Kevin Sweeney

Climate change was an ascendant news topic in 2006. There were a number of reasons — the film “An Inconvenient Truth” among them — but the primary one is clear: The science of predicting the climate is getting better, and the predicted effects of climate change are getting worse.

Many of the models used in the last decade to predict climate change effects appear to have been accurate, though with one key flaw: The onset of these effects may be faster than previously expected. Justin Mundy, a British Foreign Office official, put it succinctly at a recent meeting in Washington: “We assumed we had the luxury of time. Sadly, that is no longer the case.”

It was barely five years ago that the consensus among climate scientists was that, without significant changes in global carbon emissions, the Arctic Ocean would be icefree by the end of this century. By the end of 2006, many of those scientists said we were more likely to see open seas in the Arctic by 2040. (Arctic ice reflects heat away from the earth’s surface; its loss would cause more heat to be retained in our atmosphere. An effect of climate change could become a cause — one of the ironic “positive” feedbacks.)

James Hansen, NASA’s chief climate scientist, first warned Congress about climate change in 1988. In 2006, he began saying we have 10 years in which to begin taking serious action if we’re to avoid serious calamities. One example of what he considers a likely effect under a business-as-usual scenario: By the end of this century, 50 percent of the species that currently reside on earth will be extinct. If we take bold and quick action, Hansen says that number can be reduced to 10 percent, but there is that catch. We must make significant progress in the next 10 years — at least beginning the process of leveling off our carbon emissions — or the alternative scenario he offers is no longer viable. Without significant changes, we will create, in Hansen’s words, “a different planet.” We have 10 years to begin responding in earnest. 120 months.

The issue will remain in the news throughout 2007 and beyond. The International Panel on Climate Change (IPCC) will release various drafts of its fourth quadrennial report throughout the year, with new projections of climate impacts due out late in February.