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Allan's TIME > News > Wild Weather

Why has our weather gone wild?

This story was received by e-mail.  The URL source cited was not accurate, but seems to be attributed to Discover magazine.  It is posted here temporarily until the source is identified.  The paragraph returns are missing in this version.

Why has our weather gone wild? The evidence increasingly points to global warming as the culprit. And if you think mother nature's shifts from one extreme to another are bad now, brace yourself for the future By Joseph D'Agnese As you read this,flip your eyes over to the window. The sky is clear, the wind light, and the sun brilliant. Or maybe not--Mother Nature is full of surprises these days. The calendar says it's spring, but there could just as easily be a winter blizzard, a summer swelter, or an autumn cold snap on the other side of that glass pane. Almost in an instant, it seems, the weather shifts from one season to another. And wherever it swings, it seems increasingly likely to be extreme. Consider what Mother Nature slung our way last year in May, typically the second worst month for tornadoes. In less than 24 hours, more than 70 hellholes of wind rampaged through Oklahoma and Kansas, killing 49 and causing more than $1 billion in damages. In June, it was heat, as the northeast began roasting through weeks of the worst drought since the 1960s; 256 people died. Last September, Hurricane Floyd forced the largest peacetime evacuation in U.S. history, as 2.6 million people scurried for safety, and huge sections of the East Coast went underwater, drowning hundreds of thousands of farm animals. This year in January, blizzards pounded the nation from Kansas to the Atlantic Ocean. In April, 25 inches of snow fell on parts of New England. In the midst of one of those January blizzards, two scientists who had traveled to Washington, D.C., found themselves canceled out of a seminar and out on the street trying to find a way home. As they began walking away from their hotel, they passed a local TV news crew asking passersby how much havoc the weather was wreaking in their lives. The two scientists, climatologists John Michael Wallace and Kevin E. Trenberth, briefly considered getting their mugs on TV, then thought better of it. The question they didn't want to answer: Why has our weather gone wild? It's the question everyone's asking, but a very tough one to answer. Although many scientists still aren't convinced that it has gone wild, some have begun saying--cautiously, hesitantly--that extreme weather events are occurring with more frequency than at any time in this century, events consistent with the profile of a warming world. "Global warming is real," says Trenberth, head of the Climate Analysis Section of the Center for Atmospheric Research in Boulder, Colorado. "The mean temperatures are going up. The key question is: What will it do locally? I think we're going to start feeling its effects in the changes on extremes." That doesn't mean you can indict weird weather in your neck of the woods as proof. Mother Nature knows how to hide her tracks. She hurls a torrential downpour today and a drought tomorrow followed by gentle rain the next week. To discern a pattern in natural variability, you can't look into the sky; you have got to study data. And for a host of reasons, that isn't easy. But tallying up the damage is. In the last 20 years, this country has been whacked by $170 billion worth of weather-related disasters--hurricanes, droughts, floods, and tornadoes. Thirty-eight severe weather events occurred in a single decade, between 1988 and 1999; seven severe events occurred in 1998 alone--the most for any year on record. Globally, insurance companies are calling it a "catastrophe trend." In a report issued last December, Munich Re, the world's largest reinsurer, or insurer of insurance companies, noted that the number of natural disasters has increased more than fourfold since the 1950s. Earthquakes, which are not weather-related, caused nearly half the deaths in those catastrophes; storms, floods, and other weather woes killed the other half. In 1999, the number of catastrophes > worldwide--including mud slides in Venezuela, a severe hailstorm in Sydney, avalanches in the Alps, Denmark's worst winter storm in a century, floods in Latin America and Southeast Asia, Cyclone Bart in Japan and Cyclone 05-B in India--hit 755, surpassing the record of 702 set only the year before. In its five-point list of causes for increased damage claims, Munich Re blamed population growth first, climate change fifth. Critics may well seize upon this to diminish claims that the weather is getting worse, but taken together, it's a scarier picture. Thanks to swelling populations in cities and along coastal areas, more of Earth's passengers are living in the wrong place at the wrong time. Still, the statistics meteorologists have collected on extreme weather events aren't enough to prove that the weather is getting worse. By their very definition, extreme events happen infrequently, and no one has been collecting scientifically sound data long enough to know how common they are. For example, a storm that happens once a century might require two millennia's worth of storm data to draw conclusions. To top it off, the computer models scientists use to study climate crunch numbers on a scale of centuries at a time. "Ideally, you'd like data sets that go back several hundred years," says Philip Arkin, deputy director of the International Research Institute for Climate Prediction at the Lamont-Doherty Earth Observatory in Palisades, New York. "But they just don't exist. The U.S. data go back 50 years. Before World War II, it's very difficult to come up with good numbers. We have some data on heavy rain events before 1900, but there's nothing useful." Even if scientists could find good numbers, computer resolution is still too coarse to be able to forecast how something as simple as warming might affect climate in specific spots on the globe. The smallest amount of space on land, sea, ice, and air that scientists can study is roughly the size of Virginia. If they crank up the resolution by 50 percent to focus on an area half that size, they pay for it in computing time--a calculation that took 10 days to perform might now need three months. Keith Dixon, a research meteorologist at the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey, recalls once being asked precisely what global warming would mean for state ski resorts. More snow? (Good.) Or more rain? (Bad.) "I can understand why businesspeople or politicians ask. If you want to cut fuel, spend money, and make decisions, you need to know why you should be doing this." Adds his colleague, Tom Knutson, another GFDL modeler: "I can certainly sympathize with them. But we can't answer it." Since 1995, the literature has suggested that there could be fewer frosts, more heat waves, more droughts, more intense rainfalls, tropical cyclones, and hurricanes in the 21st century when and if CO2 levels double. But these projections rank low on the confidence scale because scientists cannot say definitively if and how the events might occur. All of which doesn't do the average citizen much good. He doesn't worry much about 30-to-100-year shifts in the climate. What gets him is day-to-day weather: "This heat's killing me." "Crops have failed here five years in a row." "There have been three bad tornadoes in as many weeks." We live in a society uniquely privileged to learn about weather events--and to fear them. The Center for Media and Public Affairs, a watchdog group based in Washington, D.C., reports that media coverage of weather disasters more than doubled from 1997 to 1998 alone. Probably as a result, people are starting to blame harsh weather on global warming. Politicians are too. Jerry Mahlman, director of the GFDL, advises the White House on climate change. He remembers sitting in a conference with Vice President Gore, who asked: "Can we say that storms will be more extreme in the greenhouse-enhanced earth?" The scientist didn't flinch as he replied, "No." Gore's shoulders seemed to crumple. Globally, the 1990s stood out as the warmest decade for which we have records. Scientists already predict that by 2100, Earth could warm up another 1.8 to 6.3 degrees Fahrenheit. Most of us think heat when we think global warming. Scientists think ice. They're worried about what will happen when all that extra heat hits the ice at Earth's poles. A dominant hypothesis says that the water cycle will speed up: Heat will hasten ocean evaporation, and because hot air can hold more moisture, it could all be whisked away to rain more upon our heads. Five years ago, the Intergovernmental Panel on Climate Change, an international collaboration of 2,000 scientists, theorized as much in a well-publicized 56-page report. That same year, a team of scientists led by Tom Karl, now director of the National Climatic Data Center (NCDC), the nation's weather archives in Asheville, North Carolina, studied 80 years of U. S. data and confirmed an increase in extreme precipitation events, altered patterns of rain and drought, and rising temperatures since 1970. But the scientists cautioned that the study analyzed only 80 years of data, confined itself to the United States--which occupies a mere 2 percent of the globe--and found nothing out of the realm of pure chance. Within months came another, stronger piece of real-world data, nailed down by one of the men caught in that January snowstorm. Sifting through historical data, Trenberth had found that more, longer, and stronger El Ninos have occurred during the last 20 years than in the previous 120 years. That was unusual, a chance of 1 in 2,000. El Nino, the periodic warming of the equatorial Pacific that induces storms and other climatic events, historically occurs once every three to seven years and lasts for up to two years. But even as Trenberth presented his findings at a conference in Melbourne, Australia, the Pacific was experiencing an odd, double El Nino: The first had lasted from 1991 to 1993, a weaker one from 1994 to 1995. Trenberth floated an idea past the audience in his native New Zealand accent: Could this be due to global warming? The idea, Trenberth modestly recalls, caused something of a stir in the audience. Scientists found themselves wondering: What would happen if one of nature's storm machines--not completely understood but still adhering to rhythms as regular as the seasons--were pressed into service by global warming? Archaeological evidence suggests El Nino has been around for thousands, possibly millions of years. A known instigator of storms, floods, droughts, and secondary effects like fires, the El Nino-Southern Oscillation could go a long way toward explaining many weather extremes. Under normal circumstances, sea surface temperatures rise in the tropical Pacific, fueling strong thunderstorms. Like a vast climatic mailbag, El Nino-enhanced activity hand-delivers heat and moisture to parts of the globe where they would not normally go. Contrasting cool ocean currents in the Pacific can usher in the opposite phase, La Nina, which tends to dry out the southwestern and South Central states. La Nina also exacerbates weather conditions but rarely bullies as harshly as El Nino. "The Americas are greatly affected by El Nino," Trenberth says. "Europe is much less affected. If things do become more El Nino-like, then it does have implications for different parts of the country. It means we're more likely to have storms coming into southern California and going across the south, at least in the wintertime. If 1998 was any indication, you have to really watch out for the seasonal change, where it can go from wet conditions to quite dry conditions when the storm tracks move farther north." In the early 1990s, El Nino helped parch Indonesia and other tropical Pacific climes and blister southern Africa, but it drenched California. Together Nino and Nina did a number on the Americas. From 1992 to 1993: winter floods in California. In 1993: flooding in the Mississippi Basin, drought in the Carolinas. From 1994 to 1995: more floods in California. In 1996: drought in the South Central states, flooding in the Midwest. The strongest El Nino on record, from 1997 to 1998, registered water temperatures as high as nine degrees above normal. "A normal, run-of-the-mill El Nino is about two or three degrees Fahrenheit above normal," says Trenberth. "This one was nine, so it was a real granddaddy in that respect." That was the year Hurricane Mitch left at least 11,000 dead in Central America. The NCDC calls Mitch the deadliest Atlantic hurricane since 1780. Today Trenberth's hypothesis is high on the agenda in such climate labs as the Geophysical Fluid Dynamics Laboratory in Princeton, the Max Planck Institute in Hamburg, Germany, and others in England, Australia, Canada, and Japan. Says Lamont-Doherty's Arkin, "It would be hard to talk about extreme weather without considering his work." But Mahlman says: "It's a good hypothesis; there's a shred of truth to it. But it still seems like a coin flip." Reviewing results in his lab in the foothills of the Rockies, Trenberth is the first to poke holes in his own work. "Part of the problem is that all the models tend to give different answers to this question," he says. "But a lot of these models don't reproduce El Nino very well in the first place. So the confidence in what they're telling you is undermined." Still, Trenberth believes we are likely in the coming century to see ever longer El Ninos fluctuating with shorter La Ninas. Weather, including bad weather, might therefore appear to be more fixed. "That's the main thing El Nino or La Nina does for you," he says. "It locks the patterns in. So once you get into a dry regime, you stay in a dry regime. If you get into a wet regime, you stay in a wet regime. And so you tend to get these extremes--you get battered by one storm after another. Or else you get dry spells time after time." Baltimore residents may recall that they sweltered in last summer's heat wave and drought only to be soaked by Hurricane Floyd whisking through in September. Scientifically, one cannot directly blame that mess on El Nino or global warming. "It was very regional," Trenberth says. "There are a number of factors that go into that, part of which was La Nina, part of which was what was going on out over the Atlantic. It's not representative of what's going on in lots of other places around the world--except that if it happens more and more in different places around the world, the evidence mounts that something is pushing you in that direction. The global perspective is important with regard to the global warming issue. Just watching things go by locally can help to create the overall picture, but it doesn't confirm it at all." So: Is the weather getting worse and wilder? Maybe. Perhaps the best line on this topic was penned by the director of the Geophysical Fluid Dynamics Laboratory. In an article published last year, Mahlman wrote: "For me, the new data . . . indicate that we appear to be nudging noticeably closer to the Osmoking gun' demanded by people who require very high levels of proof." Trenberth regards extreme weather as an analogue, a dry run to the future. And it isn't pretty. Droughts rob us of sustenance and leave us vulnerable to fire. In wet, warm conditions, insects thrive. The United Nation's World Health Organization already reports that mosquitoes carrying malaria and dengue fever have hit new highs in Latin America, Africa, and Asia. In the United States, cycles of rain and drought seven years ago permitted a deadly form of pulmonary hantavirus, carried by mice, to flourish in the Southwest. And last summer, the first cases of West Nile virus reported in this hemisphere popped up in New York City. Officials say mosquitoes that survived last year's malathion spraying patiently waited out the winter of 1999 in the city's subways. Handed a dress rehearsal, perhaps we should use it. We can develop strategies to cope. We can cultivate an interest in the weather outside of our commutes. And we can shake the habit of sampling locally and extrapolating globally. Last winter, some weeks before he got stuck with Trenberth in that January snowstorm, Wallace, a professor of atmospheric sciences at the University of Washington and a specialist on El Nino and global climate, flicked on the TV to watch his first-ever appearance on CNN. His clip was followed by a short segment on New England's weather. "There was a guy about my age reminiscing about what fun kids used to have skating on a pond," recalls the 59-year-old Wallace. "That really resonated with me because I grew up in Massachusetts and had a lot of the same kinds of memories. He said the skating season had been very short and it looked as if it would be nonexistent this year. He added, OYou don't have to be a rocket scientist to know that the climate has warmed.' I might have taken offense at that, but actually my reaction was quite the opposite. That is how people assess weather if they've seen change in their lifetimes. They're going to do it whether we say they should or not. Whatever the scientific community says, the weather's going to be judged in light of those memories." Is the Weather Driving You Crazy? ohn S. Westefeld has seen lots of strange neuroses in his 22-year career as a counseling psychologist, but few strike him as odd as those exhibited by patients who become agitated and anxious as soon as they hear predictions of storms. As the bad weather gets closer, they get more and more upset, calling in sick to work, hunkering down indoors with their eyes glued to the Weather Channel, and even refusing to leave the house to pick up their kids at soccer practice. "They are immobilized by fear," he says. "Even if the danger is way down the line." Westefeld has a name for them: Severe-Weather Phobics. Maybe we should have seen it coming. After all, everyone knows rainy days make us blue and sunny days make glad our hearts. And an increasing number of scientists are saying peoples' reactions to weather are more than psychological. Researchers called biometeorologists and bioclimatologists believe shifts in temperature, humidity, cloud cover, wind speed, and barometric pressure have direct, precise effects on health and behavior, and they believe our bodies are hardwired to pick up cues from the weather. It's a concept that spans millennia. Even Hippocrates suggested that weather was responsible for patients' ills. "South winds induce dullness of hearing," he wrote, "but if the north winds prevail, coughs, infections. . . occur." In his folksy book Weathering, physicist Stephen Rosen rattles off a list of other famous believers in the mind-body-weather phenomenon, including Columbus, Darwin, Ben Franklin, Johannes Kepler, Blaise Pascal, and Leonardo da Vinci. All attributed their own behavior and mood shifts to what was happening in the sky. Writers and poets, too, have long limned a connection. Wrote Raymond Chandler in a moody Philip Marlowe short story: "There was a hot desert wind blowing that night. It was one of those hot dry Santa Anas that come down through the mountain passes and curl your hair and make your nerves jump and your skin itch. On nights like that every booze party ends in a fight. Meek little wives feel the edge of the carving knife and study their husbands' necks. Anything can happen." Such weather-behavior linkups wouldn't be much news to populations in Pacific Rim nations, the Middle East, and Europe. Germans are especially big believers. For more than a decade, Deutscher Wetterdienst, the German national weather service, has issued daily bio-wetter bulletins to the general public on the order of "cloudy with a chance of migraines and damp with a chance of insomnia." Similar bulletins are headed for your local weather forecast. The Weather Channel already broadcasts a daily "aches and pains index" in winter months. Weather Services International, the world's largest weather-news gatherer, has debuted a popular biometeorology page on its Web site, Intellicast.com. And at least three other major meteorological companies, such as Accu-Weather, are considering their own foray into weather-behavior forecasts. Can that be surprising in a nation in which more than half of all ill people use alternative medicine and herbal remedies? "Back in the 1980s, health stores were considered part of the lunatic fringe," says Joe D'Aleo, the meteorologist who launched Intellicast's weather-behavior page. "Now we run into our neighbors there. Americans are interested in anything that might promote better health." Still, the claims of biometeorology are difficult to confirm. Although medical conditions from angina and arthritis to hip fractures and dental periostitis have been statistically linked to weather, statistics alone are not proof of cause and effect. "I'd rank this stuff up there with the signs of the zodiac and old astrology texts," says Dr. John Renner, a family physician and president of the National Council for Reliable Health Information. "Put it this way: Would they be willing to ground a pilot or a plane based on the current evidence? Let's separate the hunches and impressions from the hard medical facts." Surprisingly, many biometeorologists agree. "We have--and I exult in this--the Missouri attitude: Show me!" says Dennis Driscoll, a biometeorologist at Texas A&M University. "I would like to see both doctors and meteorologists take the bit in their mouths, so to speak, and start doing some definitive research." But how? Designing such experiments is practically impossible. "I had one patient tell me, OThe frost is on the pumpkin and the pain is in my joints.' How would you test that?" says Terence Starz, a clinical professor of medicine at the University of Pittsburgh. "It would be too invasive. You'd be sticking measuring devices in peoples' joints." Similarly, Sharon Phelan, an obstetrician at the University of Alabama at Birmingham, has been present at births that occurred during times of falling barometric pressure. "Hurricanes, too, have been associated with the rupture of the amniotic membrane," she says, "but it's all anecdotal. A study with real patients? I don't know how you would do that." Well, there is the work of Michael Persinger. Locked in a steel chamber in the basement of a campus building in Sudbury, Ontario, a student sinks into a ratty brown chair, snuggles up with a blanket, and pulls on a yellow motorbike helmet studded with wires. Outside, Persinger, an American-born neuroscientist and clinical psychologist, sits at a computer screen directing a series of electromagnetic waves at his subject's temporal lobes. With a thousand tests already in the bag, he has assembled a repe rtoire of patterns that induce moods volunteers later describe in questionnaires as "mild euphoria," "low level fear or panic," "depression," or "drowsiness." "We're not sadistic here," Persinger says, "so most of the time it's pleasure." Persinger places his subjects in an acoustic chamber the size of a bank vault to block out other electromagnetic waves. The pulses he sends in are 1 microtesla, about as powerful as the magnetic field 10 centimeters away from a computer screen. Persinger believes not only that the pulses mimic subtle electrical signals carried by pre-storm air masses but also that such electromagnetic fields are forces the brain reacts to. "What tells a cell what to do? What affects chemicals and behavior? Electromagnetic patterns," he says. At Laurentian University, where Persinger has taught for 30 years, students joke about the prof's chamber of horrors, and he himself can't resist references to Dr. Frankenstein. Still, he is arguably this continent's preeminent biometeorologist. To him, it makes perfect sense that living things should be susceptible to weather-related stimuli. Researchers already concur that the absence of sunlight can trigger seasonal depression. And many accept the word of elderly patients who complain that wind, with its shifting sound waves, irritates them so much they'd rather stay indoors. But most physicians aren't likely to agree that gases released from soil during turbulent weather could affect their patients' moods. Or that Earth's magnetic fields could alter body chemistry. To Persinger, they're not just conceivable, they're probably measurable. In his behavioral neuroscience lab, students bombard rats with extremely low frequency (ELF) electromagnetic waves that mimic electrical charges carried in weather systems. Critics say such waves are too low in intensity to have any effect on humans. But Persinger insists it's not the waves' intensity that matters but their frequency and shape. Sooner or later, the body's autonomic nervous system, the bundles of nerves and fibers that control our bodies' internal workings, will respond to the faint but persistent barrage. Consider what happens at a typical cocktail party, says Persinger. When you enter a room filled with people talking, the voices sound loud at first, then as your hearing acclimates, the voices seem to mute: "If I'm talking to you and I raise my voice and RAISE IT AND RAISE IT, it gets so loud that you leave. If I whisper, though, you pay attention and you can understand what I'm saying." Whispers slice through background noise because they carry two pieces of information: the metamessage ("This is important") and the actual message ("Do this"). He believes extremely low frequency waves grab the brain's attention in much the same manner. Day and night, in tiny cinder-block rooms in Persinger's animal lab, furry, pink-nosed subjects scurry around Plexiglas cages wrapped with coils of blue wire like large electromagnets. In one experiment, rats were induced to attack their neighbors after exposure to extra low frequency waves. In another, rats with multiple sclerosis found their symptoms suppressed after electromagnetic bombardment. In still another experiment, rats first taught the location of food and exits in a maze were then exposed to magnetic fields for an hour. Placed back in the maze they couldn't recall any of their new skills. The results dovetail with biometeorological lore; for years adherents have claimed that weather events, such as approaching storms, can enhance or disrupt learning. In a 1997 study, Rod O'Connor, one of Persinger's students, found that the incidence of sudden infant death syndrome seems to be higher when geomagnetic storm activity is very low, with background frequencies of about 0.2 to 0.5 hertz. (Geomagnetic storms are caused by the compression and decompression of Earth's static field by solar winds.) Researchers have found that infants who die of SIDS have low levels of melatonin, a hormone that is best known for controlling our internal clocks but also mediates production of nitric oxide, a chemical transmitter integral to breathing. O'Connor believes that magnetic fields generated during weather events can depress nocturnal levels of melatonin and in turn, nitric oxide, disrupting infant breathing. To test his hypothesis, O'Connor has been exposing rat pups to weak magnetic fields of no greater than 0.5 hertz, similar to those that occur during geomagnetic storms. Pups exposed to the lowest intensity fields die soon after showing brain chemistry changes that reflect a drop in melatonin levels. Aside from Japanese and Norwegian public health officials requesting information, O'Connor's findings haven't generated attention. And that leaves the 28-year-old neuroscientist frustrated. "The big focus in sudden infant death syndrome right now seems to be on placing infants on their backs as a way to reduce the chance of death," he says. "That's a practical solution, but it doesn't explain the underlying mechanism of the trouble. The attitude is: OWhy look for anything else?' " As O'Connor well knows, biometeorologists learn early to put a lid on their own exasperation. History has not been kind to those who indict weather. The work of Chicago pathologist William F. Petersen, who in the early 1930s blamed the weather for changes in the blood clotting and white blood cell count of three patients, has been forgotten. A more dire fate befell Joseph Hollander's weather studies. The rheumatologist, who in the 1960s placed arthritic patients in a barometric chamber, included his findings in a textbook he edited. Rheumatologists still refer to the classic text, but the weather chapter has been neatly excised. And Persinger, who has been denied grants so often that he subsidizes his lab mostly out of his own pocket, is a bigger hit among TV producers seeking footage of his quirky experiments than he is with physician researchers. He jokes that medical acceptance of his theories and methods is like the weather: "It comes and goes." Other biometeorologists see the issue of acceptance differently. Laurence Kalkstein, a bioclimatologist at the University of Delaware and an expert on heat and human mortality, sticks to the provable: Heat kills. In 1995, with a grant from the Environmental Protection Agency, Kalkstein developed software that told officials in Philadelphia and Washington, D.C., when dangerous heat waves were on the horizon and how many people might die. He is doing the same for Shanghai and Rome, with grants from United Nations agencies. "I agree biometeorology has been through an identity crisis," he says. "But now it's gaining recognition." Biometeorology matters, Persinger says, because the way in which we order our lives in the 21st century leaves us especially vulnerable to weather insults. "Our indoor environments have become extraordinarily physically constant," he says. "The lighting. The temperature of our houses. One thing we do know about biological systems is that they tend to respond to contrast. And one of the things that fluctuates most these days is the weather." Today, if a huge low pressure system--one of the last forces humans can't control--comes screaming out of the west and squats over the eastern seaboard, in the two or three days when the mass is parked overhead, thousands of people will fight with their spouses, wreck their cars, give birth, and fail exams. No scientist can study such a sprawling matrix and convincingly pin the rap on weather. But Persinger envisions a day when people answer a daily Web-based questionnaire. With such data in hand, biometeorologists might then have a leg to stand on. And maybe we'd know for sure that our faults are not in our stars, but in the clouds. Forecasting Behavior Intellicast.com's biometeorology page reaps more than 100,000 hits monthly. Fans log on, just as they would to check the news or monitor their stocks, but they want to know if today's weather means they will be achy or likely to suffer a blinding headache, lose their concentration, or face slower reaction times. Pregnant women can check if they're likely to go into labor. There's little mystery to how the site generates its forecasts. Meteorologists program their everyday software to scan for a specific set of weather criteria, such as falling barometric pressure, increasing cloud cover, and high humidity. When the computer finds a location on the map that falls within the guidelines, it labels the area. But how good are the parameters? Some maps are more scientifically accurate than others. For example, the map depicting areas of high air stagnation is solid: Air pollution makes people sick. But mood charts? Reaction times? Birth and labor indexes? Where's this stuff coming from? To program the quirkier connections, Intellicast meteorologist Joe D'Aleo consulted Weather and Health: An Introduction to Biometeorology, a text published in 1969 by the late Helmut Landsberg, the University of Maryland professor many consider to be the father of modern bioclimatology. As a result, parts of the site can only be considered good clean fun. When it comes to the Labor Index (above), the computer is programmed to look for areas of falling atmospheric pressure. "The more precipitous the fall, the greater the number of full-term and near full-term pregnant women who experience labor pains," says the site. "Birth follows, often near the passage of the lowest pressure or associated fronts." There's little science to back up such statements. In a 1997 study, doctors at the University of Massachusetts Medical School compared maternity ward admissions with data from the Worcester, Massachusetts, station of the National Weather Service. Their conclusion: "Although there was an observed statistically significant association between falling barometric pressure and onset of labor, the magnitude of the difference is not of clinical significance." --J.D.

RELATED WEB SITES:

Visit the National Climatic Data Center in Asheville, North Carolina (www.ncdc.noaa.gov), or the Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey ( www.gfdl.gov), or the National Severe Storms Laboratory in Norman, Oklahoma, at http://www.nssl.noaa.gov.

Also read this month's feature story How dry we were? <feathowdry.html> ?

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