At high enough atmospheric carbon dioxide (CO2) concentrations, Earth could reach a tipping point where marine stratus clouds become unstable and disappear, triggering a spike in global warming, according to a new modeling study.
This event—which could raise surface temperatures by about 8 Kelvin (14 degrees Fahrenheit) globally—may occur at CO2 concentrations above 1,200 parts per million (ppm), according to the study, which was published in Nature Geoscience on February 25. For reference, the current concentration is around 410 ppm and rising. If the world continues burning fossil fuels at the current rate, Earth's CO2 level could rise above 1,200 ppm in the next century.
"I think and hope that technological changes will slow carbon emissions so that we do not actually reach such high CO2 concentrations. But our results show that there are dangerous climate change thresholds that we had been unaware of," says Caltech's Tapio Schneider, Theodore Y. Wu Professor of Environmental Science and Engineering and senior research scientist at the Jet Propulsion Laboratory, which Caltech manages for NASA. Schneider, the lead author of the study, notes that the 1,200-ppm threshold is a rough estimate rather than a firm number.
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