2005 Vying With '98 as Record Hot Year

Four separate temperature analyses released Thursday varied by a few hundredths of a degree but agreed it was either the hottest or second-hottest year since the start of record-keeping in the late 1880s. Unlike 1998, however, 2005 had no El Nino -- a natural weather phenomenon -- to warm ocean waters, which affects temperatures worldwide.

The planet has been slowly warming for a century, and the 10 hottest years on record have all occurred since 1990, a trend that a majority of scientists say is in large part attributable to human production of greenhouse gases, which trap heat in the atmosphere.

"The last 10 years have been exceptionally warm," said Raymond Bradley, a climate scientist at the University of Massachusetts in Amherst. "2005 continues this extraordinary sequence of warm temperatures."

This year saw above-average temperatures across the majority of the planet, with extreme warmth in the high latitudes of the northern hemisphere, including Alaska, Russia and Scandinavia, said Jay Lawrimore, chief of the climate monitoring branch of the National Oceanic and Atmospheric Administration.

A minority of scientists dispute the findings and say the measurements used to take the planet's temperature are spotty, inaccurate and may exaggerate the amount of warming.

"We're asking too much of the data," said Roger A. Pielke Sr., Colorado's state climatologist.

According to scientists at NOAA, a preliminary ranking shows that 2005 was 1.06 degrees warmer than the long-term average of 57 degrees, and 1998 was 1.12 degrees warmer. When final numbers for 2005 and an improved analysis system are used early next year, 2005 is likely to end up being ranked as the hottest year, Lawrimore said.

A NASA analysis showed 2005 to be the hottest year, while analyses by the United Nations World Meteorological Organization and the U.K.'s climate authority, the Hadley Centre, showed 2005 to be a close second to 1998. The groups use the same temperature data but differ in how they analyze them, particularly in remote areas such as the Arctic, where there are few thermometers. The numbers also vary because the groups use different adjustments to remove the "urban heat island effect," which causes warmer temperatures in areas with large amounts of pavement, buildings, people and cars.