For the past two decades, low-level cloud cover has been declining, increasing the amount of sunlight absorbed by Earth and amplifying global warming.
As global temperatures have reached record highs in recent years, there has been concern that the decline in cloudiness may be enhancing warming more than previously expected.
In a new study, published in Atmospheric Chemistry and Physics Letters, we investigate how the decline in global cloudiness affects the Earth’s “energy imbalance” – the difference between absorbed solar energy and heat radiated into space that results in global warming.
This imbalance has more than doubled over the past 20 years, as greenhouse gases have trapped more heat in the atmosphere.
We find that, since 2003, the decrease of cloudiness has been responsible for half of the increase of Earth’s energy imbalance.
Analysing the drivers of global changes to cloud cover, we find that the decrease in cloudiness over the past two decades has been primarily driven by humans, rather than being caused by natural variations in Earth’s climate.
Taken together, our findings mean that scientists can even more confidently attribute recent warming to human activities.
Low-level clouds and warming
Low-level clouds are those that have a base below 6,500 feet (2,000 metres) above Earth and include stratus, stratocumulus and cumulus. They are typically found over large areas of the global ocean, where there is a large moisture supply from evaporation.
These clouds have a powerful impact on the Earth’s climate because they reflect a substantial fraction of incoming sunlight back into space.
By acting as the Earth’s “sunscreen”, they keep the climate cooler than it would otherwise be.
Satellite observations reveal a global decline in these low-level clouds since the turn of the millennium. This is shown in the chart below, where the black line represents the average percentage of the Earth covered by low-level clouds and the dashed line the downward trend.
Our research shows that the decline in cloudiness over the past 20 years has played a major role in increasing the Earth’s energy imbalance and, therefore, warming.
The Earth’s energy imbalance is the difference between the amount of energy arriving at the Earth from the sun and what is reflected and radiated back to space.
Rising greenhouse gas emissions from human activity are upsetting this balance by trapping more energy in the atmosphere, leading to warming.
A less cloudy atmosphere also helps supercharge the energy imbalance, because it means more sunlight reaches the Earth.
In our research, we use a simple model to assess how changes in low-level clouds between July 2003 and June 2024 contributed to the Earth’s energy imbalance.
We find that, averaged globally, changes in low-level cloudiness caused an extra 0.22 watts per metre squared (W/m2) per decade of absorbed sunlight. This amounts to exactly half of the concurrent increase in Earth’s energy imbalance over the same time period.
This is shown in the chart below, where the green line represents the increase in the Earth’s energy imbalance over 2003-24 and the black line shows the contribution of low-level clouds to that trend.
Why is cloudiness changing?
Scientists have attributed declining cloud cover in the 21st century to three main causes.
The first is a decrease in human-caused aerosol emissions over recent decades. Aerosols – tiny, light‑scattering particles produced mainly by burning fossil fuels – influence the formation of clouds, by acting as “seeds” for cloud droplets to form.
In recent years, aerosol emissions have been reduced due to efforts to clean up air pollution, such as cleaner shipping fuel regulations. Cleaner air has resulted in a decline in cloudiness.
Second, increasing concentration of greenhouse gases in the atmosphere has led to a warmer and drier atmosphere, which also helps to dissipate clouds.
Although a warmer atmosphere generally holds more water vapour in absolute terms, what matters for clouds is the “relative humidity” of the air, which has been declining in many places. This is a measure of how “saturated” the air is, or how much water vapour the air contains compared to the maximum it could hold.
Finally, cloud cover decreases have also been linked to ocean surface warming, which affects atmospheric humidity and, thus, cloudiness. Reduced cloudiness leads to more sunlight being absorbed at the ocean surface – and more warming. This amplifying loop is known as a “cloud feedback”.
However, the exact strength of these three effects on cloud cover is still unclear.
In fact, cloud feedbacks are among the main uncertainties in climate model projections of global warming.
Attributing low-cloud cover changes
In the next step of our study, we explore how the three human-caused factors mentioned above – aerosols, greenhouse gases and cloud feedback – contributed to recent low-level cloud changes.
We also look at the extent to which cloud changes could be explained by natural climate variability, which causes substantial year-to-year fluctuations in cloudiness and energy imbalance.
To do this, we use a statistical technique known as “cloud-controlling factor analysis”.
This analysis involves calculating the sensitivity of clouds to their “controlling factors”, including meteorological variables, such as temperature, humidity and winds, as well as aerosol concentrations.
To calculate how each factor contributed to the bigger picture of declining cloud cover, we combine sensitivity calculations with observed trends in meteorology and aerosol emissions.
This analysis allows us to attribute trends in cloud cover to known physical drivers: either natural climate variability, or human activities linked to aerosols, greenhouse gases and cloud feedback.
Our research finds that about 40% of the low-level cloud decrease since 2003 was driven by warming of the ocean surface – in other words, the cloud feedback process. This is followed by the effects of greenhouse gases (21%) and aerosols (14%).
Natural climate variability accounts for just 3% of the low-level cloud trend.
(The remaining 23% of the trend cannot be explained by our statistical method. This could be due to the limitations of cloud, temperature, humidity and aerosol concentration observations.)
The chart below shows how human-driven factors – the sum of aerosol effects (red), greenhouse gas emissions (pink) and cloud feedback (burgundy) – were responsible for almost three quarters of the decrease in low-level cloudiness over 2003-24. Natural climate variability (blue), on the other hand, played a minor role.
Thus, our analysis indicates that, at global scales, the observed cloud decrease is primarily driven by humans, rather than being caused by natural variations in Earth’s climate.
And, since low-level clouds contribute to half of the energy imbalance increase over the same period, it follows that a significant part of recent rises in energy imbalance can also be attributed to humans.
Clouds in climate models
So, should we be concerned that this cloudiness decrease means the Earth could see more warming than already anticipated?
To answer this, we looked at whether the climate models used by scientists to project future global warming accurately simulate recent declines in low-cloud cover.
While the models produce a wide range of outcomes, we found that, on average, the simulated changes in low-level cloudiness changes are in close agreement with real-world trends.
This is reassuring, as it means the effects of low-cloud cover are already accounted for in existing warming projections.
However, questions still remain around what is driving recent increases to the Earth’s energy imbalance, which have outpaced projections made by climate models.
Our findings rule out declines in low-level clouds as the reason that climate models have been underestimating the Earth’s energy imbalance, and, as a result, warming. But it is still possible that models are underrepresenting future global warming to some extent.
Low-level clouds are just one of several drivers of changes in energy imbalance. Future work will therefore need to assess other observed and simulated drivers of energy imbalance changes: for example, the impact of upper-level clouds, or changes in water vapour or sea ice.
Finally, it is important to stress that, while our findings are reassuring, they should certainly not make us complacent about the current global warming trend. The impacts of climate change are serious enough as they are – even if there is no evidence of a missing amplifying feedback in our projections.
The post Guest post: How declining cloudiness is accelerating global warming appeared first on Carbon Brief.
Guest post: How declining cloudiness is accelerating global warming
The United Nations Secretary-General and foreign ministers from the UK, France and Spain have blamed the deadly wildfires engulfing Europe on climate change, using the disaster to renew calls for faster cuts to greenhouse gas emissions.
António Guterres told journalists on Friday that the “climate crisis is in overdrive”, adding that global heat seen so far is just a “warm up act” as a phenomenon known as El Niño intensifies “adding fuel to a planet already on fire”.
A new World Meteorological Organisation (WMO) report published on Friday predicts that the weather pattern will grow into a “strong event” between now and October, increasing the risk of higher than normal temperatures across much of the world and disrupted rainfalls.
“That risks shattering every seasonal record – and driving even more severe effects worldwide,” Guterres said.
El Niño builds on top of an already warming world, driven primarily by the burning of fossil fuels. A WMO scientist, who did not want to be named, told journalists that all the heatwaves and other climate impacts seen so far this year are “before the effects of El Niño are really kicking in at a global scale”.
Fossil fuellling the fires
Fires have broken out across much of Europe but are threatening the most people in the south-west of France near Bordeaux and in Central Spain near Madrid. Nearly a quarter of a million people have been evacuated in France with hundreds of homes destroyed while in Spain 80,000 people have had to leave their homes and at least 13 died in one village.
A scientific study published on Friday by the World Weather Attribution group found that man-made climate change made deadly fires in France twice as likely and those in Spain twenty times more likely. Smaller fires in the UK were not analysed by the study.
UN Climate Change leader Simon Stiell blamed fossil fuels for the fires, as well as storms in Chile and heatwaves in North America and Japan in recent weeks. “The climate alarm is blaring”, he said on Wednesday.
Guterres criticised new fossil fuel production projects and fossil fuel subsidies for causing hardship across the world. Discussing his speech, a senior UN official – who did not want to be named – said the subsidies amounted to trillions of US dollars a year and criticised pension funds and institutional investors, including insurance companies, for continuing to invest in fossil fuel projects.
Asked why world leaders and the public are not prioritising climate action, Guterres said they are distracted by wars in Ukraine, the Middle East, Sudan and elsewhere and sometimes forget “other aspects that are a sometimes even more dangerous threat”.
Also the fossil fuel industry and “some countries” are campaigning to pretend that climate change does not exist, he said, adding that the UN should be more active in “naming the situations as they are and the responsibilties as they are and mobilising the public opinion”.
After meetings in Paris and Madrid earlier in the week, the UK’s new foreign minister Ed Miliband issued joint statements with his French and Spanish counterparts – Jean-Noël Barrot and José Manuel Albares Bueno – calling on the world to reduce its dependence on fossil fuels.
They promised to do more to reduce emissions and protect their people and encouraged other governments to do the same.
The UK-French statement called on governments to publish UN climate plans, known as nationally determined contributions (NDCs), which are aligned with the Paris Agreement’s goal to limit global average temperatures to 1.5C above pre-industrial levels.
According to Climate Action Tracker, only three countries – the UK, Nigeria and Norway – have submitted NDCs with 2035 emissions reduction targets which are compatible with 1.5C. Fifty-two countries – including Egypt, Vietnam and Argentina – have yet to submit an NDC at all.
Defending science
Beyond action on emissions, the ministers also intervened in an ongoing dispute over the timing of the Intergovernmental Panel on Climate Change’s (IPCC)’s next flagship assessment.
Miliband and Barrot’s statement said they “underline the importance” of scientific report feeding into governments’ next global stocktake of progress on climate action in two years’ time, calling it a “critical input” to that process.
The timing of this report has been a contentious issue in government negotiations at the IPCC and at June’s climate talks in Bonn. While a group of nations calling themselves the “friends of science” want the report before the stocktake, others like Saudi Arabia and India have argued that this would make the report of a worse quality and less inclusive of developing countries’ scientists.
Science ‘under attack’ from fossil fuel interests at UN climate talks
The UK-Spanish statement weighed in less explicitly on this issue but said that they “recall the importance of scientific evidence and acknowledge the work of the IPCC in this respect.”
The British and French ministers said they would seek to accelerate reductions of emissions in methane, a particularly potent greenhouse gas, at COP31 in November. They encouraged governments “to work jointly to develop a marketplace for fossil fuels with near-zero methane intensity.”
Methane leaks from oil, gas and coal production are a major contributor to global warming. Over a 20-year period, methane traps around 80 times more heat than carbon dioxide.
The UK and Spanish statement emphasised the importance of supporting the Global South and underlined the need to mobilise sustainable financing “at scale with the challenge we face”. The previous UK government, in which Miliband was energy minister, cut climate finance to developing countries to pay for increases in military spending.
The UK government led by new Prime Minister Andy Burnham has yet to outline any major changes to climate finance in its two weeks in power but has announced it will convert some finance from grants to loans in order to free up money to subsidise bus travel in England.
More adaptation needed
Guterres said that “it is time to stop treating each disaster as an isolated tragedy and recognise the systemic risk that is unfolding before our eyes.” A recent study found that three-quarters of UK media reports about the British June heatwave did not mention climate change.
As well as reducing emissions, the UN Secretary-General called for measures to adapt vulnerable people to extreme heat. Specifically, he said that buildings should be built and retrofitted for extreme heat and that every city and country should have heat-health action plans and early warning systems. Over 250 cities have joined the UN’s ‘beat the heat’ initiative, he said.
The Portuguese diplomat called for governments and employers to do more to protect their workers from heat, criticising global fashion brands for not setting heat standards for the factories that supply them. “No one should have to risk their life to earn a living,” he said.
The post UN chief warns climate crisis “in overdrive” as El Niño threatens to fuel the fire appeared first on Climate Home News.
UN chief warns climate crisis “in overdrive” as El Niño threatens to fuel the fire
Climate Change
‘Ride the wave of momentum’: Australia announces once-in-a-decade Marine Parks Network review
In response to the federal government announcing its once-in-a-decade review of Australia’s Marine Parks Network, the following lines can be attributed to Elle Lawless, Senior Campaigner at Greenpeace Australia Pacific:
“Greenpeace Australia Pacific welcomes today’s announcement that the Albanese Government will review Australia’s Commonwealth Marine Parks Network. This is a rare, once-in-a-decade opportunity to strengthen our marine parks and ban industrial fishing in Australia’s marine protected areas.
“Australians would be appalled to know that more than half of Australia’s Marine Parks Network currently allows for extractive industries, like longlining, bottom trawling and oil and gas mining. These so-called ‘protected’ areas were designed to safeguard our beloved ocean wildlife and underwater ecosystems – that is what Australians expect. Damaging industrial industries should not be given a free pass to trawl, fish, drill or extract from our marine parks.”
“With the first Ocean COP just around the corner, and off the back of Australia’s move to ratify the Global Ocean Treaty earlier this year, the Australian government has a unique opportunity to ride the wave of this momentum and solidify itself as a true global ocean leader.
“Greenpeace Australia Pacific is calling for industrial activities to be banned from our protected waters and for at least 30% of Australia’s ocean to be protected as ocean sanctuaries. This review presents a rare opportunity to create more ocean sanctuaries, true blue havens where ocean life can recover, thrive and repopulate the surrounding waters.”
—ENDS—
‘Ride the wave of momentum’: Australia announces once-in-a-decade Marine Parks Network review
In recent days, prominent climate sceptics and rightwing commentators have shared charts on social media incorrectly implying that Europe is having its “quietest” year for wildfires in 2026.
These include Dr Matthew Wielicki, a former University of Alabama geochemist and self-described “professor in exile”, who was recently appointed by the Trump administration to lead the US Global Change Research Program.
However, these charts paint a misleading picture as they are skewed by encompassing the entirety of Russia in the data – including the vast plains of Siberia.
These charts also use data that include fires that are deliberately lit to manage cropland, which is a declining practice across much of Europe.
In this factcheck, Carbon Brief shows that the area burned by wildfires across the European Union in 2026 is second only to 2022 for this time of year.
The latest data from the European Forest Fire Information System (EFFIS) also shows that France has set a new modern record for area burned and Spain’s wildfire season is among the worst on record.
The fires have displaced more than a third of a million people across south-western Europe, while an impending heatwave has also raised fears of the fires worsening in the coming days.
‘Quietest year’
On 27 July, as wildfires raged across multiple European countries, former Conservative peer and climate-sceptic commentator Matt Ridley posted on Twitter that “2026 is the quietest year for wildfires in Europe by some distance”.
Ridley, who sits on the academic advisory council of the Global Warming Policy Foundation (GWPF), a UK-based climate-sceptic lobby group that refuses to reveal the sources of its funding, was responding to an article by Daily Telegraph columnist Tim Stanley.
Stanley’s column, headlined: “Climate change is real – and the right needs to get serious about it”, warned:
“This is no longer a matter of speculation: the wildfires of Europe, pitiless and persistent, are the way we live now.”
Ridley included a chart from Our World In Data, showing the cumulative area burned by wildfires by week for Europe. The chart puts 2026 as having the smallest area for this time of year in a dataset going back to 2012.
Ridley’s post was widely shared by prominent rightwing figures – including Richard Tice, deputy leader of the hard-right, climate-sceptic Reform UK party, former Conservative cabinet minister Jacob Rees-Mogg and multiple commentators.
Separately, Wielicki also shared a chart on Twitter to imply that wildfires in Europe are declining. Wielicki has previously claimed that the “science is not settled on climate change”.
The charts posted by Ridley and Wielicki both use data from the Global Wildfire Information System (GWIS). The GWIS category for “Europe” encompasses all the countries on the continent and includes the whole of Russia.
As a result, Russia accounts for about 74% of the area included in the GWIS definition of “Europe”.
Wildfires in Russia typically account for 80-90% of the burned area in the GWIS Europe dataset. In 2026, fires in Russia are substantially below average. Therefore, including Russia in this comparison creates the false impression that wildfire activity across Europe is unusually low.
Dr Calum Cunningham, a research fellow at the University of Tasmania’s Fire Centre, says that such claims are “highly misleading”, noting that “they rely on aggregating fire activity across an enormous and climatically diverse region”. He tells Carbon Brief:
“A relatively quiet season in Russia can easily mask an exceptionally active season in France or Spain. If the analysis is focused on the regions actually experiencing the current fires, the picture is very different.
“The reality is that western Europe has experienced an extraordinary sequence of climate conditions this year.”
In contrast, the EFFIS provides a subset of wildfire data specifically for the area covered by the 27 nations of the EU, which, therefore, excludes Russia.
Another difference between the two datasets is that GWIS monitors all fires – including those on agricultural land that are intentionally set alight. The burned area as measured by GWIS contains significant cropland area.
By contrast, EFFIS uses land-cover data and other information to filter specifically for forest fires.
Looking at the EU-only data from EFFIS reveals that Europe is far from having its “quietest” year. The bloc’s burned area, as of 29 July, is almost 435,000 hectares (ha) – second only to 2022 for this time of year.
Notably, Wielicki has actually continued to post charts based on GWIS data, even after acknowledging that “includ[ing] all of Russia, including vast areas of Siberia…isn’t a good proxy for Europe”.
French fires
Even looking at EU-wide data misses the scale of this year’s wildfires for some individual countries.
The chart below shows the surge in burned area in France since mid-July.
For much of the first half of the year, the country was having a wildfire season that was only slightly above average in terms of total burned area. However, a notable uptick began in the first week of July.
The third week of the month saw France break its previous cumulative annual record by more than 19,000ha. That gap has widened as the fires continue to burn; as of 29 July, the cumulative burned area in France during 2026 was nearly 24,700ha above the previous record.
The fires in France follow a record-breaking June heatwave that “dried out vegetation across the region, allowing fires to spread quickly”, wrote the New York Times.
On 27 July, French president Emmanuel Macron called a “crisis cabinet meeting” in order to address the fires “ravaging several areas of south-west France”, said France 24.
More than 220,000 people have been evacuated due to the Gironde fire, west of Bordeaux, in “what may be France’s largest peacetime evacuation”, reported the Associated Press.
In the Conversation, Cunningham and two other University of Tasmania researchers write that evacuation orders “protec[t] human lives, but makes it more likely houses and other structures will burn if there’s no one to defend them”. They add:
“There is little doubt climate change has made France and Spain’s wildfires worse. They represent yet another reason to redouble our efforts to tackle climate change and stabilise our climate.”
Central Spain scorched
While Spain’s fire season has not broken records in the same way that France’s has, it is on track to be among the worst since EFFIS began reporting data in 2006.
The chart below shows the rapid increase in burned area in Spain since 8 July. The latest data from EFFIS reveal that, as of 29 July, Spain has almost matched its previous record at this point in the year. It is also nearly five times the average area burned for this time of year.
In Spain, the wildfires have been concentrated in the central part of the country, near Madrid.
BBC News reported that the fires outside the capital have burned “an area more than twice as large as the city itself”.
Nearly 90,000 people were forced from their homes in central Spain by the fires, said the Associated Press.
Pedro Sánchez, Spain’s prime minister, called the fires a “painful expression” of climate change.
Meanwhile, the UK, French and Spanish governments have issued joint statements this week in response to the fires. The UK/Spain statement begins:
“This summer’s wildfires demonstrated that climate change was now a national security emergency facing Europe and threatening our way of life.”
Related
The post Factcheck: No, Europe is not having its ‘quietest’ year for wildfires appeared first on Carbon Brief.
Factcheck: No, Europe is not having its ‘quietest’ year for wildfires
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