PASADENA, Calif. (CN) – Low-level stratus clouds that cool Earth’s oceans could disappear if carbon dioxide keeps building up in the atmosphere – a scenario that could trigger a spike in global warming, researchers from the California Institute of Technology said Monday.
Carbon dioxide is a colorless heat-trapping greenhouse gas released through human activities, such as deforestation and burning fossil fuels, and naturally through respiration and volcanic eruptions.
If fossil fuels continue to be burned at the current rate, Earth's CO2 level could surpass 1,200 parts per million in the next century, Caltech researchers said in a study published Monday in Nature Geoscience.
Stratus clouds, which cover 20 percent of subtropical oceans and are prevalent off western coastlines such as in California and Peru, could destabilize and eventually disappear at that level of CO2 concentration.
The clouds – which meteorologists often call “the marine layer” – play a critical role in regulating global temperature since they cool and shade the earth by reflecting sunlight back into space.
Caltech researchers’ climate model found concentrations of carbon dioxide above the current 410 parts per million could trigger a spike in global surface temperatures of 14 degrees Fahrenheit.
"I think and hope that technological changes will slow carbon emissions so that we do not actually reach such high CO2 concentrations,” Caltech's Tapio Schneider said in a statement. “But our results show that there are dangerous climate change thresholds that we had been unaware of."
Schneider and his co-authors, Colleen Kaul and Kyle Pressel of the Pacific Northwest National Laboratory, estimated the spike in global temperatures by creating a small-scale model of a section of the atmosphere above a subtropical ocean.
The researchers also found that once the stratus cloud decks vanished, they did not reappear over the oceans until CO2 levels dropped to levels substantially below where the instability of the clouds first occurred.
Schneider said the research could shed light on a “blind spot in climate modeling” that has confounded scientists for years.
Geological records indicate that during the planet’s Eocene period around 50 million years ago, the Arctic had no frost covering and was hot enough to host crocodiles. The Caltech team believes CO2 concentrations would need to reach 4,000 parts per million for the Arctic to be that warm, and that the loss of stratus clouds could explain the appearance of the Eocene’s hothouse climate.
Schneider said in the statement that he is developing a new climate model that can more accurately determine the CO2 level at which the instability of the cloud decks occurs.
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