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
Fifty-six years after the first one rallied 20 million people across America, “we need to do things that make us feel more powerful.”
From our collaborating partner Living on Earth, public radio’s environmental news magazine, an interview by host Steve Curwood with environmental historian Adam Rome.
It was the second defeat for the Trump administration’s unusual litigation to stop states from acting on climate change.
In a setback to the Trump administration’s extraordinary legal campaign against state climate action, a federal judge threw out the Justice Department’s lawsuit seeking to prevent the state of Hawaii from suing oil companies for damages.
Judge Dismisses Trump Administration’s Bid to Block Hawaii Climate Lawsuit
Climate Change
DeBriefed 17 April 2026: Fossil-fuel power slumps | ‘Super’ El Niño warning | Afghanistan’s climate struggle
Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.
This week
Oil prices rebound
OIL UP AGAIN: Oil prices surged by more than 7% and back above $100 a barrel on Monday after US-Iran peace talks faltered and US president Donald Trump ordered the blockading of Iranian ports, reported BBC News. The jump came after prices fell last week in the wake of the announcement of a conditional two-week ceasefire, it said.
RESCUE PLANS: European countries unveiled plans to protect citizens and businesses from rising energy prices. Ireland announced a support package worth €505m, reported BBC News, while Germany agreed on measures worth €1.6bn, said Bloomberg. Meanwhile, Reuters reported on a draft EU proposal due to be unveiled next week that would see the bloc reduce electricity prices and roll out clean energy more quickly in response to the crisis.
UNSOLICITED ADVICE: Trump renewed his criticism of UK energy policy and called on the government to “drill, baby drill”, reported the Independent. Via social media, the president said: “Europe is desperate for energy, and yet the United Kingdom refuses to open North Sea oil, one of the greatest fields in the world. Tragic!!!” (See Carbon Brief’s recent factcheck of various false claims about the North Sea.)
Around the world
- C-WORD: Faced with pressure from the US, countries attending spring meetings of the International Monetary Fund and World Bank were urged to “not mention the climate”, reported the Guardian. It added that plans to agree a new “climate change action plan” for the World Bank “may be shelved, along with substantive discussion of the climate crisis”.
- NEW DIRECTION: Péter Magyar’s landslide victory over Victor Orbán in Hungary’s elections “presents new opportunities for the country to reduce emissions and invest in clean energy”, reported Time. Carbon Brief explored what it means for European climate action.
- ‘FURNACE’ SUMMER: There was widespread coverage – including in the Boston Globe, ABC News, CNN, Euro Weekly News, Guardian and New Scientist – of warnings from meteorologists of the development of a “super” El Niño phenomenon that could ramp up temperatures and drive extreme weather.
- ANTALYA COP: The Turkish government unveiled the dates and venues for the “leaders’ summit” segment of November’s COP31 conference, according to Climate Home News.
- PACIFIC PRE-COP: Meanwhile, the Guardian reported that Tuvalu will host a special meeting of world leaders before the climate summit in Antalya.
€10bn a year
The amount of state support that French prime minister Sébastien Lecornu has pledged for electrification through to 2030 in a bid to reduce the country’s dependence on fossil fuels. In a speech late on Friday 10 April, Lecornu noted the figure amounted to a “doubling” of existing support.
Latest climate research
- Over a four-month period of 2023, more than 70% of editorials discussing net-zero in four right-leaning UK newspapers included “at least one misleading statement” | Climate Policy
- Air pollution from global transport currently has a net cooling effect that offsets 80% of the warming impact of the sector’s CO2 emissions | npj Climate and Atmospheric Science
- The incorporation of “observational constraints” into climate-model projections suggests that the Atlantic Meridional Overturning Circulation could weaken by 50% by 2100 in a medium-emissions scenario | Science Advances
(For more, see Carbon Brief’s in-depth daily summaries of the top climate news stories on Monday, Tuesday, Wednesday, Thursday and Friday.)
Captured
Analysis by the Centre for Research on Energy and Clean Air (CREA) found that global electricity generation from fossil fuels fell in the first month of the closure of the Strait of Hormuz. Across all countries with real-time electricity data outside of China, coal-fired power generation fell 3.5% and gas-fired power generation fell 4.0%, according to CREA. This was offset by a rise in solar power and wind generation, which increased by 14% and 8%, respectively. Hydropower generation also saw a small increase, the analysis showed, but this was “more than offset” by a drop in nuclear power generation.
Spotlight
How climate change affects Afghan lives
This week, Carbon Brief reports on the impact of climate change in Afghanistan, following deadly floods this year.
Earlier this month, heavy rains, flash floods and landslides struck large parts of Afghanistan, damaging thousands of homes, destroying crops, bridges and roads and taking nearly 100 lives.
The flooding – reported to have affected 74,000 people in 31 of 34 provinces – is the latest weather-related catastrophe to afflict the nation, whose communities have suffered the brunt of repeated flash floods, droughts and landslides in recent years.
Hameed Hakimi, non-resident senior fellow at the Atlantic Council’s South Asia Center, told Carbon Brief the recent floods would hurt livelihoods and food security, noting reports of destroyed wheat and rice crops in the most affected eastern parts of the country. He said:
“This is common. For at least a decade now, [we have seen] these flash floodings and the damage that happens to rural life, farming, the disruption to crops…Flash flooding physically eats up the land. So, it not only damages where people live, but also people’s livelihoods, based on what they grow.”
The damage to crops will be felt acutely, he explained, given that food security in the landlocked nation is already strained by the blockage of its main transit trade artery through Pakistan and international sanctions that have frozen long-term development aid.
Speaking to Carbon Brief, Abdulhadi Achakzai, founding CEO of the Environmental Protection Trainings and Development Organization (EPTDO), an Afghan NGO, described flooding in Afghanistan as a “chronic situation”.
Achakzai, whose organisation runs projects that help urban and rural communities adapt to climate impacts, says climate change hurts the country in four key ways: extreme drought; extreme temperature; “natural hazards”, including landslides and dust storms; and, finally, flash flooding. He said:
“Climate change is a serious matter in Afghanistan. Every nation and every corner within this country is severely affected.”
Ranked 176 of 187 on the University of Notre Dame “global adaptation index”, Afghanistan is among the countries most vulnerable to climate change.
Average temperature across the country has increased from 12.2C in 1960 to 14.2C in 2024, according to the World Bank’s climate change knowledge portal. Drought is widespread, severe and persistent – harming food and water security in a nation of subsistence farmers.
Meanwhile, extreme weather events are the leading driver of internal displacement in the country. More than three-quarters of the 710,000 people who relocated within Afghanistan in 2024 did so driven by “environmental hazards”, such as drought and flood, according to a recent climate vulnerability assessment from the International Organization for Migration.
Finance struggles
Despite feeling the impacts of extreme weather, Afghanistan has been barred from UN climate negotiations and had limited access to climate finance since 2021. (The government attended COP29 in Baku as guests of the Azerbaijan hosts, but did not take part in formal negotiations.)
This is because the international community does not recognise the Taliban government, which resumed power in 2021, due to its record on human rights and its repression of women and girls in particular.
Almost all financing from key climate funds has been suspended, with the exception of a few projects where UN agencies and NGOs act simultaneously as a “requesting” and “implementation” partner.
Aid from UN climate funds fell from $5.9m annually over 2014-20 to $3.9m annually over 2021-24, according to recent analysis by the Berghof Foundation. Multilateral development banks provided a further $337m of funds badged as “climate finance” over 2021-23, it said.
By comparison, Afghanistan’s national climate plan, submitted to the UN Framework Convention on Climate Change (UNFCCC) in 2016, requested $17.4bn in climate finance over 2020-30. An updated national climate plan seen by Carbon Brief – completed in 2021 and later endorsed by the Taliban government, but not accepted by member governments of the UNFCCC – called for $20.6bn through to 2030.
Achakzai, whose organisation attends the COP climate summit each year in an observer capacity, has in the past been the sole delegate from Afghanistan to the conference.
He is calling on the UNFCCC to accept the country’s latest climate plan – and to find an “alternative solution” that would give the people of the country a voice in negotiations. He said:
“Every year we are losing hundreds, thousands of people because of climate change-related matters. Every year we are losing hundreds, thousands of hectares of crops. We are affected by [the decisions of] other countries. Why are we not part of this process?”
Watch, read, listen
BLOSSOM WATCHER: The Guardian reported on the successful search to find a researcher to continue Japan’s 1,200-year cherry blossom record.
COP OUT: Deutsche Welle spoke to experts to understand why India walked away from its bid to host COP33 in 2028.
‘BOMBS AND PORN’: The New Republic looked at who is set to benefit from the rapid build-out of energy-intensive AI datacentres.
Coming up
- 20-24 April: Intergovernmental Panel on Climate Change (IPCC) working group one report author meeting, Santiago, Chile
- 22 April: Earth day
- 22 April: Launch of third edition of the Lancet Countdown’s Europe report
- 24-29 April: First conference on transitioning away from fossil fuels, Santa Marta, Colombia
Pick of the jobs
- International Organization for Migration, senior thematic associate (climate action) | Salary: UN G-6 salary grade | Location: Dakar, Senegal
- Climate Action Network UK, several board member roles | Salary: Unknown. Location: Unknown
- UK Department for Energy, Food and Rural Affairs, G7 science lead | Salary: £56,375. Location: Bristol, London, Newcastle-upon-Tyne or York, UK
- Save the Children UK, senior climate change advisor | Salary: £62,000-£65,000. Location: London
DeBriefed is edited by Daisy Dunne. Please send any tips or feedback to debriefed@carbonbrief.org.
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The post DeBriefed 17 April 2026: Fossil-fuel power slumps | ‘Super’ El Niño warning | Afghanistan’s climate struggle appeared first on Carbon Brief.
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