BROWNE: Well, amidst all this talk of global warming, a winter weather warning in none other than Texas. Houston expected to break a record today with the earliest snowfall -- yes, snowfall -- ever recorded in that city's history. What's happening right now? Let's take a look. We're looking at these pictures right now courtesy of our affiliate KRIV. It is sort of hard to tell from this picture, but we have been watching this live shot for a while. And it does look like something is coming down, and we are hearing that snow is coming down. Snow is very rare in Houston. On average, it snows here once every four years, but according to the National Weather Service, Bill, Houston could get up to an inch today.
Many scientists also say that the cool spell in no way undermines the enormous body of evidence pointing to a warming world with disrupted weather patterns, less ice and rising seas should heat-trapping greenhouse gases from burning fossil fuels and forests continue to accumulate in the air.
“The current downturn is not very unusual,'' said Carl Mears, a scientist at Remote Sensing Systems, a private research group in Santa Rosa, Calif., that has been using satellite data to track global temperature and whose findings have been held out as reliable by a variety of climate experts. He pointed to similar drops in 1988, 1991-92, and 1998, but with a long-term warming trend clear nonetheless.
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Michael E. Schlesinger, an atmospheric scientist at the University of Illinois, Urbana-Champaign, said that any focus on the last few months or years as evidence undermining the established theory that accumulating greenhouse gases are making the world warmer was, at best, a waste of time and, at worst, a harmful distraction.
Discerning a human influence on climate, he said, ''involves finding a signal in a noisy background.'' He added, ''The only way to do this within our noisy climate system is to average over a sufficient number of years that the noise is greatly diminished, thereby revealing the signal. This means that one cannot look at any single year and know whether what one is seeing is the signal or the noise or both the signal and the noise.''
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Some scientists who strongly disagree with each other on the extent of warming coming in this century, and on what to do about it, agreed that it was important not to be tempted to overinterpret short-term swings in climate, either hot or cold.
Patrick J. Michaels, a climatologist and commentator with the libertarian Cato Institute in Washington, has long chided environmentalists and the media for overstating connections between extreme weather and human-caused warming. (He is on the program at the skeptics' conference.)
But Dr. Michaels said that those now trumpeting global cooling should beware of doing the same thing, saying that the ''predictable distortion'' of extreme weather ''goes in both directions.''
Gavin A. Schmidt, a climatologist at NASA's Goddard Institute for Space Studies in Manhattan who has spoken out about the need to reduce greenhouse gases, disagrees with Dr. Michaels on many issues, but concurred on this point.
''When I get called by CNN to comment on a big summer storm or a drought or something, I give the same answer I give a guy who asks about a blizzard,'' Dr. Schmidt said. ''It's all in the long-term trends. Weather isn't going to go away because of climate change. There is this desire to explain everything that we see in terms of something you think you understand, whether that's the next ice age coming or global warming.''