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
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 St 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 scientist 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 business-people 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 21 st century when and if [CO.sub.2] 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. Scientist 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 Nina. 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 `smoking 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, `You 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.”
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