Could clouds’ radiator effect vanish with global warming?

A new study published in the journal Nature Geoscience has concluded that if the world adopts a business-as-usual approach towards global emissions, then stratocumulus clouds, which provide a cooling effect in the poles and subtropics, could break up, subjecting the world to even greater warming.

The research was carried out by Tapio Schneider, who studies cloud dynamics at the California Institute of Technology in Pasadena, United States. The results were published on February 25, 2019.

“The clouds that clump together into massive sheets over the oceans are called stratocumulus clouds, and worldwide, they can reflect roughly 4 to 7 per cent of the energy from the Sun,” reads a web report on the website of Nature.

As part of the study, Schneider and his team created a computer simulation where they increased current carbon dioxide levels from 400 parts per million (ppm) to more than 1,200 ppm.

When they did this, the atmosphere warmed up and dense layers of stratocumulus cloud, which need to radiate heat into the upper atmosphere to maintain themselves, started to break into smaller, puffier clouds, which eventually dispersed.                          

The researchers noted that a world with fewer clouds could witness up to 8ºC of warming in addition to that caused by greenhouse gases. They estimate that the transition from 400 ppm to 1,200 could happen over the next 100 years.

However, retired scientist from the Indian Institute of Tropical Meteorology, Pune, JR Kulkarni, told Down To Earth that the study was not convincing enough.

“The figure of 1,200 ppm is very high. A transition from 400 to 1,200 is highly unlikely, if not impossible,” said Kulkarni.

He pointed out other problems. “The role of clouds in predicting climate change is still very uncertain. Clouds reflect the sun’s energy as well as suck radiation from the surface of the earth. In other words, they have both, a greenhouse effect as well as a cooling one. That is why most climate models are imperfect, for the moment,” Kulkarni said.

However, Kulkarni believes climate prediction models will get more accurate in the years to come.

“Currently, we use satellite-derived vertical profiles of green house gas data in the climate models which are not very accurate,” he said. “What needs to be done is vertical measurement of gases from the surface to a few kilometres into the air,” he added.

In the coming years, said Kulkarni, observations made from balloons and aircraft will validate the satellite data. “That is when we would be able to believe such models. For now, we can’t conclude anything,” he said.  

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