SAN FRANCISCO--A trend toward a warmer Earth shows no sign of abating, the latest climate statistics reveal. As of 30 November, worldwide surface temperatures mark 2000 as the fifth-warmest year since 1880, while the United States was headed for an all-time record until a frigid November set in. Officials from the National Oceanic and Atmospheric Administration (NOAA) released the figures here on 19 December at a meeting of the American Geophysical Union and at NOAA headquarters in Washington, D.C.
Average global land and ocean temperatures have climbed at a rate of 0.2°C per decade since 1976, according to data compiled by the National Climatic Data Center (NCDC) in Asheville, North Carolina, and the World Meteorological Organization (WMO) in Geneva, Switzerland. Despite annual fluctuations, the trend is clear: The 10 warmest years on record have occurred since 1982.
This year, it appears that a waning La Niña--which cools the tropical latitudes--kept the worldwide average land and ocean temperature from exceeding its peak value of 14.6°C (58.1°F), set in 1998. Excluding temperatures from December, which are still being gathered, 2000 is tied with 1999 as the fifth-warmest year at 14.3°C (57.6°F), says NCDC director Thomas Karl. However, Karl observes that temperatures in 2000 were the second-warmest on record for the region north of 20° latitude, beyond La Niña's direct influence. "Global warming continues, although not at the record levels of 1998," Karl states.
The current heating trend is not unprecedented in the last century, Karl observes. From 1910 to 1945, the mercury rose at a rate of 0.16°C per decade, driven by vigorous solar activity, the initial rise in industrial greenhouse gases, and fewer big eruptions. Indeed, several of the hottest U.S. years on record occurred during the 1920s and 1930s (see chart below). In 2000, average temperatures in the U.S. soared beyond those Dust Bowl heights until last month, which was the second-coldest November on record in the 48 contiguous states. Extremely cold months still occur, Karl notes, although statistics suggest that they have become less frequent since 1976.
Y2K summary statements from the NCDC and the WMO brim with other climatological oddities and arcana. For instance, England and Wales experienced their wettest autumn in 235 years of records, while summer in the south-central U.S. was the driest since 1880. Nearly 70 centimeters of rain in 24 hours drenched Hilo, Hawaii, in early November, obliterating the previous one-day record by 13 centimeters. Further north, residents of Barrow, Alaska, witnessed their first thunderstorm in modern history on 20 June.
Statistical variability accounts for some of these bizarre incidents, Karl notes. Still, he says, "One of the clearest signals we see is that an increase in global temperatures leads to an increase in extreme or heavy precipitation events."
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