In his enviro-propaganda flick, An Inconvenient Truth, Al Gore claims nine of the 10 hottest years on record have occurred in the last decade. That's been a common refrain for environmentalists, too, and one of the centrepieces of global warming hysteria: It's been really hot lately -- abnormally hot -- so we all need to be afraid, very afraid. The trouble is, it's no longer true.

Last week, NASA's Goddard Institute for Space Studies -- whose temperature records are a key component of the global-warming claim (and whose director, James Hansen, is a sort of godfather of global-warming alarmism) -- quietly corrected an error in its data set that had made recent temperatures seem warmer than they really were.

A little less than a decade ago, the U.S. government changed the way it recorded temperatures. No one thought to correlate the new temperatures with the old ones, though -- no one until Canadian researcher Steve McIntyre, that is.

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In many cases, the changes are statistically minor, but their potential impact on the rhetoric surrounding global warming is huge.

The hottest year since 1880 becomes 1934 instead of 1998, which is now just second; 1921 is third.

Four of the 10 hottest years were in the 1930s, only three in the past decade. Claiming that man-made carbon dioxide has caused the natural disasters of recent years makes as much sense as claiming fossil-fuel burning caused the Great Depression.

The 15 hottest years since 1880 are spread over seven decades. Eight occurred before atmospheric carbon dioxide began its recent rise; seven occurred afterwards.

In other words, there is no discernible trend, no obvious warming of late.