No way back from climate change - January 27, 2009
Much like the sins in Pandora’s Box, once carbon dioxide is out, it’s not going away anytime soon. And it has real and quantifiable impacts.
In this week’s PNAS, Susan Solomon, of the US National Oceanic and Atmospheric Administration, and her colleagues report that “the climate change that is taking place because of increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop”. [Link should go live soon – ed.]
Using two different climate models the team show that peak carbon levels that could be hit this century will lead to “to substantial and irreversible” decreases in rainfall in some areas and “unavoidable inundation of many small islands and low-lying coastal areas”.
Solomon looked at carbon dioxide levels peaking at 450 to 600 parts per million by volume. As the NY Times notes many think 450 is “virtually inevitable” and 600 “difficult to avoid”.
“It has long been known that some of the carbon dioxide emitted by human activities stays in the atmosphere for thousands of years,” says Solomon (press release). “But the new study advances the understanding of how this affects the climate system.”
The Washington Post says:
Most previous scientific analyses, including the U.N. panel's summary report for policymakers, have assessed climate change impacts on a 100-year time scale. A few researchers, such as Ken Caldeira of the Carnegie Institution's Department of Global Ecology, have argued that it makes more sense to look at a time scale of at least 500 years.In an e-mail yesterday, Caldeira wrote that he had debated this point with other contributors to the U.N. reports in 2001, adding, "If you took our long term climate commitment seriously, you would not use 100-year [global warming projections] to compare effects of different gases."
Jonathan Overpeck, a researcher at the University of Arizona, told the LA Times, “As a climate scientist, this was my intuition, but they have done a really good job of working through the details and . . . make a case that the situation is more dire than we thought if we don't act quickly and aggressively to curb carbon dioxide emissions.”
As the researchers note in their paper:
It is sometimes imagined that slow processes such as climate changes pose small risks, on the basis of the assumption that a choice can always be made to quickly reduce emissions and thereby reverse any harm within a few years or decades. We have shown that this assumption is incorrect for carbon dioxide emissions, because of the longevity of the atmospheric CO2 perturbation and ocean warming.
Image: NASA
