Weather changes are less than meet the eye

Extremes don't prove major trends at work, climate experts say

January 18, 1999|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

It was 77 degrees in Baltimore on two days last month. Two weeks later, it was snowing.

Buffalo got 50 inches of snow in the first two weeks of 1999. It was 70 degrees in Goldsboro, N.C., Thursday and a record 55 below zero Friday in Allagash, Maine. Those extremes came on the heels of a year with record-breaking tornado outbreaks, awful ice storms, floods, mudslides, droughts, wildfires and millions of dollars in crop losses.

Have the wheels come off the weather bus?

"People have been asking that question continuously for as long as I've been in the business," said Robert E. Livezey. A senior research meteorologist at the National Centers for Environmental Prediction in Camp Springs, he has been in "the business" for 25 years.

In one sense, it might be true.

"I don't think there is much question anymore that we have been living in an era of a warming Earth," Livezey said. "The evidence is getting to be very compelling." Meteorologists must now take that into account in their seasonal forecasts.

Although it amounts to just 1 degree globally since 1900, the temperature rise has been far larger, more than 8 degrees, in parts of the western United States. In those places, Livezey said, "if the public perception is that maybe they're not getting as many cold winters as grandpop said he experienced, there's probably some truth to that."

But most events perceived as unheard-of weather extremes or climate change, scientists say, are more likely a product of short memories or false perceptions, jazzed up with media overkill.

"A great deal of what goes on in the weather for the most part has a precedent somewhere," Livezey said. "It's either in the very carefully recorded past, or we can infer it from proxy information" such as ice and sediment cores, tree rings or coral reefs.

"A good example is the El Nino last year. There is lots of evidence there was an El Nino just as strong, and with the same dramatic impacts, back in the 1800s," he said.

Joseph Tribbia, a scientist at the National Center for Atmospheric Research in Boulder, Colo., said scientists in the mid-1980s noted extreme climate variability in the United States. In the journal Science, they wrote that the nation had experienced a number of extremely cold winters from 1977 to 1985, interspersed with extremely mild winters. They concluded that the climate was changing.

"It turned out that climate variability had undergone some changes," Tribbia said. "But if you looked at the historical record, it looked like the abnormal period was from the mid-'60s to the mid-'70s, when there wasn't much extreme behavior going on."

Our perceptions of the climate are pretty distorted, said Michael Glantz, senior scientist at the atmospheric research center. "Farmers in the Midwest don't remember the '50s. They definitely don't remember the '30s. Their experience is just two decades, generally. So they'll say, `It's the worst drought ever.' But really, maybe, it's the worst that they have seen, or experienced, or that they remember."

"It's the nature of climate to be variable, and people tend to confuse variability with change," said Dale Jamieson, a professor of philosophy at Carleton College in Northfield, Minn. He also serves as an adjunct scientist at the atmospheric research center, specializing in weather's societal and environmental effects.

In 1979, all five Great Lakes froze over for one of the few times in recorded history. Books and magazine articles fretted about "global cooling." Four years later, all of the lakes remained ice-free for the first winter in recorded history.

Jamieson also believes our perceptions of weather and climate are colored by "heuristics," psychological shorthand that helps us weigh probabilities and manage risk in our daily lives. We are able to drive to the store for milk, for example, because we have discounted the risk of being killed in a wreck en route.

Similarly, we discount events of the more distant past. Baltimoreans marveling at how mild the last two winters have been may already have forgotten the 22-inch "Blizzard of '96" or the repeated ice storms in early 1994.

On the flip side, "We tend to react very strongly to an experience that is vivid to us," Jamieson said. "If we had a warm winter last year, we tend to say, `The weather is really changing. It's never been that warm,' " Jamieson said.

News of broken weather records can give the impression that things are out of kilter. But there are records for every day in every city, and some go back less than a century. They're always being broken somewhere, Livezey said. That's weather. It's short-term and, by itself, doesn't translate into long-term trends or climate change.

"We think our memories are pretty robust, and that we have a good gauge of changing weather," Tribbia said. "But in fact, we're likely to be fooling ourselves quite a bit."

Glantz grew up in Rhode Island. "The snows were humongous," he said. "But I was 3 feet tall. Our perspective changes."

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