Scientists puzzle over latest weird weather
US rides out La Nia. But is all the recent wackiness likely to persist in the long term?
Beach weather in New England before Mother's Day. Forest fires in northern Minnesota when residents are still scraping morning frost off their windshields. Golf in the high Rockies in February. Drought that leaves corn fields bare in the heartland.
What's going on?
Travel to virtually any corner of the United States, and it's easy to find local folks jawboning about the wacky weather. While some of the talk can be dismissed as overactive imaginations, weather experts say there's substance to what many people are feeling: The weather is changing.
How much is hard to tell, as meteorologists say they don't know where the trends are leading. During the past week, though, several announcements indicate that more extreme weather may be ahead.
*Forecasters with the National Weather Service say they expect the drought conditions now affecting the southern half of the nation - from Arizona through the Midwest down to Florida - will continue for three more months. Currently, 21 states are feeling the dry conditions, with 13 of them locked in severe drought at the start of the growing season.
*Along the Atlantic seaboard and Gulf of Mexico, coastal residents were told to expect a strong hurricane season in the wake of abating La Nia conditions. At least 11 tropical storms are predicted, with three or more forecast to turn into big hurricanes.
*As an indication of warming temperatures globally, the National Oceanic and Atmospheric Administration (NOAA) said three massive icebergs broke off from the Ronne Ice Shelf in Antarctica, showing that ancient ice caps are receding and oceans are rising.
"There is always something unusual with the weather going on," says Ed O'Lenic of the National Weather Service's climate operations branch. "There will always be anomalies, but the question is: Are these just typical anomalies or are they part of a pattern of events that is beyond normal explanation?"
The moderating of La Nia may ease the regional droughts of the past two years. But the change hasn't come in time to reduce sweltering temperatures.
Making educated guesses
Mr. O'Lenic says the current warming trend is leaving scientists somewhat at a loss, since weather data give few clues as to where the climate is headed.
"If you compare what has been going on recently to the last 400 years, this is unprecedented in terms of heat," O'Lenic says.
According to NOAA figures, 1999 was the second warmest year in the last century. In first place is 1998, and scientists believe it may have been the warmest in the past 1,000 years. Given the mild winter and the outlook for coming months, it is possible that this summer could surpass the last two, officials say.
"We have cause for concern because scientists are convinced that a significant part of this warming is caused by human-induced greenhouse gases from energy consumption," said NOAA administrator James Baker during a speech titled "The Future of Planet Earth," delivered at the Smithsonian Institution.
Experts say the continental US is already known as the stormiest nation on earth. When temperatures rise in all four seasons, there are likely to be larger tornadoes, bigger floods, and harsher droughts.
For the average citizen, that could mean more weather delays at the airport, more restrictions on watering the lawn, and higher prices at the grocery store, given impacts to crops and livestock.
Already, US agriculture officials estimate that the current drought has cost US farmers between $6 billion and $8 billion in lost production.
O'Lenic adds that different kinds of severe weather events can be interrelated.
Consider, for example, the phenomenon of "positive feed-back drought." Less moisture in the soil increases the radiation of sunlight which, in turn, results in rising ground temperatures. Drought begets heat, which exacerbates drought. Along with drought and heat comes a higher probability for wildfire.
New Mexico has seen as many acres of forest and grassland blackened as it normally experiences in an entire year, and summer hasn't even arrived.
Fires, in turn, can affect air quality for people living hundreds of miles downwind. This spring, the journal Science published a study showing that, in 1995, forest fires in northwestern Canada sent plumes of carbon monoxide into the air, reaching the eastern US 2,000 miles away. There, carbon-monoxide levels doubled in places and resulted in increased ozone.
In the case of fires, hurricanes, and floods, the events don't necessarily have to be more severe to cause more damage than they did in the past, says O'Lenic. The reason: With human population growing and spreading out, it's more likely that severe weather will affect some inhabited area.
(c) Copyright 2000. The Christian Science Publishing Society