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Children born in 2020 will face ‘unprecedented exposure’ to climate extremes

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Original article republished from Carbon Brief under a CC license. 

Children drink water from a pipeline in the village of Afraaga, Somaliland. Credit: Joe Giddens / Alamy Stock Photo

Children born in 2020 will face “unprecedented exposure” to extreme weather events, including heatwaves, droughts and wildfires, even if warming is limited to 1.5C above pre-industrial temperatures.

That is according to a new study, published in Nature, which calculates the number of unprecedented extreme events that people born in different decades and countries might live through.

Using a case study focused on Brussels, the researchers find that people born in 2020 will experience an “unprecedented” 11 heatwaves in their lifetime – even if global warming is limited to 1.5C by the end of the century.

In contrast, in a pre-industrial climate, a person living in the Belgian capital would likely experience just three such heatwaves, according to the study.

More than half of children born in 2020 – around 62 million people – will experience “unprecedented lifetime exposure” to heatwaves, even if warming is limited to 1.5C, the study finds. 

However, this number nearly doubles to 111 million under a scenario where warming hits 3.5C.

The study also analyses crop failures, river floods, tropical cyclones, wildfires and droughts. 

The research “helps the climate community build new narratives that better clarify the impacts [of climate change] on younger generations and vulnerable populations”, one expert who was not involved in the study tells Carbon Brief.

Intergenerational justice

As the planet warms, extreme weather events such as heatwaves, floods and droughts are becoming more intense, more frequent and lasting longer.

A popular 2021 study found that children born in the 21st century will be exposed to more extreme weather events in their lifetimes than their parents and grandparents.

The paper found that in a scenario of 3C of warming above pre-industrial levels, a child who turns six in 2020 will experience twice as many wildfires and tropical cyclones, three times more river floods, four times more crop failures, five times more droughts and 36 times more heatwaves over their lifetime than a six-year-old living in a pre-industrial climate.

The authors also found a “particularly strong increase” in children’s future exposure to extremes in the Middle East and North Africa.

The lead author of the study – Prof Wim Thiery from Vrije Universiteit Brussel – told Carbon Brief at the time that today’s youth will live “an unprecedented life”, in which they will “face conditions which older generations have never experienced”.

Four years later, Dr Luke Grant – a researcher in Thiery’s team – has led a new study building on the ideas of the 2021 paper.

Grant tells Carbon Brief that rather than counting the number of extreme events that an individual might experience, his new study counts the number of people that reach an “unprecedented state” of exposure to extremes.

Prof Kaveh Madani is the director of the UN University Institute for Water, Environment and Health and was not involved in the study. He tells Carbon Brief that the paper “helps the climate community build new narratives that better clarify the impacts [of climate change] on younger generations and vulnerable populations”.

The authors define “exposure” as the number of extreme events that a person experiences in their lifetime, relative to the number they would have experienced in a pre-industrial climate.

“Unprecedented lifetime exposure” is defined as exposure so high that it has only a one-in-10,000 chance of happening in a world without any greenhouse gas emissions.

‘Unprecedented lifetime exposure’

The authors present a case study of extreme heat in Brussels, Belgium, to explain their method.

They define a heatwave as a three-day extreme heat event, which reaches average temperatures that would be expected once per century in a pre-industrial climate.

Using models from the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP), the authors calculate heatwave frequency in a world without climate change. They also assess scenarios in which warming is limited to 1.5C, 2.5C and 3.5C by the end of the century.

They combine this data with demographic information, including how many people are born in the country each year and their average life expectancy, using data from sources including the ISIMIP database and UN population estimates and projections.

In a world without climate change, the study finds that a person born in 1960 in Brussels would have a one-in-10,000 chance of experiencing six of the pre-defined heatwaves in their lifetime. Any member of this “birth cohort” who experiences more than six heatwaves in their lifetime has therefore faced “unprecedented lifetime exposure” to extreme heat, according to the study.

The authors find that a person born in Brussels in 1960 is likely to experience three heatwaves on average during their lives under all of the three future warming pathways– meaning that they are unlikely to face “unprecedented lifetime exposure” to heat.

By contrast, the researchers find that many younger age cohorts will experience unprecedented heatwave exposure. For many younger age cohorts, lifetime exposure to heatwaves is greater for higher warming pathways. 

For example, people born in Brussels in 2020 will experience 11 heatwaves in their lifetime if global warming is limited to 1.5C by the end of the century. If warming rises to 2.5C or 3.5C, they could experience 18 or 26 heatwaves, respectively. 

The graphic below shows heat exposure since birth in Brussels for three “birth cohorts” of 1960 (bottom row), 1990 (middle row) and 2020 (top row). It presents three future scenarios, in which warming is limited to 1.5C (blue), 2.5C (yellow) and 3.5C (red) by 2100. The dotted line shows the threshold for an “unprecedented” lifetime exposure to extreme heat. 

Lifetime exposure to unprecedented heat for people born in Brussels
Lifetime exposure to unprecedented heat for people born in Brussels in 1960 (bottom row), 1990 (middle row) and 2020 (top row), under scenarios that limit warming to 1.5C (blue), 2.5C (yellow) and 3.5C (red) by the year 2100. The dotted line shows the threshold for an “unprecedented” lifetime exposure to extreme heat. Source: Grant et al (2025).

Heat exposure

The authors repeat their analysis across the Earth’s entire land surface, by dividing it into grid cells and using location-specific temperature and demographic data. 

Of the 81 million people born in 1960, they find that 13 million are likely to face unprecedented exposure to heatwaves in their lifetimes. They add that for this age cohort, lifetime exposure to unprecedented extremes does not vary depending on the warming scenario.

However, 21st century warming has a significant effect on exposure for younger generations. Under a 1.5C warming pathway, 52% of people born in 2020 will face unprecedented exposure to heatwaves. This rises to 92% under a 3.5C warming scenario.

The study adds:

“This implies that 111 million children born in 2020 will live an unprecedented life in terms of heatwave exposure in a world that warms to 3.5C versus 62 million in a 1.5C pathway.”

The charity Save the Children has published a report which unpacks the findings of the study. The graphic below, from the report, shows the percentage of people from different countries born in 2020 who will face unprecedented lifetime exposure to heatwaves under the 1.5C (top), 2.5C (middle) and 3.5C (bottom) warming scenarios.

Each circle shows a country, indicated by its three-letter countries code. The size of the circle indicates the number of people in the country. Darker circles indicate higher-income countries. 

Circles on the right hand side of the graphic indicate that more than half of the country’s 2020 cohort will be exposed to unprecedented heatwaves in their lifetime. 

The percentage of people born in 2020 who will face unprecedented lifetime exposure to heatwaves
The percentage of people born in 2020 who will face unprecedented lifetime exposure to heatwaves under the 1.5C (top), 2.5C (middle) and 3.5C (bottom) warming scenarios. Each circle indicates a country, indicated by its three-letter countries code. The size of the circle indicates the number of people in the country. Darker circles indicate higher-income countries. Source: Save the Children

“The evidence is now inescapable that heatwaves impact every community around the world,” Dr Luke Harrington, a senior lecturer in environmental science at the University of Waikato, who was not involved in the study, tells Carbon Brief. He adds: 

“This paper offers the clearest view that climate change is verifiably unfair: those who have done the least to contribute to rising global temperatures will experience the most extreme impacts.”

From floods to fires

The authors apply the same method to five other climate extremes – crop failure, wildfires, droughts, floods and tropical cyclones.

The graphic below shows the key findings. The coloured portion of the bar shows the number of people born in 2020 who will face unprecedented exposure to each extreme under a 1.5C warming pathway. The dark green and light green bars show the additional exposure under 2.7C and 3.5C warming.

Number of people born in 2020 who will face “unprecedented lifetime exposure” to heatwaves, crop failures, river floods, tropical cyclones, wildfires and droughts
Number of people born in 2020 who will face “unprecedented lifetime exposure” to heatwaves, crop failures, river floods, tropical cyclones, wildfires and droughts under 1.5C 2.7C and 3.5C warming. Source: Save the Children

The authors find that unprecedented lifetime exposure to heatwaves will affect the most people, with 62 million people born in 2020 likely to face unprecedented exposure to heat in their lifetimes if warming is limited to 1.5C.

This is followed by crop failures and river floods, which will impact 23 million and 10 million people from the 2020 birth cohort under the 1.5C warming pathway, respectively.

Lead author Grant tells Carbon Brief that he is “most confident” about his heatwave findings because temperature is a “basic” metric for climate models to “get right”.

Meanwhile, extremes such as crop failure depend on a range of factors including soil moisture, land-atmosphere interactions and rainfall, which can make it harder for the models to accurately capture changes, Grant explains.

Vulnerability

The authors also assess how “socioeconomic vulnerability” affects their findings using a global deprivation index – a tool which measures the level of disadvantage and hardship experienced by individuals or communities in a particular geographic area.

The authors use the index to identify the 20% most and least vulnerable people in each age cohort. They find that the most vulnerable groups are overwhelmingly from African countries.

The authors also conclude that “socioeconomically vulnerable people have a consistently higher chance of facing unprecedented lifetime heatwave exposure compared to the least vulnerable members of their generation”.

The graph below, taken from a news and views article about the study, shows the percentage of high vulnerability (red) and low vulnerability (pink) people in each age cohort who would be exposed to unprecedented heat, under a 2.7C warming scenario. 

The percentage of high vulnerability (red) and low vulnerability (pink) people in each age cohort who would be exposed to unprecedented heat,
The percentage of high vulnerability (red) and low vulnerability (pink) people in each age cohort who would be exposed to unprecedented heat, under a 2.7C warming scenario. Source: Gualdi and Muttarak (2025).

Dr Marina Romanello, a research fellow at the University College London and research director of the Lancet Countdown on Health and Climate Change who was not involved in the study, tells Carbon Brief that the paper “is an important addition to the scientific literature, showing how our delays in tackling climate change are putting the future of our children at risk”. 

She adds:

“The authors have used well-established models to project future health threats, framing them around what matters the most: the wellbeing, health and survival of present and future generations.”

Grant, L. et al. (2025) Global emergence of unprecedented lifetime exposure to climate extremes, Nature, doi:10.1038/s41586-025-08907-1

Original article republished from Carbon Brief under a CC license. 

Continue ReadingChildren born in 2020 will face ‘unprecedented exposure’ to climate extremes

Reeves’s Heathrow third runway report was commissioned by London airport

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https://www.theguardian.com/environment/2025/feb/01/reevess-heathrow-third-runway-report-was-commissioned-by-london-airport

The chancellor is under fire after a study cited as evidence for expanding the terminal to boost the UK’s economic growth was ordered by Heathrow itself

Rachel Reeves was facing criticism on Saturday night as it was confirmed that a report she cited as evidence that a third ­runway at Heathrow would boost the UK economy was commissioned by the airport itself.

Experts and green groups also challenged Reeves’s view that advances in the production of ­sustainable aviation fuel (SAF) had been a “gamechanger” that would substantially limit the environmental damage of flying, ­saying the claims were overblown and did not stand up to scrutiny.

…

Alex Chapman, senior economist at the NEF, said: “It is very concerning that the chancellor appears to be basing her support for Heathrow expansion on a figure from a report commissioned by Heathrow airport.

“Even more worrying is the fact that the methodology they have applied is one that the Department for Transport has previously decided is not fit for purpose, and that the report uses forecast data supplied by the airport itself.

“Heathrow expansion represents a major threat to the UK’s climate goals and flies in the face of scientific advice. To ensure that the claimed economic benefits are concrete, assessments should be carried out by independent government economists following best-practice methodology.

“NEF’s analysis has identified a wide range of weaknesses in the economic case, which have emerged since it was last fully appraised in 2015. Not least, the decline of business air travel, the surge in outbound leisure travel and the negative impacts on wider regions of the UK – all of which erode the potential growth benefit.”

Analysis by climate crisis website Carbon Brief suggests that, using the government’s own figures, SAF will barely cut emissions by 2040, and any reduction will be wiped out by rising flight numbers.

…

https://www.theguardian.com/environment/2025/feb/01/reevess-heathrow-third-runway-report-was-commissioned-by-london-airport

Continue ReadingReeves’s Heathrow third runway report was commissioned by London airport

Analysis: UK would need forest ‘twice size of London’ to offset new airport expansion

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Original article by Josh Gabbatiss Verner Viisainen republished from Carbon Brief.

Planes queuing for takeoff at Heathrow airport in Britain. Credit: david pearson / Alamy Stock Photo

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.

Annual UK aviation emissions, MtCO2e.
Annual UK aviation emissions, MtCO2e. The blue line indicates the trajectory for emissions set out by the CCC. The three red lines indicate the additional emissions that would result from the expansion of Heathrow, Gatwick and Luton airports, plus the resulting flights. The airport expansions are assumed to follow approximate timelines based on their respective planning applications, with some dates assumed based on the views of AEF. The Heathrow expansion is assumed to be in operation in 2035 and at full capacity by 2040. The Gatwick expansion is assumed to be operational in 2028 and at full capacity by 2038. The Luton expansion is assumed to be operational in 2033 and at full capacity by 2043. Sources: DESNZ, CCC, AEF, airport planning documents.

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.

Original article by Josh Gabbatiss Verner Viisainen republished from Carbon Brief.

Continue ReadingAnalysis: UK would need forest ‘twice size of London’ to offset new airport expansion

Interview: Prof Philippe Sands on UN court’s landmark climate-change hearing

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Interview: Prof Philippe Sands on UN court’s landmark climate-change hearing

This week, the international court of justice (ICJ) opened two weeks of hearings on states’ climate-related legal obligations – and the consequences, if “significant harm” is caused.

The case stems from a unanimous UN general assembly (UNGA) request for an “advisory opinion” from the ICJ.

It is taking place against a backdrop of rapidly escalating climate impacts. Emissions continue to rise, rather than falling rapidly, as needed to avoid dangerous levels of global warming.

It is the ICJ’s largest ever case, with more than 100 countries and international organisations making interventions, deploying a wide variety of legal arguments.

Ralph Regenvanu, climate envoy for Vanuatu, which led the campaign for the ICJ hearings, said in his opening address: “[T]his may well be the most consequential case in the history of humanity.”

Below, Carbon Brief interviews leading international law scholar Prof Philippe Sands – who drafted the pleadings for Mauritius, but is speaking here in a personal capacity – to find out more about the legal issues at stake and the wider significance of the ICJ case.

Carbon Brief: Would you be able to start by just situating this case in its wider legal context and explaining why it could be so consequential?

Philippe Sands: Well, it’s the first time the international court of justice has been called upon to address legal issues relating to climate change. The ICJ is the principal judicial organ of the United Nations and, although the advisory opinion that it hands down will not be binding on states, it is binding on all UN bodies. The determinations that the court makes will have consequences that go very far and that will have a particular authority, in legal and political terms. Of course, everything turns on what the court actually says.

CB: Would you be able to summarise the key legal arguments that are being fought over in this case?

PS: No! I mean, there’s just a huge number of issues that are coming up. But, essentially, the court has been asked two questions by the UN General Assembly – the first time, I believe, that a request from the General Assembly has been consensual, with no objections. The two questions are, firstly, what are the obligations for states under international law to protect the climate system? And, secondly, what are the legal consequences under these obligations, where, by their acts and emissions, [states] cause significant harm to the climate system? So, there are two distinct questions – and about 100 states and international organisations of various kinds have made submissions on the vast range of issues that are raised by these two questions. The questions are very, very broad and that signals to me that the court’s response may be quite general. But, for me, the crucial issues are, firstly, what the court says about the state of the science: is it established, or is there any room for doubt? Secondly, what are the obligations of states having regard to the clarity of the science? Thirdly, are there legal obligations on states in relation to the climate system that exist and arise outside of the treaty regime – the 1992 [UN Framework] convention [on climate change], the Kyoto Protocol, the Paris Agreement and so on and so forth. And, related to that, fourthly – this is the most intense, legally interesting aspect – what are the responsibilities of states for historic emissions under general international law? And, in particular, are the biggest contributors liable under international law to make good any damages that may arise from their historic actions? But, I mean, there’s just such a vast array of questions that are addressed, it’s impossible to summarise briefly.

… Article continues at https://www.carbonbrief.org/interview-prof-philippe-sands-on-un-courts-landmark-climate-change-hearing/

On climate change, the international court of justice faces a pivotal choice

Continue ReadingInterview: Prof Philippe Sands on UN court’s landmark climate-change hearing

State of the climate: 2024 will be first year above 1.5C of global warming

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Original article by Zeke Hausfather republished from Carbon Brief under a CC license.

This year is now virtually certain to beat 2023 as the hottest year on record, Carbon Brief analysis shows.

It will also be the first full year to surpass 1.5C above pre-industrial levels across the majority of observational records.

In this latest “state of the climate” quarterly update, Carbon Brief finds:

  • The year 2024 has seen record warm temperatures for seven of the nine months of the year where data is so far available.
  • The world, as a whole, has warmed approximately 1C since 1970 – and 1.2C to 1.4C since the mid-1800s.
  • A strong El Niño event contributed to exceptionally high global temperatures early in the year, but record or near-record temperatures persisted despite the fading of El Niño in recent months.
  • Record global temperatures have been seen across many regions of the planet over the first nine months of the year.
  • Global temperatures are closely aligned with the projections from climate models.
  • Global sea ice extent is currently at record lows and Antarctic sea ice has spent much of the year at near-record lows – second only to those seen in 2023.

The warmest year on record

In this latest quarterly state of the climate assessment, Carbon Brief has analysed records from five different research groups that report global surface temperature records: NASA’s GISTEMP; NOAA’s GlobalTemp; Hadley/UEA’s HadCRUT5; Berkeley Earth; and Copernicus/ECMWF. 

The figure below shows Carbon Brief’s estimate of where 2024 temperatures will end up in each of the groups, based on the year to date and expected El Niño-Southern Oscillation (ENSO) conditions in the tropical Pacific for the remainder of the year. 

The dots reflect the best estimate, while the whiskers show the two sigma (95%) confidence interval of the projections. The prior record year (2023 in all groups) is shown by the coloured square. https://interactive.carbonbrief.org/state-of-the-climate/24-Q3/projections.htmlCarbon Brief’s project of 2024 annual global average surface temperatures for each group, along with 95% confidence intervals and prior record (2023) values. 1.5C above pre-industrial (1850-1900) levels is shown by a dashed line. The average projection represents a composite of all five records following the WMO approach. Chart by Carbon Brief.

In all cases, the projected global average temperature for 2024 is virtually certain to exceed the prior record set in 2023. 

Three of the five groups (Hadley, Berkeley and Copernicus/ECMWF) are very likely to show annual temperatures exceeding 1.5C above pre-industrial levels (defined here as the 1850-1900 period), while the NASA record has a roughly 40% chance of exceeding 1.5C. Only NOAA’s record is unlikely to show global temperatures above 1.5C this year.

These differences in warming since pre-industrial across different datasets primarily result from choice of ocean records used, as well as differences in approaches to filling in gaps between observations in the early part of the records (e.g. pre-1900s). It reflects the uncertainty in the degree of warming since the mid-1800s, with projected 2024 temperatures ranging from 1.44C (NOAA) to 1.61C (Berkeley Earth).

The figure also provides a composite average of the five different datasets, following the approach used in the sixth assessment report (AR6) from the Intergovernmental Panel on Climate Change (IPCC) and by the WMO. Carbon Brief’s analysis finds that 2024 will be the first year above 1.5C in the composite average. 

This provides a way to determine the first year where we can reasonably say that the world has passed that warming level – even though 2023 exceeded 1.5C in the Berkeley Earth dataset and 2024 will not exceed 1.5C in the NOAA dataset.

(It is important to note that exceeding 1.5C in a single year is not equivalent to breaching the Paris Agreement limit. The goal is generally considered to refer to long-term warming – typically over two or three decades – rather than annual temperatures that include the short-term influence of natural fluctuations in the climate, such as El Niño.)

The figure below shows the annual temperatures from each of these groups between 1970 and present, with the year-to-date 2024 temperatures for each record shown as individual points. https://interactive.carbonbrief.org/state-of-the-climate/24-Q3/records_2024_to_date.htmlAnnual global average surface temperatures from NASA GISTEMP, NOAA GlobalTemp, Hadley/UEA HadCRUT5, Berkeley Earth and Copernicus/ECMWF (lines), along with 2024 temperatures to date (January-September, coloured shapes). Each series is aligned by using a 1981-2010 baseline, with warming since pre-industrial based on the IPCC AR6 estimate of warming between pre-industrial and the 1981-2010 period. Chart by Carbon Brief.

There is strong agreement between the different temperature records, with all of them showing approximately 1C warming between 1970 and present. Global temperatures have been around 1.3 above pre-industrial levels in recent years (with a range of 1.2C to 1.4C across the different temperature datasets, reflecting that the differences between them are larger in the 1800s and early 1900s).

As the chart below shows, 2024 (purple line) started out remarkably warm as a result of a strong El Niño event that built in 2023 (red) and peaked near the beginning of the year. 

However, global temperatures have remained quite elevated despite the fading of El Niño conditions, setting records through June and remaining quite close to 2023’s exceptional highs in recent months. 

Overall, 2024 has set or tied all-time records for seven of the 10 months available to-date in the ERA5 record. (This record uses weather model-based reanalysis to combine lots of different data sources over time.)https://interactive.carbonbrief.org/state-of-the-climate/24-Q3/monthly_global_temperature_anomalies_Q3_2024.htmlTemperatures for each month from 1940 to 2024 from Copernicus/ECMWF ERA5. Anomalies plotted with respect to a 1850-1900 baseline. Chart by Carbon Brief.

While human emissions of CO2 and other greenhouse gases are responsible for effectively all of the Earth’s long-term warming, temperatures in any given year are strongly influenced by short-term variations in the Earth’s climate that are typically associated with El Niño and La Niña events. 

These fluctuations in temperature between the ocean and atmosphere in the tropical Pacific help make some individual years warmer and some cooler. 

The figure below shows a range of different ENSO forecast models produced by different scientific groups. The values shown are sea surface temperature variations in the tropical Pacific – the El Niño 3.4 region – for three-month periods.

El Niño Southern Oscillation (ENSO) forecast models for overlapping three-month periods in the Niño3.4 region
El Niño Southern Oscillation (ENSO) forecast models for overlapping three-month periods in the Niño3.4 region (July, August, September – JAS – and so on) for the remainder of 2024 and then into the spring and summer of 2025. Credit: CPC/IRI ENSO forecast.

Most models expect neutral conditions in the tropical Pacific, with only a few crossing the -0.5C Niño 3.4 sea surface temperature (SST) anomaly that represents the development of a formal La Niña event. 

This should result in relatively cooler temperatures in 2025, though it is possible that the year ends up warmer than anticipated given the continuation of high temperatures in recent months – despite the absence of El Niño conditions.

Large areas of record warmth

While global average temperatures are an important indicator of changes to the broader climate system over time as a result of human activities, these impacts will differ as some regions experience more rapid warming or extreme heat events than is reflected in the global average.

The figure below shows the parts of the world that saw record warm or cold temperatures over the first three quarters of 2024 (January through to September) in the Berkeley Earth dataset compared to all prior years since global temperature record began in 1850.

Map of year-to-date (January-September) regions that set new records (warmest through to fifth warmest). Note that no regions set cold records for the year-to-date in 2024.
Map of year-to-date (January-September) regions that set new records (warmest through to fifth warmest). Note that no regions set cold records for the year-to-date in 2024. Credit: Berkeley Earth

Notably, no area on Earth saw record cold (or even the second, third, fourth or fifth coldest temperatures on record). Nearly all of Central America and large parts of South America saw their warmest year to date on record, as did much of eastern Europe, Africa, China, south-east Asia, and Korea. 

The figure below shows the temperature anomaly over the first nine months of the year compared to the 1951-80 baseline period used by Berkeley Earth. Warming was particularly pronounced over land regions, with many areas already showing warming of 1.5C or 2C above that baseline.

Map of year-to-date (January-September) global surface temperatures. Anomalies are shown relative to the 1951-80 period following the convention used by Berkeley Earth.
Map of year-to-date (January-September) global surface temperatures. Anomalies are shown relative to the 1951-80 period following the convention used by Berkeley Earth. Credit: Berkeley Earth

Temperatures are tracking climate model projections

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

The figure below shows the range of individual models forecasts featured in AR6 – known collectively as the CMIP6 models – between 1970 and 2030, with grey shading and the average projection across all the models shown in black. Individual observational temperature records are represented by coloured lines.https://interactive.carbonbrief.org/state-of-the-climate/24-Q3/model_obs_comps_Q3_2024.htmlTwelve-month average global average surface temperatures from CMIP6 models and observations between 1970 and 2024. Models use SSP2-4.5 forcings after 2015.Anomalies plotted with respect to a 1981-2010 baseline. Chart by Carbon Brief.

While global temperatures were running below the pace of warming projected by climate models for much of the period between 2008 and 2022, the past two years have been closer to the model average. 

However, the CMIP6 models may be biassed a bit too warm, with a subset of “hot” models pushing up the average. The IPCC used an approach that weighted models based on how well they reproduced historical temperatures, rather than simply averaging all the models together.

Excluding these hotter models from the analysis results in observations over recent years much closer to the multi-model average and near the centre of the uncertainty range across all models. It also reveals that the past two years – 2023 and 2024 – have been near the upper end of the model range.https://interactive.carbonbrief.org/state-of-the-climate/24-Q3/model%20_obs_comps_filtered_Q3_2024.htmlTwelve-month average global average surface temperatures from CMIP5 models and observations between 1970 and 2024. Models use SSP2-4.5 forcings after 2015. Anomalies plotted with respect to a 1981-2010 baseline. Chart by Carbon Brief.

Record low global sea ice extent

Highly accurate observations of Arctic and Antarctic sea ice have been available since polar-observing satellites became available in the late 1970s. 

Arctic sea ice extent during the first three-quarters of 2024 has been below or at the low end of the historical 1979-2010 range, but has not seen any record daily lows. 

Antarctic sea ice, on the other hand, set new all-time low records for a few days in July and September, and has generally been the second lowest on record (after 2023) from June onwards.

The figure below shows both Arctic (red) and Antarctic (blue) sea ice extent in 2024, the historical range in the record between 1979 and 2010 (shaded areas) and the record lows (dotted black line).

Unlike global temperature records (which only report monthly averages), sea ice data is collected and updated on a daily basis, allowing sea ice extent to be viewed through to the present day.https://interactive.carbonbrief.org/state-of-the-climate/24-Q3/sea_ice.htmlArctic and Antarctic daily sea ice extent from the US National Snow and Ice Data Center. The bold lines show daily 2024 values, the shaded area indicates the two standard deviation range in historical values between 1979 and 2010. The dotted black lines show the record lows for each pole. Chart by Carbon Brief.

Global sea ice extent is estimated by combining both Arctic and Antarctic sea ice extent. The figure below shows global sea ice extent in each year, with 2024 shown in red. Currently global sea ice extent is at record-low levels, below the prior record for this date set in 2023.

Global sea ice extent

Methodological note

A statistical multivariate regression model was used to estimate the range of likely 2024 annual temperatures for each group that provides a temperature record. This model used the average temperature over the first six months of the year, the average ENSO 3.4 region value during the first nine months of the year and the average predicted ENSO 3.4 value during the last three months of the year to estimate the annual temperatures. 

The model was trained on the relationship between these variables and annual temperatures over the period of 1950-2023. The model then uses this fit to predict both the most likely 2024 annual value for each group, as well as the 95% confidence interval. The predicted ENSO 3.4 region values for the last three months of 2024 are taken from the IRI plume forecast.

The percent likelihood of different year ranks for 2024 is estimated by using the output of the regression model, assuming a normal distribution of results. This allows Carbon Brief to estimate what percent of possible 2024 annual values fall above and below the temperatures of prior years for each group, as well as the likelihood of the year exceeding 1.5C in each record.

Original article by Zeke Hausfather republished from Carbon Brief under a CC license.

Continue ReadingState of the climate: 2024 will be first year above 1.5C of global warming