Global warming imperils clouds that shelter Earth

PARIS: Marine clouds that protect us from hothouse Earth conditions by reflecting sunlight back into space could break up and vanish if CO2 in the atmosphere triples, researchers warned.

“Our results show that there are dangerous climate change thresholds of which we were unaware,” Tapio Schneider, a scientist at the Jet Propulsion Laboratory in Pasadena, California and lead author of a study detailing the findings, said on Monday.

So-called stratocumulus clouds cover about 20% of subtropical oceans, mostly near western seaboards such as the coasts of California, Mexico and Peru. “When they disappear, Earth

8° warms dramatically, by about C – in addition to the global warming that comes from enhanced greenhouse concentrations alone,” according to the study.

A temperature increase of that magnitude would melt polar ice and lift sea levels tens of metres.

The last time the planet was that hot, some 50 million years ago during the Eocene Epoch, crocodiles roamed the Arctic.

Even half that much warming would overwhelm humanity’s capacity to adapt, scientists say.

1°

A barely C increase since the mid-19th century has been enough to worsen heatwaves, droughts and flooding, along with cyclones engorged by rising seas.

The 2015 Paris climate treaty enjoins nations to cap the rise in

2° temperatures at “well below” C.

A major UN report published in October, however, showed that

2° even a C hike over the pre-industrial benchmark will have dire impacts, such as the demise of shallow-water coral reefs that sustain a quarter of marine biodiversity.

Since man-made global warming began, CO2 concentration in the air has gone up nearly 45%, from 285 to 410 parts per million (ppm).

Using an innovative approach to modelling the behaviour of the stratus clouds, Schneider and his colleagues calculated that protective cloud cover could break up if CO2 levels reached 1200 ppm, though the “tipping point” might be higher.

Passing that threshold may not be as far-fetched, scientists caution.

Even after 30 years of warnings about the consequences of climate change, global greenhouse gas emissions are still climbing year-on-year.

At current rates of CO2 pollution – known as the “business as usual” scenario – “the 1200 ppm value will be crossed by 2104”, Malte Meinshausen, director of the Climate and Energy College at the University of Melbourne, said.