Firestorms and Deep Freeze: Climate Change May Bring Both

By Scott Thill, AlterNet. Posted February 16, 2009.

"The potentially severe consequences of such an event, even if very unlikely, argues for a strong research effort to develop the observations, understanding and models required to predict more confidently the future evolution of the Atlantic Meridional Overturning Circulation (AMOC), or thermohaline circulation (THC)," warns Thomas Delworth, a scientist at the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory in Princeton, N.J., as well as the convening lead author of a chapter on THC recently released in a voluminous report on global warming from the U.S. Climate Change Science Program.

"Based on our synthesis of the research to date, it is very likely that the strength of the THC will decrease over the course of the 21st century in response to increasing greenhouse gases, with a best estimate decrease of 25-30 percent.

"However, our assessment was that a collapse of the THC in the 21st century has less than a 10 percent chance, based on the fact that none of the state-of-the-art climate models project such a collapse when subjected to our best estimates of future changes in greenhouse gases and other factors that influence climate. However, although our current understanding suggests that such an event is very unlikely, the potential consequences of such an event could be severe."

Of course, NOAA's best estimates are likely as solid as those of the Nobel Prize-winning Intergovernmental Panel on Climate Change, whose scary 2007 report is already, according to the World Wildlife Fund, woefully out of date. Everything is worsening beyond what Earth's greatest scientists have concluded in what Delworth might call their "state-of-the-art climate models," which is a nice way of saying that they missed the forest for the trees.

So if you think a collapse of the THC is out of bounds, you might want to think again, and perhaps consider moving to, ironically enough, warmer climes if you live in the U.K. or the U.S. East Coast.

"There are some important climate processes that have a significant effect on regional climate, but for which the climate change response is still poorly known," explains the U.N.'s Liu. "These include thermohaline circulation. The uncertainties surrounding this, however, are high. Some measurements have detected evidence of weakening, while others point to a warming North Atlantic, implying that circulation is not weakening, or if it is, it is not having a cooling effect, or other factors are overriding the cooling effect.

"The general view is that the shutdown of the thermohaline circulation is a low-probability event, but one that would have major consequences."

That general view is in stark contrast to that of Michael Schlesinger, a professor of atmospheric sciences at the University of Illinois, Urbana-Champaign, who in 2005 infamously declared that the "shutdown of the thermohaline circulation has been characterized as a high-consequence, low-probability event. Our analysis, including the uncertainties in the problem, indicates it is a high-consequence, high-probability event."

Whatever the scientific consensus, or disagreement, we can't wait hundreds of thousands of years to see if the U.K. and U.S.' bitter cold will turn into an ice age, even as the rest of the planet burns. We need to act now. Liu suggests we start with the obvious.

"There is substantial economic and technical potential for mitigating climate change by reducing greenhouse-gas emissions, as well as enhancing sinks," he says. "Quite a number of policies exist in countries, both developed and developing, which, if implemented, could lead to emission reductions and contribute to sustainable development. And there are various ways in which greenhouse-gas emissions can be reduced: Using and saving energy more efficiently, replacing nonrenewable with renewable sources of energy, capturing and sequestration of carbon-dioxide emissions, and enhancing the carbon-dioxide-sink function of forests."

But even that won't stop the pain. Liu adds:

"Even if the most stringent mitigation measures were put in place today, the impacts of climate change would still continue for centuries."

See more stories tagged with: global warming, climate change

Scott Thill runs the online mag Morphizm.com. His writing has appeared on Salon, XLR8R, All Music Guide, Wired and others.

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