Clouds Provide Clue to Better Climate Predictions

A research group from the CERN Cloud experiment, including scientists from Carnegie Mellon University's College of Engineering and Mellon College of Science , have uncovered the processes behind the formation and evolution of small atmospheric particles free from the influence of pollution. Their findings are key to creating accurate models to understand and predict global climate change. Clouds and aerosols - small airborne particles that can become the seeds upon which clouds form - are essential to climate predictions because they reflect sunlight back into space. Reflecting light away from Earth can have a cooling effect, masking some of the warming caused by greenhouse gases. "The best estimate is that about one-third of the warming by greenhouse gas emissions is masked by this aerosol cooling, but the fraction could be as large as half and as little as almost nothing,” said Neil Donahue, professor of chemistry , chemical engineering , engineering and public policy, and director of CMU's Steinbrenner Institute for Environmental Education and Research. In order to have complete climate prediction models, scientists need to incorporate clouds and aerosols into their calculations, but understanding how new aerosol particles form and grow in the atmosphere, and how they affect clouds and climate, has been challenging. Scientists involved with CERN's CLOUD experiment study use a large chamber to simulate the atmosphere and track the formation and growth of aerosol particles and the clouds they seed.