Mar. 28, 2003 CHAMPAIGN, Ill. -- Uncertainty in the climate sensitivity to growing levels of atmospheric carbon dioxide has been a stumbling block to policy makers addressing the climate change issue. A study published in the March 28 issue of the journal Science, however, concludes that huge reductions in fossil-fuel carbon emissions will be required by the middle of this century -- regardless of the likely climate sensitivity.
"To reduce carbon dioxide emissions and avoid dangerous interference with the climate system, we must switch to alternative, carbon-free energy sources," said Atul Jain, a professor of atmospheric sciences at the University of Illinois at Urbana-Champaign and a co-author of the study.
Jain and his colleagues -- lead author Ken Caldeira, a senior scientist at the Lawrence Livermore National Laboratory, and Martin Hoffert, a professor of physics at New York University -- found that even if climate sensitivity is in the low end of the accepted range, climate stabilization will require a massive transition to carbon-emission-free energy technologies during this century.
Climate sensitivity is the global mean temperature change that would result from doubling the amount of carbon dioxide in the atmosphere. Based on current models, climate sensitivity is thought to lie between 1.5 degrees Celsius and 4.5 degrees Celsius.
In their study, which was funded by the U.S. Department of Energy, the researchers constructed stabilization pathways that led to a 2 degree Celsius warming after the year 2150. For each of the pathways, they calculated the allowable carbon dioxide levels using a globally aggregated Earth system model called the Integrated Science Assessment Model.
If climate sensitivity is at the high end of the range, then by the end of this century nearly all of our power will have to come from non-carbon-dioxide-emitting sources, the researchers found. "We must begin replacing fossil fuels with alternative energy technologies that support economic growth and equity," Jain said. "To achieve stabilization at a 2 degree Celsius warming, we would need to bring the equivalent of a large carbon-emission-free power plant into production somewhere in the world every day for the next 50 years."
The study concludes: "We do not now have non-carbon-dioxide-emitting energy technologies that can be applied today at the required scale. Given the long lead times needed for market penetration of new energy technologies, we need to develop appropriate energy technologies now."
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