Scientists know that global warming is changing clouds, but they haven’t been sure whether those changes would heat or cool the planet overall.
It’s an important question, because clouds have been the main source of uncertainty in projecting just how sensitive the climate is to increasing greenhouse gas concentrations, and because clouds have a huge effect on the climate system. Just a 20 percent change in their extent or reflectivity would have more of an impact than all the greenhouse gases released by human activities.
A new study published today in the Proceedings of the National Academy of Sciences may help find an answer. The researchers analyzed 20 years of cloud data from satellites and found that it was 97.5 percent certain that changes in clouds brought about by climate change will amplify warming.
Since the cloud effect has been uncertain, its accurate measurement also helps affirm other recent projections that a doubling of carbon dioxide in the atmosphere will warm the planet’s surface by about 5.8 degrees Fahrenheit, said said co-author Paulo Ceppi, a climate scientist with the Grantham Research Institute on Climate Change at Imperial College London. [Continue reading…]