Study finds increasing carbon dioxide levels threaten marine stratus clouds

One look at the image of the Golden Gate Bridge below and most of us would call the clouds "fog." What we see there is a marine layer cloud, and a new study has been published that says high carbon dioxide levels could destabilize this type of cloud. The study notes that Earth could reach a tipping point that would make marine layer clouds unstable and disappear.

If clouds of this sort did disappear, according to the study, the surface temperatures around the planet could increase by about 14-degrees Fahrenheit. This tipping point is said to be about 1,200 parts per million (ppm). The current concentration of carbon dioxide in the atmosphere is 410 ppm.

The study did help solve a mystery in paleoclimatology. Geological records indicate that about 50 million years ago, the Arctic was ice-free and crocodiles lived there. Current climate models predict that to melt the Arctic would require carbon dioxide levels of 4,000 ppm. The catch is that level is more than twice as high as what was thought to exist in the atmosphere at the time.

Scientists think that the additional warming could be attributed to the loss of stratus cloud decks. Stratus clouds are said to cover about 20% of subtropical oceans, particularly in the eastern portions of the oceans such off the coast of California or Peru. Those clouds shade the Earth and reflect sunlight that would usually heat the Earth.

In an experiment, the researchers created a small-scale model that represented an atmosphere above a subtropical ocean and simulated the clouds over the patch of the ocean using supercomputers. Instability of cloud decks led to a spike in warning after carbon dioxide levels hit 1,200 ppm. After the cloud decks disappeared, they didn't return until carbon dioxide levels reached substantially lower than the levels that existed before they disappeared according to the scientists.