Carbon emissions will last for millennia, expert says

02/24/2009 1:07 PM

03/12/2009 3:09 PM

WASHINGTON — Until now, most discussion of climate change has been about what scientific evidence shows is likely to happen between now and 2100. However, scientific research shows that the carbon dioxide gas released from burning fossil fuels lasts in the atmosphere much longer than mere decades.

David Archer, a leading climate researcher who teaches at the University of Chicago, has written a new book that looks at carbon dioxide's "long tail" and what it means for changes on Earth in the future.

If the world continues its heavy use of coal over the next couple of hundred years until it's essentially used up, it would take several centuries more for the oceans to absorb about three-quarters of the carbon dioxide emitted into the atmosphere. In those centuries, there would be a "climate storm" that Archer says would be significantly worse than the forecast from now to 2100.

The remaining carbon dioxide — the long tail — would stay in the atmosphere for thousands of years, leaving a warmer climate. About 10 percent of it would still be in the atmosphere in 100,000 years, Archer wrote in "The Long Thaw: How Humans Are Changing the Next 100,000 Years of Earth's Climate."

"Ultimately, the amount of fossil fuel available could be enough to raise the atmospheric CO2 concentration higher than it has been in millions of years," Archer wrote.

Because of the long life of CO2 from fossil fuels, the climate impacts would last for many thousands of years. Ice sheets would melt, raising seas high enough to swamp 10 percent or more of the world's agricultural land. Other climate impacts could include uncomfortable heat and drier continental interiors, Archer tells his readers. "In the long run, it could be a steep price to pay for a century or so of fossil fuel energy."

Archer studies the carbon cycle of Earth as it interacts with global climate. His slim book is a clear explanation of carbon dioxide and climate change for nonscientists. It also explains how the climate has changed in the distant past and looks ahead to the deep future.

His work has been a part of what John Holdren, whom President Obama named as his science adviser, has called the "tremendous effort" among scientists to reach a "center of gravity" in the understanding of climate change. The results of that work are available in the reports of the National Academy of Sciences and the Intergovernmental Panel on Climate Change. The conclusion, as Holdren summed it up at his confirmation hearing recently: "Climate change is real, it's accelerating, it is caused in substantial part by human activity, it is dangerous and it is getting more so."

Like Holdren and other climate experts, Archer concludes that there's still time to cut fossil fuel emissions enough to avoid disaster.

"The question may come down to ethics, rather than economics," Archer wrote, much as the issue of slavery did more than a century ago. "Ultimately it didn't matter whether it was economically beneficial or costly to give up. It was simply wrong."

Some questions and answers with David Archer:

Q: You write that the climate effects of fossil fuel burning will last longer than nuclear waste. Most discussions of climate change focus on this century. Why did you look farther out?

A: Everyone knows that nuclear waste lasts a long time, and it seems to make a difference to them. It makes a difference to me the longevity of global warming, too.

Q: Some people, though, don't believe it's a problem.

A: There are people who will "believe" anything they want to; the question is whether anyone has a scientifically credible justification for that belief. It was predicted over a century ago that rising CO2 concentrations in the air would warm the planet. Now it seems to be doing just that, just as predicted. If anyone can explain why things should not work in this way, then I'd be interested to hear, but so far there are just no completing ideas, just beliefs stemming from whatever source, and an active campaign at disinformation sponsored by the fossil fuel industry.

Q: What difference does the long view make?

A: The book makes the point that global warming from CO2 emissions will last for thousands of years into the future. To me that changes the picture, especially when thinking about the economics of climate change or the possibility of "engineering" the planet cooler by putting haze in the stratosphere or something like that. It also means that the eventual sea level rise from releasing CO2 could be a hundred times greater than the forecast for the year 2100.

Q: Is Earth doomed to an ice-free state, mass extinctions and rising seas?

A: No, the damage has not yet been done. We could stop releasing CO2. Technologically that is not so hard.


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