Climate change may break up clouds, cause worst-case warming
Unchecked emissions could lead to drastic decline in stratocumulus clouds, triggering a nightmare scenario of global warming
Stratocumulus clouds, the most common cloud type in the world, aren't just pretty to look at. Just by existing, they help regulate our planet's climate.
They cover 20 per cent of the world's oceans in the lower latitudes, and stratocumulus clouds that form there reflect as much as 30 per cent of the sun's rays. But if carbon emissions continue apace, their numbers are set for a drastic decline, triggering a nightmare scenario of global warming.
That's according to a new paper published in Nature Geoscience, which takes a look at what would happen to Earth's cloud cover, and temperature, with atmospheric carbon dioxide at 1,200 ppm, about three times the current level.
The result, according to the scientists' simulations, is a breakup of stratocumulus cloud cover. Without that reflective expanse, global temperatures could shoot up by around eight degrees on average, and 10 degrees in the subtropics.
“This is a warning shot about the future,” study co-author Tapio Schneider, of the California Institute of Technology in Pasadena, said in an interview with Nature.com. “If we do not reduce emissions, very large and difficult-to-reverse climate changes are possible.”
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The study makes clear those kinds of runaway CO2 levels aren't imminent, gradually ramping up over 100-150 years, and that's if governments don't follow through on their emissions reductions targets.
Presently, an increase of even 2°C in global average temperatures relative to pre-industrial levels is considered such a concern, that 2015's Paris Agreement pledged to keep temperature rises "well below" that benchmark.
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Even that small increase already will have a serious impact on Earth's climate, including more frequent, and more severe, extreme weather episodes. A rise of eight degrees, by comparison, would be so drastic, it would take global temperatures to levels not seen in 56 million years.
That period, known as the Paleocene-Eocene Thermal Maximum, was marked by a dramatic drop in ocean plankton levels as the seas became hotter and more acidic, according to Quanta Magazine.
Writing in Quanta, Natalie Wolchover describes it thus:
"The ocean turned jacuzzi-hot near the equator and experienced mass extinctions worldwide. On land, primitive monkeys, horses and other early mammals marched northward, following vegetation to higher latitudes. The mammals also miniaturized over generations, as leaves became less nutritious in the carbonaceous air. Violent storms ravaged the planet; the geologic record indicates flash floods and protracted droughts."
Once these crucial stratocumulus cloud banks have broken up, the researchers say they can only reform once emissions have dropped "substantially below" the CO2 concentrations that triggered their distintegration.
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SOURCES: Nature Geoscience | Nature.com | Quanta
