Clouds are shrinking and making the Earth hotter

Clouds help cool the Earth by reflecting sunlight. But now, storm cloud zones are shrinking. This shrinkage is letting in more solar radiation.

A new study, led by NASA and including Monash researchers, shows that this is the biggest reason for Earth’s recent heat rise. The study appears in the journal Geophysical Research Letters.

Storm cloud zones in the tropics and midlatitudes have contracted by 1.5% to 3% per decade. These zones used to reflect a lot of sunlight back into space. Their disappearance is allowing more heat to reach the surface.

Shrinking clouds let earth absorb more heat

Christian Jakob, a professor at Monash University, noted that this finding clarifies how much extra solar energy Earth now absorbs. “We’ve long known that changes in atmospheric circulation are affecting clouds,” he said.

“For the first time, we now have research showing those shifts are already driving major changes in how much energy the Earth absorbs.”

This research helps explain the heat anomalies of recent years, including the extreme warmth of 2023.

Satellite clues from decades of data

The experts used satellite data from 2001 to 2023. They measured two cloud features: total cloud cover (TCC) and shortwave cloud radiative effect (SWCRE). SWCRE measures how much sunlight clouds bounce back.

A more negative number means more sunlight is being reflected. But scientists found that zones of strong SWCRE are shrinking.

In high latitudes, these zones contracted by up to 1.32% per decade. In the tropics, the Intertropical Convergence Zone (ITCZ) narrowed. Stratocumulus cloud regions also shrank.

From cloud retreat to heat gain

The result of all this: more warming. The total increase in absorbed solar energy was about 0.45 W/m² per decade. Of this, 0.37 W/m² comes from the shrinking cloud zones.

The changes were strongest in high-latitude storm tracks and the tropical ITCZ. Even small reductions in cloudy area had large effects on Earth’s heat budget.

The study shows most warming came from cloud area loss, not changes within the clouds themselves.

Winds make storm clouds shrink

Why are storm clouds shrinking? It’s mostly due to global wind pattern changes. The Hadley cell is widening. Jet streams are shifting toward the poles. The ITCZ is narrowing. These trends match what climate models predict for a warming planet.

The researchers also found that high-latitude storm clouds are retreating because of the warming-driven shift in jet streams. This creates fewer clouds in key cooling zones.

“It’s an important piece in the puzzle of understanding the extraordinary recent warming we observed, and a wake-up call for urgent climate action,” Jakob notes.

Local factors also shrink clouds

Besides circulation shifts, cloud changes also arise from local factors. These include fewer aerosols from ships, which once helped clouds reflect more sunlight.

Changes in cloud types and altitudes also matter. In the tropics, these effects added 0.21 W/m² per decade to the warming.

In contrast, polar regions showed some minor cooling due to increased cloud reflection in cold clouds. But the big picture is clear: cloud zone shrinkage is doing most of the damage.

Global cooperation and local weather shifts

Professor Jakob warned about the dangers of reducing science funding. “If you want to understand the climate crisis, and prepare for its impacts, you need this kind of data and this kind of analysis,” he said.

Jakob urged a shift in focus – from climate change averages to daily weather impacts. “Our mission is to understand how Australia and the world’s weather is being reshaped by a warming climate,” he said.

“Our goal is to provide the knowledge and tools needed to help governments, businesses and communities prepare for what lies ahead.”

Clouds are changing fast

Earth is losing some of its protective cloud shield. The shrinking of storm cloud zones is now the top driver of increased solar heat absorption.

This change isn’t gradual. It’s already happening. And it’s amplifying warming faster than expected.

That means climate action must respond not only to emissions, but also to how weather patterns are shifting around the globe.

The study is published in the journal Geophysical Research Letters.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–