Global cloud coverage appears to be shrinking and could be exacerbating the warming effects of climate change, according to research based on NASA satellite data.

Earth currently receives more solar energy than it loses. However, although it explains a lot of it, our dependence on fossil fuels is not enough to explain the total extent of these changes. Neither is the albedo effect – the phenomenon whereby declining levels of ice coverage decrease the amount of sunlight reflected by the Earth and increase the amount being absorbed.

In a study published August, climate scientist at NASA’s Goddard Institute for Space Studies George Tselioudis and co-authors examined satellite datasets covering two periods of time: the first from 1984 to 2018 and the second from 2000 to 2018. 

One significant change they noted occurred in the intertropical convergence zone (ITCZ) – aka the low pressure region near the Earth’s equator where the northeast and southeast trade winds meet. Typically, heavy clouds form in this particular part of the world as warm air rises and is replaced by cooler air. According to the results, the zone has narrowed, resulting in lower cloud cover. 

In contrast, the subtropical dry zone has expanded. Taken together, these changes have resulted in lower levels of global cloud coverage. The amount of cloud shrinkage varies by dataset and period, but seems to occur at a rate between 0.72 percent and 0.17 percent a decade. 

Referring to the link between global warming and lower cloud coverage, Tselioudis told Science: “I’m confident it’s a missing piece. It’s the missing piece.”

Tselioudis et al's latest research – presented at a meeting of the American Geophysical Union on December 11 – examines data from NASA’s Terra satellite over the last 22 years. It appears to confirm the results of the previous study, reportedly finding that cloud coverage was falling by around 1.5 percent every decade, suggesting cloud cover is decreasing and that the changes are contributing to higher levels of warming. While these might not appear like significant numbers, it indicates “a cloud feedback that’s off the charts” Bjorn Stevens, a climate scientist at the Max Planck Institute for Meteorology, told Science.

It remains to be seen whether these trends will continue and the impact they will have on overall warming trends. However, it goes to show just how complex Earth’s climate systems are. 

The August study is published in the journal Climate Dynamics, and the latest research was presented at AGU24.

[H/T: Science]