| July 16, 2009 |  |
Study Says Climate Models May Underestimate Warming
Factcheck: Opposition Web Sites Misrepresent Findings
Several climate science contrarian Web sites are misrepresenting the findings of a peer-reviewed study published in the July 13 issue of the journal Nature Geoscience. The study—by scientists from Rice University, the University of Hawaii and the University of California at Santa Cruz—provides evidence that current climate models are underestimating the amount of warming that an increase in atmospheric carbon dioxide can cause. In other words, the potential consequences of global warming are likely worse than what scientists are predicting.
The study examined the extent to which increased carbon dioxide levels could explain a 5 to 9 degree Celsius increase the Earth experienced 55.5 million years ago. The authors concluded that current estimates of how much carbon dioxide increases the average Earth temperature only explains 3.5 degrees of warming.
In a commentary published with the study, David Beerling, a paleobiologist at the University of Sheffield in England, writes: "The upshot of the study…is that forecasts of future warming could be severely underestimating the extent of the problem that lies in store for humanity as greenhouse gases accumulate in the atmosphere."
According to Melanie Fitzpatrick, a climate scientist at the Union of Concerned Scientists (UCS), carbon dioxide-induced warming can lead to changes that exacerbate the problem. For example, increasing CO2 concentrations:
- melt tundra, which then releases methane and other heat-trapping gases into the atmosphere;
- warm the air, which then can hold more water vapor, another heat-trapping gas; and
- melt white ice, which exposes the ocean and land, which, because they are darker in color, absorb more heat from the sun and reflect less of it back into space.
Scientists are still trying to precisely quantify the effect of such "positive feedback cycles" that took place millions of years ago as well as the ones that are happening today, Fitzpatrick said. The scientific literature, including the new Nature Geoscience study, indicates that positive feedbacks greatly outweigh negative ones and that current climate models are likely underestimating potential temperature increases from overloading the atmosphere with carbon dioxide and other heat-trapping gases.
The Union of Concerned Scientists puts rigorous, independent science to work to solve our planet's most pressing problems. Joining with citizens across the country, we combine technical analysis and effective advocacy to create innovative, practical solutions for a healthy, safe, and sustainable future.
