A forest twice the size of Greater London would need to be planted in the UK to cancel out the extra emissions from the expansion of Heathrow, Gatwick and Luton airports, Carbon Brief analysis reveals.
New runaways at these airports surrounding London would result in cumulative emissions of around 92m tonnes of extra carbon dioxide equivalent (CO2e) by 2050, if the number of flights increases in line with their operating company targets.
If the UK is to remain on track for net-zero, it would need to cut emissions further in other sectors of the economy or remove an equivalent amount from the atmosphere.
For example, offsetting these emissions would require more than 300,000 hectares of trees to be planted within just a few years. This equates to all the trees planted in the UK since 2000.
The Labour government is set to back all three airport expansions, according to media reporting ahead of a speech by chancellor Rachel Reeves this week.
This is in spite of opposition from within the Labour party and the government’s climate advisors recommending against airport expansion.
Reeves has stressed that “sustainable aviation fuels” (SAFs) and electric planes could help to offset these emissions.
However, such technologies are still in the early stages of deployment and previous Carbon Brief analysis suggests the role of SAFs in achieving net-zero may be limited.
Two Londons
Reeves is expected to reveal plans for a third runway at Heathrow in a speech on Wednesday.
This, alongside suggestions she will also announce her support for the expansion of Gatwick and Luton airports, has prompted days of political debate over the friction between the government’s climate and economic plans.
Reeves sees the expansion of airports as a key part of the government’s “growth strategy”. However, senior Labour politicians, notably energy secretary Ed Miliband, have previously opposed such expansions on environmental grounds.
For her part, the chancellor told BBC News that she thought “sustainable aviation and economic growth go hand in hand”.
Carbon Brief has used estimates of passenger numbers from the airports’ planning applications, combined with assumptions used by UK government advisors the Climate Change Committee (CCC), to calculate emissions from the three expansions.
As the chart below shows, the CCC assumes aviation emissions fall in the coming years due to technological and efficiency improvements.
However, the expansion of Heathrow, Gatwick and Luton would drive an uptick in emissions around 2040 as the projects are completed, if the expected number of extra flights take off and if there are no additional improvements in aircraft efficiency.
This would amount to an additional 92MtCO2e being emitted cumulatively by 2050.
In order to remain on track for the UK’s net-zero target, these emissions would need to be avoided by additional technological innovations in the aviation sector, balanced by faster cuts in other parts of the economy – or removed from the atmosphere after being emitted.
Aviation is generally viewed as a difficult sector to decarbonise, due to the lack of cheap and effective technologies to cut emissions from planes.
This is why campaigners and researchers frequently stress demand reduction as the most effective way to cut aviation emissions.
The UK’s net-zero plans already allow for aviation to be one of the final sectors producing sizable volumes of emissions in 2050, when most of the economy has decarbonised.
One strategy to remove the excess emissions from the additional Heathrow, Gatwick and Luton flights would be to plant more trees. However, this would be a significant undertaking, as Carbon Brief analysis shows.
It would require planting around 301,000 hectares of new forest by around 2028 so that the trees are large enough by the middle of the century to absorb significant amounts of CO2.
This is equivalent to around twice the size of Greater London, which covers 157,000 hectares. It is 10 times higher than the UK’s most recent annual tree-planting target and equates to all of the trees planted in the past 24 years across the country.
More passengers
Government advisors at the CCC have recommended that there should be no more than a 25% growth in the number of air passengers from 2018 levels, in order to meet the UK’s net-zero goal by 2050.
This amounts to an increase from 292 million passengers to 365 million by 2050. The number of UK flights collapsed during Covid-19 lockdowns and has been slow to recover to pre-pandemic levels, but the number of air passengers in 2023 reached 273 million.
The CCC has consistently stressed that there should be “no net increase” in airport capacity if the UK is to reach net-zero by the middle of the century, meaning any expansion is “balanced by reductions in capacity elsewhere”. It has also stated there should be no airport expansion without a UK-wide framework for managing capacity.
The committee criticised the previous Conservative government for setting “no plans” to limit growth in passenger numbers in its “jet-zero” strategy, which envisaged demand for flying increasing by 70% out to 2050.
Airport expansion at Heathrow, Gatwick and Luton would help bring the total number of passengers at these three sites up to 243 million in 2050, according to the airports’ own planning applications, compiled by the Aviation Environment Federation (AEF).
This amounts to an additional 100m passengers passing through these airports, compared to 2018 levels. This would bring the total number of UK passengers to 392 million – equivalent to a 34% increase in UK airport traffic – meaning that growth at Heathrow, Gatwick and Luton alone would be enough to breach the CCC’s guidance.
(In reality, more than 20 UK airports have plans for more capacity and some already have unused capacity, so it is unlikely that expansion would be limited to three airports around London.)
SAF concerns
The CCC leaves some flexibility in its advice to the government, allowing for future capacity growth, if “the carbon intensity of aviation is outperforming the government’s emissions reduction pathway”.
Essentially, if clean technologies slash aviation emissions faster than expected, then there will be space for more flights within a pathway to net-zero by 2050.
This has been alluded to by Reeves in recent days. She has stated that a “lot has changed in terms of aviation” and reportedly based an internal proposal to expand Heathrow on the use of “sustainable aviation fuels” (SAFs).
In reality, there has been very limited progress in developing SAFs or any other technologies to decarbonise planes in the UK. In 2023, the CCC chastised the Conservative government for “rel[ying] heavily on nascent technologies”.
Government modelling has shown SAFs will have a limited impact on cutting UK aviation emissions. Experts have pointed to the issues with the supply of materials for making SAFs and noted that none of the five SAF plants originally pegged to start construction in the UK this year are being built yet.
Methodology
This analysis is based on the CCC’s sixth carbon budget “balanced pathway” for the aviation sector, combined with data obtained from AEF on the expected increase in passenger numbers from the expansion of Heathrow, Gatwick and Luton airports.
The CCC pathway assumes that the emissions per passenger fall from 0.14 tCO2 in 2020 to 0.06tCO2 in 2050, accounting for the rollout of SAF and more efficient aircraft. It also assumes that no net expansion of airport capacity occurs.
Therefore, in this analysis, the three airport expansions are considered additional to the emissions included within the CCC pathway.
To calculate the additional emissions from the expansion of the three airports, the additional passenger numbers this would facilitate are multiplied by the emissions intensity per passenger in each year of the CCC pathway.
The additional passenger numbers from each airport are added to a Department for Transport pathway that assumes no further expansion. Each airport expansion is assumed to ramp up linearly from the year of operation to the year of operation at full additional capacity.
Based on the airport planning applications and AEF, it is assumed that:
- The Heathrow expansion will be operational by 2035 and operating at full capacity by 2040.
- The Gatwick expansion will be operational by 2028 and operating at full capacity by 2038.
- The Luton expansion will be operational by 2033 and operating at full capacity by 2043.
The calculated CO2 removals from planting trees are based on assumptions used by the CCC’s sixth carbon budget “balanced pathway”, in which there is a 2:1 ratio of conifers to broadleaves planted across the country.
The CO2 removals per hectare for conifers and broadleaves are taken from the UK Centre for Ecology and Hydrology (CEH), whose numbers are also used by the CCC.
Based on these numbers, the cumulative emissions removed per hectare of forest after 22 years – from the start of airport expansion in 2028 to 2050 – is 304tCO2. Dividing this value by the total additional cumulative emissions from the airport expansion (92 MtCO2), gives a total area required of 301,000ha. Given that Greater London is 157,200ha, this corresponds to approximately two (1.91) times the area of Greater London.
Historical UK aviation emissions are taken from the Department of Energy Security and Net Zero (DESNZ) up to 2022. For 2023 and 2024, the emissions are estimated based on percentage annual changes in UK jet fuel use, which are then applied to the emissions from 2022.
The post Analysis: UK would need forest ‘twice size of London’ to offset new airport expansion appeared first on Carbon Brief.
Analysis: UK would need forest ‘twice size of London’ to offset new airport expansion
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
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