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Why Leading Scientists Underestimated How Quickly We're Scorching the Atmosphere

The predictions about what climate change may bring are pretty dire, but now it seems, they were actually underestimated.

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There is a political and diplomatic incentive to low-ball emissions predictions becaue lower numbers make the task ahead appear less onerous.

"Overtly or covertly, if you have an optimistic baseline of what happens in the absence of policy, it makes what you need to do appear relatively modest," Caldeira says. "People who want to make the problem look more tractable have an incentive to make the baseline ore optimistic. If you have a more depressing picture, it's more difficult to make the transition."

For example, Caldeira says that if we're to stabilize atmospheric carbon at what's now considered tenable levels for the climate -- about 350 parts per million (we're now at about 385 ppm) -- the world's energy systems must be carbon neutral by mid-century. That's a daunting task that many governments appear hesitant to grapple with.

Not only has atmospheric carbon increased beyond the range of possibilities, but so too has effects of that increase on Earth's ecosystems. The retreat of Arctic Sea ice, the collapse of permafrost, ice sheet melt and that melting's contribution to sea level rise are occurring faster and with more intensity than expected. Atmospheric carbon dioxide, Field said, rose 3.5 percent annually between 2000 and 2007, compared with annual increases of 0.9 percent in the 1990s. Between 1993 and 2003, melting ice sheets accounted for 40 percent of sea level rise. That contribution is now estimated at 80 percent.

"The more we learn about the process [of climate change], the more severe the risk becomes," says Michael Oppenheimer, professor of geosciences and international affairs at Princeton University. Oppenheimer and Schneider are among the co-authors of a paper just published in the Proceedings of the National Academy of Sciences showing that the impacts of a 1-2° C rise in global mean temperature are much greater and pose greater environmental risks than previously anticipated.

Whether or not the Asian carbon surge continues, its impacts will be with us for decades -- even centuries -- because of the length of time carbon lingers in the atmosphere. "Nothing we could do now to stabilize carbon could be too fast or fast enough," says Tom Athanasiou, director of the organization Eco-Equity, an Earth Island Insitute-sponsored project. "The storyline was wrong."

The underestimation of recent greenhouse emissions threatens to complicate the work of government officials who will meet in Copenhagen in December to hammer out an international climate agreement to replace the Kyoto Protocol, which expires in 2012. With climate change occurring faster than scientists have the ability to predict -- and the impacts greater than anticipated -- an international deadlock is unacceptable, Anthanasiou says.

"Maybe the most important thing is to communicate the severity of the situation in a way that gets through people's defenses," he says.

Elizabeth Grossman, the author of High Tech Trash, is a frequent contributor to Earth Island Journal.

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