in each CDHE type (right).
The study finds that CDHEs have occurred most frequently in northern South America, the southern US, eastern Europe, central Africa and south Asia.
Threshold passed
The authors explain that the increase in heatwave-led CDHEs is related to rising global temperatures, but that this does not tell the whole story.
In the earlier 22-year period of 1980-2001, the study finds that the spatial extent of heatwave-led CDHEs rises by 1.6% per 1C of global temperature rise. For the more-recent period of 2022-23, this increases “nearly eightfold” to 13.1%.
The change suggests that the rapid increase in the heatwave-led CDHEs occurred after the global average temperature “surpasse[d] a certain temperature threshold”, the paper says.
This threshold is an absolute global average temperature of 14.3C, the authors estimate (based on an 11-year average), which the world passed around the year 2000.
Investigating the recent surge in heatwave-leading CDHEs further, the researchers find a “regime shift” in land-atmosphere dynamics “toward a persistently intensified state after the late 1990s”.
In other words, the way that drier soils drive higher surface temperatures, and vice versa, is becoming stronger, resulting in more heatwave-led compound events.
Daily data
The research has some advantages over other previous studies, Yeh says. For instance, the new work uses daily estimations of CDHEs, compared to monthly data used in past research. This is “important for capturing the detailed occurrence” of these events, says Yeh.
He adds that another advantage of their study is that it distinguishes the sequence of droughts and heatwaves, which allows them to “better understand the differences” in the characteristics of CDHEs.
Dr Meryem Tanarhte is a climate scientist at the University Hassan II in Morocco, and Dr Ruth Cerezo Mota is a climatologist and a researcher at the National Autonomous University of Mexico. Both scientists, who were not involved in the study, agree that the daily estimations give a clearer picture of how CDHEs are changing.
Cerezo-Mota adds that another major contribution of the study is its global focus. She tells Carbon Brief that in some regions, such as Mexico and Africa, there is a lack of studies on CDHEs:
“Not because the events do not occur, but perhaps because [these regions] do not have all the data or the expertise to do so.”
However, she notes that the reanalysis data used by the study does have limitations with how it represents rainfall in some parts of the world.
Compound impacts
The study notes that if CDHEs continue to intensify – particularly events where heatwaves are the precursors – they could drive declining crop productivity, increased wildfire frequency and severe public health crises.
These impacts could be “much more rapid and severe as global warming continues”, Yeh tells Carbon Brief.
Tanarhte notes that these events can be forecasted up to 10 days ahead in many regions. Furthermore, she says, the strongest impacts can be prevented “through preparedness and adaptation”, including through “water management for agriculture, heatwave mitigation measures and wildfire mitigation”.
The study recommends reassessing current risk management strategies for these compound events. It also suggests incorporating the sequences of drought and heatwaves into compound event analysis frameworks “to enhance climate risk management”.
Cerezo-Mota says that it is clear that the world needs to be prepared for the increased occurrence of these events. She tells Carbon Brief:
“These [risk assessments and strategies] need to be carried out at the local level to understand the complexities of each region.”
The post Heatwaves driving recent ‘surge’ in compound drought and heat extremes appeared first on Carbon Brief.
Heatwaves driving recent ‘surge’ in compound drought and heat extremes
Greenhouse Gases
DeBriefed 6 March 2026: Iran energy crisis | China climate plan | Bristol’s ‘pioneering’ wind turbine
Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.
This week
Energy crisis
ENERGY SPIKE: US-Israeli attacks on Iran and subsequent counterattacks across the Middle East have sent energy prices “soaring”, according to Reuters. The newswire reported that the region “accounts for just under a third of global oil production and almost a fifth of gas”. The Guardian noted that shipping traffic through the strait of Hormuz, which normally ferries 20% of the world’s oil, “all but ground to a halt”. The Financial Times reported that attacks by Iran on Middle East energy facilities – notably in Qatar – triggered the “biggest rise in gas prices since Russia’s full-scale invasion of Ukraine”.
‘RISK’ AND ‘BENEFITS’: Bloomberg reported on increases in diesel prices in Europe and the US, speculating that rising fuel costs could be “a risk for president Donald Trump”. US gas producers are “poised to benefit from the big disruption in global supply”, according to CNBC. Indian government sources told the Economic Times that Russia is prepared to “fulfil India’s energy demands”. China Daily quoted experts who said “China’s energy security remains fundamentally unshaken”, thanks to “emergency stockpiles and a wide array of import channels”.
‘ESSENTIAL’ RENEWABLES: Energy analysts said governments should cut their fossil-fuel reliance by investing in renewables, “rather than just seeking non-Gulf oil and gas suppliers”, reported Climate Home News. This message was echoed by UK business secretary Peter Kyle, who said “doubling down on renewables” was “essential” amid “regional instability”, according to the Daily Telegraph.
China’s climate plan
PEAK COAL?: China has set out its next “five-year plan” at the annual “two sessions” meeting of the National People’s Congress, including its climate strategy out to 2030, according to the Hong Kong-based South China Morning Post. The plan called for China to cut its carbon emissions per unit of gross domestic product (GDP) by 17% from 2026 to 2030, which “may allow for continued increase in emissions given the rate of GDP growth”, reported Reuters. The newswire added that the plan also had targets to reach peak coal in the next five years and replace 30m tonnes per year of coal with renewables.
ACTIVE YET PRUDENT: Bloomberg described the new plan as “cautious”, stating that it “frustrat[es] hopes for tighter policy that would drive the nation to peak carbon emissions well before president Xi Jinping’s 2030 deadline”. Carbon Brief has just published an in-depth analysis of the plan. China Daily reported that the strategy “highlights measures to promote the climate targets of peaking carbon dioxide emissions before 2030”, which China said it would work towards “actively yet prudently”.
Around the world
- EU RULES: The European Commission has proposed new “made in Europe” rules to support domestic low-carbon industries, “against fierce competition from China”, reported Agence France-Presse. Carbon Brief examined what it means for climate efforts.
- RECORD HEAT: The US National Oceanic and Atmospheric Administration has said there is a 50-60% chance that the El Niño weather pattern could return this year, amplifying the effect of global warming and potentially driving temperatures to “record highs”, according to Euronews.
- FLAGSHIP FUND: The African Development Bank’s “flagship clean energy fund” plans to more than double its financing to $2.5bn for African renewables over the next two years, reported the Associated Press.
- NO WITHDRAWAL: Vanuatu has defied US efforts to force the Pacific-island nation to drop a UN draft resolution calling on the world to implement a landmark International Court of Justice (ICJ) ruling on climate, according to the Guardian.
98
The number of nations that submitted their national reports on tackling nature loss to the UN on time – just half of the 196 countries that are part of the UN biodiversity treaty – according to analysis by Carbon Brief.
Latest climate research
- Sea levels are already “much higher than assumed” in most assessments of the threat posed by sea-level rise, due to “inadequate” modelling assumptions | Nature
- Accelerating human-caused global warming could see the Paris Agreement’s 1.5C limit crossed before 2030 | Geophysical Research Letters covered by Carbon Brief
- Future “super El Niño events” could “significantly lower” solar power generation due to a reduction in solar irradiance in key regions, such as California and east China | Communications Earth & Environment
(For more, see Carbon Brief’s in-depth daily summaries of the top climate news stories on Monday, Tuesday, Wednesday, Thursday and Friday.)
Captured
UK greenhouse gas emissions in 2025 fell to 54% below 1990 levels, the baseline year for its legally binding climate goals, according to new Carbon Brief analysis. Over the same period, data from the World Bank shows that the UK’s economy has expanded by 95%, meaning that emissions have been decoupling from growth.
Spotlight
Bristol’s ‘pioneering’ community wind turbine
Following the recent launch of the UK government’s local power plan, Carbon Brief visits one of the country’s community-energy success stories.
The Lawrence Weston housing estate is set apart from the main city of Bristol, wedged between the tree-lined grounds of a stately home and a sprawl of warehouses and waste incinerators. It is one of the most deprived areas in the city.
Yet, just across the M5 motorway stands a structure that has brought the spoils of the energy transition directly to this historically forgotten estate – a 4.2 megawatt (MW) wind turbine.
The turbine is owned by local charity Ambition Lawrence Weston and all the profits from its electricity sales – around £100,000 a year – go to the community. In the UK’s local power plan, it was singled out by energy secretary Ed Miliband as a “pioneering” project.
‘Sustainable income’
On a recent visit to the estate by Carbon Brief, Ambition Lawrence Weston’s development manager, Mark Pepper, rattled off the story behind the wind turbine.
In 2012, Pepper and his team were approached by the Bristol Energy Cooperative with a chance to get a slice of the income from a new solar farm. They jumped at the opportunity.
“Austerity measures were kicking in