A man walks on a hot summer day in Srinagar, India-controlled Kashmir, July 25, 2024
SCIENTISTS say four billion people — about half the world’s population — experienced at least one extra month of extreme heat from May 2024 to May 2025 because of human-caused climate change.
The extreme heat caused illness, death, crop losses and strained energy and healthcare systems, according to the analysis from World Weather Attribution, Climate Central and the Red Cross.
“Although floods and cyclones often dominate headlines, heat is arguably the deadliest extreme event,” the report said.
Many heat-related deaths are unreported or are mislabelled by other conditions like heart disease or kidney failure.
The study shows how much climate change boosted temperatures in an extreme heat event and calculated how much more likely its occurrence was because of climate change.
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Global yields of wheat are around 10% lower now than they would have been without the influence of climate change, according to a new study.
The research, published in the Proceedings of the National Academy of Sciences, looks at data on climate change and growing conditions for wheat and other major crops around the world over the past 50 years.
It comes as heat and drought have this year been putting wheat supplies at risk in key grain-producing regions, including parts of Europe, China and Russia.
The study finds that increasingly hot and dry conditions negatively impacted yields of three of the five key crops examined.
Overall, global grain yields soared during the study period due to technological advancements, improved seeds and access to synthetic fertilisers.
But these yield setbacks have “important ramifications for prices and food security”, the study authors write.
Grain impacts
Most parts of the world have experienced “significant” yield increases in staple crops since the mid-20th century.
The new study notes that, in the past 50 years, yields increased by 69-123% for the five staple crops included in the research – wheat, maize, barley, soya beans and rice.
But crop production is increasingly threatened by climate change and extreme weather. A 2021 study projected “major shifts” in global crop productivity due to climate change within the next two decades.
Earlier this year, Carbon Brief mapped out news stories of crops being destroyed around the world by heat, drought, floods and other weather extremes in 2023-24. Maize and wheat were the crops that appeared most frequently in these reports.
The crops that appeared most frequently in media reports of extreme weather impacts analysed by Carbon Brief, ranked in order of most to least frequent: maize, wheat, rice, potatoes, soya beans, olives, bananas, grapes, sunflowers and coffee. Credit: Carbon Brief.
Hot and dry weather is currently threatening wheat crops in parts of China, the world’s largest wheat producer, Reuters reported this month.
In the UK, wheat crops are struggling amid the “driest start to spring in England for almost 70 years”, the Times recently reported. Farm groups say some crops are already failing, the Guardian said.
As a result, global wheat supplies are “tight”, according to Bloomberg, with price rises possible depending on weather conditions in parts of Europe, China and Russia.
Food security and prices
The study uses climate datasets, modelling and national crop statistics from the UN Food and Agriculture Organization to assess crop production and climate trends in key grain-producing countries over 1974-2023, including Argentina, Brazil, Canada, China, the EU, Russia and the US.
The researchers assess climate observations and then use crop models to calculate what yields would have been with and without these climate changes.
For example, “if it has warmed 1C over 50 years and the model says that 1C leads to 5% yield loss, we’d calculate that the warming trend caused a loss of 5%”, Prof David Lobell, the lead study author and a professor at Stanford University, tells Carbon Brief.
The study looks at two reanalysis climate datasets that include information on temperature and rainfall over the past 50 years: TerraClimate (TC) and ERA5-Land. (Reanalysis data combines observations with a modern forecasting model.)
The researchers find that yields of three of the five crops are lower than they would have been without warmer temperatures and other climate impacts in the past 50 years.
Yields were lower than they otherwise would have been by 12-14% for barley, 8-12% for wheat and 4% for maize.
The impacts on soya beans were less clear as there were “significant differences” between data sources. But both datasets show a negative impact on yields, ranging from 2% to 8%.
The effects on rice yields were inconclusive, with one dataset showing a positive effect of around 1% while the other showed a negative effect of about 3%.
The chart below shows the estimated yield impacts for each crop based on the calculations from the two climate datasets.
The estimated percentage impact of climate factors on yields of wheat (brown), maize (yellow), rice (blue), soya bean (green) and barley (purple) from 1974-2023, using two different historical climate datasets. Source: Lobell et al. (2025).
Given soaring overall crop yields during this time, impacts of 4-13% “may seem trivial”, the researchers write. But, they say, it can have “important ramifications for prices and food security” given growing food demand, noting:
“The overall picture of the past half-century is that climate trends have led to a deterioration of growing conditions for many of the main grain-producing regions of the world.”
Water stress and heat
The study also assesses the impacts that warming and vapour pressure deficit – a key driver of plant water stress – have on crop yields.
Vapour pressure deficit is the difference between the amount of water vapour in the air and the point at which water vapour in the air becomes saturated. As air becomes warmer, it can hold more water vapour.
A high deficit can reduce plant growth and increase water stress. The models show that these effects may be the main driver of losses in grain yield, with heat having a more “indirect effect”, as higher temperatures drive water stress.
Agricultural irrigation system watering dry soil on a crop field in the US. Credit: Andrii Biletskyi / Alamy Stock Photo.
The study finds that vapour pressure deficit increased in most temperate regions in the past 50 years.
The researchers compare their data to climate modelling simulations covering the past 50 years. They find largely similar results, but notice a “significant underestimation” of vapour pressure deficit increases in temperate regions in most climate models.
Many maize-growing areas in the EU, China, Argentina and much of Africa have vapour deficit trends that “exceed even the highest trend in models”, they write.
The researchers also find that most regions experienced “rapid warming” during the study period, with the average crop-growing season now warmer than more than 80% of growing seasons 50 years ago.
The findings indicate that, in some areas, “even the coolest growing season in the present day is warmer than the warmest season that would have occurred 50 years ago”.
An exception to this is in the US and Canada, they find, with most maize and soya bean crop areas in the US experiencing lower levels of warming than other parts of the world and a “slight cooling” in wheat-growing areas of the northern Great Plains and central Canada.
(The central US has experienced a cooling trend in summer daytime temperatures since the middle of the 20th century, according to the National Oceanic and Atmospheric Administration. There are many theories behind this “warming hole”, which has continued despite climate change.)
CO2 greening
Dr Corey Lesk, a postdoctoral researcher at Dartmouth College who studies the impacts of climate on crops, says these findings are in line with other recent estimates. He tells Carbon Brief:
“There are some uncertainties and sensitivity to model specification here – but it’s somewhat likely climate change has already reduced crop yields in the global mean.”
The study’s “main limitation” is that it is “behind” on including certain advances in understanding how soil moisture impacts crops, Lesk adds:
“Moisture changes and CO2 [carbon dioxide] effects are the largest present uncertainties in past and future crop impacts of climate change. This paper is somewhat limited in advancing understanding on those aspects, but it’s illuminating to pause and take stock.”
The research looks at whether the benefits of CO2 increases during the past 50 years exceed the negative effects of higher levels of the greenhouse gas.
Rising CO2 levels can boost plant growth in some areas in a process called “CO2 fertilisation”. However, a 2019 study found that this “global greening” could be stalled by growing water stress.
Yield losses for wheat, maize and barley “likely exceeded” any benefits of CO2 increases in the past 50 years, the study finds.
The opposite is true for soya beans and rice, they find, with a net-positive impact of more than 4% on yields.
Soya beans growing in a field. Credit: Volodymyr Shtun / Alamy Stock Photo.
Climate science has “done a remarkable job of anticipating global impacts on the main grains and we should continue to rely on this science to guide policy decisions”, Lobell, the lead study author, says in a press release.
He adds that there may be “blind spots” on specialised crops, such as coffee, cocoa, oranges and olives, which “don’t have as much modelling” as key commodity crops, noting:
“All these have been seeing supply challenges and price increases. These matter less for food security, but may be more eye-catching for consumers who might not otherwise care about climate change.”
Lobell et al. (2025), A half-century of climate change in major agricultural regions: Trends, impacts, and surprises, Proceedings of the National Academy of Sciences, doi:10.1073/pnas.2502789122
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A “blocking” weather system lingering high above the UK has produced one of the driest, warmest and brightest starts to spring on record.
April 2025 was the sunniest since records began in 1910. This followed the third-sunniest March, and both months saw temperatures well above average nationwide. On May 1, the temperature reached 29.3°C in Kew Gardens in London – a new record for the date.
Meteorologists are warning of the potential for a summer drought, as the UK has seen roughly half its usual amount of rainfall for March and April. While farmers fret about this year’s harvest, some water companies are urging customers to help reservoir levels recover by limiting water use.
Meanwhile, wildfires have engulfed forest and moorland in areas of Scotland, Wales and England.
Most of the UK has experienced a record-dry spring so far. Met Office
For several weeks, a stubborn area of high pressure over the UK has diverted the usual flow of mild, moist air from the North Atlantic like a boulder in a river. This is known as a blocking weather system.
Within it, air descends, warms and dries, which is why this weather pattern tends to be linked to heatwaves and drought. Blocking is usually persistent, making it seem like the weather is stuck.
Here’s how climate change may have played a role in setting up this unusual spring.
The warming climate means that unusually warm weather is occurring more often and becoming more intense. At the same time, we can expect more periods of both severe drought and extreme rainfall. Sudden changes from drought to deluge, termed “weather whiplash”, are due to the intensification of the water cycle in a warmer atmosphere that can hold more water vapour.
However, certain weather patterns are necessary to produce extreme weather. More blocking events in future could increase the chance of heatwaves or drought. But are blocking weather patterns becoming more common?
It’s difficult to determine how weather patterns will change as a result of the rising concentration of greenhouse gases in the atmosphere, which is predominantly caused by the burning of fossil fuels.
Part of the difficulty arises from the fact that weather patterns vary year to year. Several years in a row with more blocking events than usual could make it seem like blocking is increasing due to climate change, but it could simply be down to chance.
As a result, it is difficult to detect the fingerprint of human activity from weather observations alone. For example, blocking weather patterns over Greenland during summer have happened more often in recent decades, which can enhance the melting of the ice sheet. But it isn’t clear that this trend is the result of human-induced climate change.
Climate models do suggest future changes in the occurrence of blocking, however. These computer simulations, consisting of equations that describe the fundamental physics of the atmosphere, are the main tool scientists use to perform experiments that parse how the climate will behave in future.
When scientists run climate model simulations with increased greenhouse gas concentrations the results consistently show a decrease in blocking events. But blocking generally happens more often in real life than model simulations, which reduces the confidence scientists have in future projections.
Keeping track of the jet stream
The movement of weather systems in Earth’s mid-latitudes – including over the UK – is linked to the jet stream, which is a fast-flowing river of air driven by the contrast in temperature between the poles and mid-latitudes.
Some researchers have suggested that, because the Arctic is warming faster than the tropics, the jet stream may weaken and become more “wavy”, increasing the occurrence of blocking events, contrary to what most climate models show.
Outside of the scientific community, this idea has become popular. However, the hypothesis remains controversial among scientists, and observational evidence has weakened in recent years.
In fact, around ten kilometres above the Earth’s surface, near commercial aircraft cruising altitudes, the opposite trends are occurring: the temperature difference between the Arctic and mid-latitudes is increasing, acting to increase the strength of the jet stream.
There are considerable challenges with understanding how climate change is affecting the large-scale atmospheric patterns which drive the weather we experience. These include large natural variability and imperfect climate models. Models mostly suggest a decline in blocking events with climate change, though this remains relatively uncertain compared with other aspects of the science.
Overall, we can be confident that climate change is bringing warmer conditions in all seasons. Scientists also have strong evidence to suggest that drought conditions will become more common. These changes are already affecting food production, energy generation and water availability and these impacts will continue to worsen with climate change.
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 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 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 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, 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
Reform Party leader Nigel Farage celebrates his party candidate Sarah Pochin winning the Runcorn and Helsby byelection by six votes Photograph: Anthony Devlin/Getty Images
The head of the UK’s biggest union has urged staff at Reform UK-controlled councils to sign up after Nigel Farage warned workers to seek “alternative careers”.
Farage said during a speech on Friday that he would advise council staff working on diversity or climate change initiatives to seek “alternative careers very, very quickly” after Reform UK took control of Durham county council.
The Clacton MP’s party made major gains in Thursday’s local elections, picking up 10 councils and more than 600 seats. The party also won two mayoral races and secured a fifth MP in Runcorn and Helsby with Sarah Pochin.
Responding to Farage’s comments, Unison general secretary Christina McAnea said: “Unions are there to ensure no one can play fast and loose with the law.
“Any staff working for councils now controlled by Reform, and who aren’t yet members, should sign up so they can be protected too.”
Farage has said he wants a British equivalent of Doge – referring to the Elon Musk’s so-called “department of government efficiency”, which is slashing government spending in the US, in every council.
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A man walks on a hot summer day in Srinagar, India-controlled Kashmir, July 25, 2024
