Shrinking cloud cover adds to accelerating Climate Crisis

Earth’s cloud cover is diminishing in key regions, reducing the planet’s ability to reflect sunlight back into space and adding to the accelerating Climate Crisis, research reported by Science found.

As bne IntelliNews reported, shrinking cloud cover is reflecting less sunlight from the and adding to the warming effect of Green House Gases (GHGs). Currently global warming is happening faster than all the 30-plus climate models used by the Paris Agreement to determine the rates of reduction of emissions. The United Nations’ Intergovernmental Panel on Climate Change (IPCC) says the 1.5°C – 2.0°C targets have already been missed and the world is on course to warm by 2.7°C-3.2°C in the coming decades.

Decreasing cloud cover with only bring that end point closer. Satellite observations and climate analyses suggest that low-lying marine clouds — particularly over subtropical oceans — have declined in recent decades, weakening what scientists describe as a critical planetary cooling mechanism. Because such clouds act as a mirror, reflecting incoming solar radiation, even small reductions can produce measurable warming effects.

The shrinking cloud cover is added to the earth’s energy imbalance (EEI) which is acting on top of the greenhouse effect of emitted gases like CO₂ and methane. More energy than ever before is coming into the planet (absorbed sunlight) than is going out (heat radiated to space), said the scientists. The earth’s energy imbalance (EEI) has escalated in the past decade, they said. The imbalance so far in the 2020s is almost double the rate during the study’s calibration period, from mid-2005 to mid-2015.

The findings come as global temperatures have repeatedly broken records, with the last three years being the hottest year in documented history. Researchers say the loss of reflective cloud cover may be helping to explain why temperatures are rising faster than the models predicted.

Scientists cited by Science report that changes are especially evident in stratocumulus cloud decks over the Pacific and Atlantic oceans. These bright, persistent cloud formations have historically offset a portion of greenhouse gas-driven warming. Their retreat means more heat is absorbed by darker ocean waters.

The causes remain under investigation. One hypothesis links the trend to cleaner shipping fuels. Regulations introduced by the International Maritime Organization in 2020 reduced sulphur emissions (SO₂) from marine fuel, cutting aerosol pollution that can seed cloud formation and increase cloud brightness. With fewer aerosols available, clouds may form less readily or reflect less sunlight.

Other researchers point to feedback loops within the climate system. As oceans warm, atmospheric circulation patterns can shift, thinning cloud layers and reinforcing additional warming. This self-reinforcing cycle is a longstanding concern in climate science because it could accelerate temperature rises beyond earlier expectations.

Clouds remain one of the biggest sources of uncertainty in climate modelling as they are not well understood, and small variations in their behaviour can alter projections of future warming by tenths of a degree Celsius or more. A sustained reduction in low-cloud cover would effectively increase the Earth’s climate sensitivity to greenhouse gas concentrations.

While further study is required to determine whether the recent decline represents a long-term shift or natural variability, researchers warn that the trend highlights the complexity of efforts to curb warming, as reductions in air pollution can produce unintended climatic side effects even as they deliver clear public health benefits.