Climate change could cause low level clouds over oceans to disappear

Low hanging stratocumulus clouds | Flickr

Low hanging stratocumulus clouds | Flickr

Stratocumulus clouds spread out like puffy cotton balls in orderly rows above the ocean in the sub-tropics.

Clouds now cover about two-thirds of the planet at any moment. They're not as elegant as cirrus clouds (those horsetail wisps high in the sky) or as majestic as cumulonimbus clouds (big, scary thunderheads).

The clouds cover about 20% of subtropical oceans and play an important role in reflecting sunlight back into space.

According to one landmark report, countries have just eleven years until the world enters an irreversible state of climate change. Instead, current global climate models approximate the impact of these cloud formations using related variables like temperature and humidity.

The findings were published in Nature Geoscience.

According to the new study led by researchers at California Institute of Technology, CO2 concentrations higher than 1,200 parts per million (ppm) could push Earth to a tipping point in which marine stratus clouds become unstable.

Rising greenhouse gases in Earth's atmosphere could eventually drive low-level clouds out of the skies.

"It's a dramatic effect", Schneider told The Washington Post. The researchers also found that once the cloud decks vanished, they did not reappear until Carbon dioxide levels dropped to levels substantially below where the instability first occurred. At our current rate of emissions, we'll hit that tipping point in about 100 years.

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Climate scientists have always been confounded by clouds.

And, once they are gone, stratocumulus clouds may never take shape again. They are remarkably insubstantial elements of the natural world.

At present, the level of Carbon dioxide in the atmosphere is around 410 ppm. Increasing levels of this greenhouse gas are largely blamed for climate change. During the next century, the Carbon dioxide level of the Earth could rise above 1,200 ppm. However, if rising Carbon dioxide led to the loss of stratocumulus clouds, that could explain the unusual heat spike. "But it's not outside the realm of the possible", Schneider said. "But our results show that there are risky climate change thresholds that we had been unaware of".

But Huber noted that the Schneider paper offers a potential answer to a long-standing riddle. See a brief epoch from 55 million years ago called the Paleocene-Eocene Thermal Maximum. That's the famous "crocodiles in the Arctic" period. They observed instability of the cloud decks followed by a spike in warming when Carbon dioxide levels exceeded 1,200 ppm. And this is with quite a bit of cloud cover overhead.

Stratocumulus clouds are produced as warm air rises from the surface and cools, causing water vapor to condense. This occurs at a physical scale that traditional climate models can not easily capture.

Clouds have mostly "fallen through the computational cracks", said Schneider. He and his colleagues have developed a new model that uses what is known as a large eddy simulation.

When the planet got hot, it got really hot.

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