Don't stop worrying about global warming just because the wicked cold is breaking records in the Midwest and the East, climate experts say.
It would take more than a single deep freeze, they say, to discredit the widely accepted theory, which holds that gases produced by industry and agriculture are gradually warming the planet.
No one disputes that the cold is unusual. Low temperatures filled homeless shelters and closed schools throughout the Deep South yesterday -- breaking records in about 70 cities. Snow and ice over the past week have been blamed for 13 deaths in Minnesota, six in Illinois and four in Nebraska.
At the Baltimore-Washington International Airport, yesterday morning's low of 26 degrees shaved a degree off the record, set in 1952. The mercury plunged to 27 in Annapolis, 29 in Salisbury, 16 in Cumberland and 23 in Westminster.
But James Belville, a National Weather Service meteorologist, said that when it comes to local and regional weather patterns, the unusual is usual -- normal is just not normal. "Average temperatures are the mean between extremes," he said. And this week's chill is simply one extreme.
"You just can't take one event, one season or even one year of weather and say very much of anything about global warming," agreed Patrick Michaels, a University of Virginia meteorologist who has questioned how much and how fast the world's climate is changing.
Dr. Alan Robock, an associate professor of meteorology at the University of Maryland and the state's climatologist, said he hasn't seen anything in the past week to shake his belief that the global warming theory is valid.
"The observations are certainly good enough to show that it has warmed by about 1 degree Fahrenheit around the globe in the past 100 years," he said. Scientists link warming with gases, mainly carbon dioxide, released by the burning of fossil fuels and other human activities.
Dr. Robock pointed out that the lower 48 states make up just 1.5 percent of the Earth's surface. So even when record cold blankets two-thirds of the country, it chills only one small pocket of the globe.
Elsewhere, high temperatures may be setting records, meteorologists said, offsetting the cold weather recorded here. And this unusually cold late fall, they pointed out, follows several years of warmer-than-average weather.
"You have to look at the fact that 11 of the past 12 months in the Washington and Baltimore area have seen above-normal temperatures," Mr. Belville said.
So why the sudden chill?
"All this cold weather stems back to this wicked weather system that we had last week, where we had a very, very strong trough of low pressure develop over the central United States," Mr. Belville said.
That system caused polar air to seep down the Mississippi Valley like molasses, finally oozing into Maryland and the East on Monday.
Mount Pinatubo, a Philippine volcano that erupted in June, is expected to cool global temperatures by as much as 1 degree over the next couple of years. That's because the millions of tons of gas and dust it shot into the upper atmosphere will reflect sunlight. But Dr. Robock and other scientists said Pinatubo probably can't be blamed for this week's cold weather. That's because El Nino, a periodic warming of the equatorial Pacific's surface waters, is occurring now and probably canceling out the volcano's cooling.
Meanwhile, back in Baltimore, meteorologists predicted that the temperature this morning would fall to the mid-20s but probably would not break the record of 23.