ogram. Caldeira sets the stage for the long-term consequences of continued CO₂ emissions based on the physics and chemistry of ecological systems, analysis of Earth's history, and sophisticated climate modeling. He begins with a brief history of carbon-cycle science: In the 19th century, scientists found that the greenhouse gas CO₂ could explain why the Earth is not a frozen planet. The gas produces an insulating blanket, which acts like a greenhouse. Some scientists suspected that CO₂ played a role in the waxing and waning of the ice ages. Since that time, researchers have developed a much better understanding of the carbon cycle, but the basic science underlying the importance of CO₂ for the Earth has been established for over a century.

Caldeira addresses the carbon budget--the amount of carbon released to the atmosphere minus that which is locked-up by terrestrial plants as they use carbon for photosynthesis or is absorbed by the oceans. Some of the ocean carbon is used to make skeletons and shells. It is possible that about half of the predicted emissions could be sequestered this way.

According to Caldeira, however, the net result of continuing current trends could yield an atmosphere with about five times more CO₂ than would have occurred without human-made emissions.

He states that if the planet were to warm by only 3.6 degrees F per century, as suggested by some models, the snow and ice in latitudes near the poles would melt and higher temperature bands would "march poleward" by more than 30 feet (10 meters) per day, affecting everything in the wake. If CO₂ from fossil-fuel resources is ultimately released to the atmosphere, the Antarctic and Arctic ice sheets would be at risk of melting, which would cause a rise in sea level potentially over 230 feet (70 meters) over several thousand years.

In addition to the effects from temperature increases, Caldeira
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Contact: Dr. Ken Caldeira
kcaldeira@globalecology.stanford.edu
650-704-7212
Carnegie Institution
21-Sep-2005

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