You've probably heard about global warming—the heating up of Earth's atmosphere due to the buildup of carbon dioxide and other greenhouse gases. New analyses show just how warm the world is getting.

The year 2005 was the hottest ever recorded since scientists began keeping track of the numbers in the late 1800s. The average temperature around the globe last year was 14.6°C (58.3°F), say scientists from NASA's Goddard Institute for Space Studies (GISS) in New York.

This represents a 0.6°C rise in the last 30 years and a 0.8°C rise in the last 100 years. The warming trend doesn't prove that global warming is happening, or that pollution and the burning of oil and coal are to blame, but it matches predictions from computer climate models that support both theories.

Remarkably, five of the last eight years make up the list of the five warmest years of the past century, says James Hansen, GISS director. The second warmest year on record was in 1998, but there was also an El Niño event that year. The higher-than-average temperatures in parts of the Pacific Ocean during an El Niño usually boost the global average temperature. There was no El Niño to blame for the heat wave of 2005.

The most extreme temperature changes in the last 50 years have happened in places that have the coldest weather, including Alaska, Siberia, Scandinavia, Antarctica, and Canada. Last year, many places in Russia were at least 1.5°C warmer than they were between 1951 and 1980.—E. Sohn