Global and Regional Climate Change: Underlying Science and Emerging Riddles

Global and Regional Climate Change: Underlying Science and Emerging Riddles
May 02, 2008

Veerabhadran Ramanathan
Distinguished Professor of Climate and Atmospheric Sciences, University of California, San Diego

Ramanathan deploys simple but extremely helpful metaphors to describe the processes behind warming. CO2 in the atmosphere, whether manmade or natural, surrounds the earth like a blanket, holding onto the radiation from the sun. When the blanket is behaving properly, enough sun's heat stays on earth to keep biological forces humming, and the rest escapes back into space. But if this blanket gets thicker, it "prevents the body from losing heat." CO2 is particularly noxious, since it "lives in the atmosphere for a century if not longer." But it turns out we have other molecules circling the globe to worry about. 

Starting in the 1970s, scientists discovered that compounds in the atmosphere, such as chlorofluorocarbons and methane, acted more powerfully than CO2 in making our "blanket" more efficient in trapping heat. They began developing models trying to describe the complex interplay of heat"trapping gases with earth's natural climate systems. Ramanathan's work, which involves precise observations from the surface, satellite measurements, balloons and unmanned vehicles, has convinced him "that climate change is worse than what we get from the models." 

The most recent UN report on climate change predicts that greenhouse gases already in circulation have committed the planet to a warming of 2.5 degrees. "No matter what we do today to reduce emissions, the planet will still heat up," says Ramanathan. But, through a quirk that Ramanathan has spent 10 years uncovering, the planet actually manifests only of the warming it should based on these climate models. Air pollution, specifically brown clouds from burning biomass, Ramanathan has learned, act as a global warming mask, reducing sunlight on the ground. "On the one hand, it has protected us, but also prevented us from seeing the full blast of the greenhouse effect," he says. "One of the dumbest things we can do is to reduce sunlight," because it reduces ocean evaporation, which cuts down on rainfall, and shifts weather systems everywhere, shrinking harvests and glaciers. 

We are left with "Faustian bargains," says Ramanathan. If we cut airborne pollutants such as sulfur, the mask will drop, temperatures rise rapidly, and climate tipping elements come into play. Curing one ill causes another. Any plan for "dismantling the experiment we have done with blankets, mirrors and dust must be done as carefully as dismantling a nuclear device."

About the Speaker(s): Veerabhadran Ramanathan discovered the greenhouse effect of CFCs and numerous other manmade trace gases in the 1970s. He correctly forecast in 1980, along with R. Madden, that the global warming due to carbon dioxide would be detectable by the year 2000. He has worked with NASA to demonstrate the cooling effect of clouds on the planet, and the impacts of 'brown' clouds and greenhouse gases on rainfall,harvests of different types of crops, and the melting of glaciers.

Ramanathan currently chairs the UNEP-sponsored ABC Project with science team members from the USA, Europe, India, China, Japan, Korea and other Asian countries. He is the recipient of the American Meteorological Society's Rossby medal. He is a member of the American Philosophical Society, the National Academy of Sciences, the Academia Europea and the Third World Academy of Sciences. He currently chairs the US National Academy of Sciences panel that provides strategic advice to the US Climate Change Science Program (CCSP) which is a $2 billion/year inter-agency research program on climate change. 

Ramanathan has published over 175 peer-reviewed articles in major journals. He is part of the Nobel Peace prize (2007) winning Intergovernmental Panel on Climate Change since its inception, and for the 2007 report served as one of the lead editors in IPCC-AR4 (2007), WG-I. He received his undergraduate and graduate education in India and earned his Ph. D. in planetary atmospheres from the State University of New York at Stony Brook.
Host(s): School of Science, Center for Global Change Science

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