Periscope.

Byline: Fred Guterl (John Sparks Owen Matthews and Anna Nemtsova Jonathan Adams)

Climate: The Big Meltdown

Al gore is getting good reviews for "An Inconvenient Truth," a book and documentary film in which the former vice president warns us of impending catastrophe unless we curb carbon emissions. Gore raises the specter of eight-meter sea-level rises that would lay waste to London, New York, Shanghai and other coastal cities and redraw the world's maps. This water would come from the arctic regions, where glaciers are melting at an alarming rate.

The British journal Nature chose last week to publish a trio of scientific papers that, in a less politicized age, might have interested a few dozen scientists. They focus on what the climate was like at the North Pole 55 million years ago. Scientists have known that Earth was warmer then than it is now, but they didn't have any direct data from the North Pole, largely because getting it required drilling through 400 meters of seabed for core samples. The Nature authors did just that: two ships held the sea ice at bay while a third did the drilling. That's an expensive proposition to satisfy academic curiosity, but not to get important missing data in the global climate puzzle.

The conclusion that made the front pages of newspapers and Web sites last week was this: the waters of the North Pole seem to have been about 10 degrees Celsius warmer than scientists previously thought. How does this relate to the question we'd all like to know--how warm will the world get? That temperatures spiked sharply 55 million years ago suggests there may be a mechanism--high, heat-trapping clouds?--that kicks in to amplify warming beyond what you would expect merely from carbon. That's just what climate scientists fear. The Nature scientists did not find any clues as to what this mechanism might be, or if it even exists. The warming effect may have something to do with the continents, ocean currents and storm patterns, which were vastly different 55 million years ago. If so, it wouldn't have much bearing on our future.

The prospect of a balmy 23-degree ocean at the North Pole conjures just the kind of world Gore is warning us about. One of the Nature papers describes evidence that the Arctic was once dominated by lush ferns--a graphic scene that might have fit neatly into Gore's documentary. While we wait for answers, it might help to remember that it would likely take millions of years--not tens or even thousands--for the North Pole to sprout ferns again.

Fred Guterl