Wild, wet and warm: '05 a year of extremes

It's hard to say how much global warming or mere chance played a part.
Knight Ridder Newspapers
WASHINGTON -- It's not just your imagination. America's weather went wild this year.
It began with a record downpour in the Nevada desert and record warmth in Alaska, and it's ending with floods in California and wildfires in Texas and Oklahoma that have killed four people and consumed 37,795 acres.
Along the way, at least 214 climate records were smashed or tied, thanks to a slew of hurricanes, 21 straight days of 100-degree-plus temperatures in Fresno, Calif., and wildfires that have burned 8.64 million acres -- nearly a quarter-million more than the previous record, set in 2000.
Extremes were everywhere. Above-normal heat covered twice as much land as usual. Excessive rain and/or snow blanketed three times as much land as normal. Average daily low temperatures were warmer than normal across four times as much U.S. territory as in average years.
It was the third-worst year for U.S. extreme-weather events in history, according to the National Climatic Data Center. For 2005's first 11 months, the nation had an extreme-climate index figure of 35, behind only 1998's 42 and 1934's 37. The average annual score is 20.
One form of extreme weather fell short, however: tornadoes. In 2005, there were half as many killer U.S. tornadoes as recent norms.
The relentless Atlantic hurricane season especially marked 2005 as wild -- and tragic. Hurricanes set or tied 19 records, according to the National Oceanic and Atmospheric Administration, including:
U Hurricane Katrina caused $50 billion in insured damages.
U Hurricane Wilma set a hemispheric record for low barometric pressure.
U Three Category 5 hurricanes formed: Katrina, Rita and Wilma.
U A record seven major storms packed winds above 110 mph; the old record was five.
U Fourteen hurricanes in the season beat the old record of 12.
U The 26 named storms shattered the old mark of 21, set in 1933, causing meteorologists to run out of conventional names for hurricanes and tropical storms. They had to go five deep into the Greek alphabet for new names.
Many of the remaining extremes came from Alaska, which had 53 percent of the wildfire acreage burned and set temperature, rain and snow records almost weekly. That's because Alaska is getting hotter from global warming and its permafrost is melting, said Jay Lawrimore, the chief of the National Climatic Data Center's climate-monitoring branch.
It's less clear whether what's happening nationally can be attributed to global warming or results from mere chance. Scientists are researching the question on supercomputers. One theory is that warmer air holds more moisture, creating bigger downpours, snowfalls and stronger hurricanes, and that warmer air also worsens droughts.
Lawrimore said that one year's extremes couldn't necessarily be attributed to climate change and were more likely to reflect random weather shifts. But Kevin Trenberth, the climate-analysis chief at the National Center for Atmospheric Research, said initial studies showed that global warming might be a factor.