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PRI's Environmental News Magazine

Global Warming and the Shifting Seasons

Air Date: Week of March 3, 1995

In the search for signs of global warming, many scientists are looking at measurements other than temperature. One new study has found that the start of seasons is shifting significantly in many places around the world. The researcher says this dramatic shift started at about the same time humans began pouring carbon dioxide into the atmosphere.

Transcript

CURWOOD: This is Living on Earth. I'm Steve Curwood. The world's diplomatic community will gather in Berlin later this month to plot out the next steps to be taken under the International Convention on Climate Change, better known as the Global Warming Treaty, signed in Rio in 1992. But as the officials pack their briefcases, there's new evidence suggesting that the climate disruptions long forecast by scientists may actually be underway. Among the most startling new studies is one which links growing amounts of carbon dioxide in the atmosphere to a global shift of the seasons. For years the consensus among atmospheric scientists has been that large amounts of carbon dioxide and other greenhouse gases dumped into the atmosphere by human activity will cause temperatures around the world to rise, perhaps by as much as 9 degrees Fahrenheit by the year 2070. In other words, the scientists agree, every time we ride in our gasoline cars or switch on a light powered by a coal-fired generator, or burn a forest, we're helping to heat up the earth. With this forecast have come dire predictions of surging sea levels and epidemics of drought and storms. But so far there is no consensus that human-caused global warming has actually begun. The average world temperature is up about a half a degree since we began changing the atmosphere at the beginning of the Industrial Revolution. But natural factors could explain that. So many critics who aren't scientists say global warming remains just a theory. Still, others say there are signs that human-induced global warming is upon us. They point to the concentration of the century's hottest years in the last decade, increasingly extreme weather around the world, and a slow migration of species towards the higher latitudes. And research currently under review for publication may link global warming to an enhanced El Niño effect in the Pacific Ocean, which has plagued California with floods and led to an unusually mild winter in the Northeast. Now, a provocative study has emerged that doesn't come form climatologists, but rather from the phone company. Dr. David Thompson is a math researcher at AT&T's Bell Labs in New Jersey. Dr. Thompson crunched an obscure set of numbers and found that beginning in the 1920s, the normally regular ebb and flow of the seasons began suddenly going haywire. He says, for example, the starting time of winter is out of whack in many spots around the globe.

THOMPSON: England, it's changed about 5 days. Paris is about 8. Now this winter there is getting later. San Francisco is 3 weeks. A lot of the American West and Canadian Prairies, it's over a week. And so on around the world.

CURWOOD: Dr. Thompson specializes in information technology. He develops mathematical models to separate unwanted noise from valuable data, the kinds of things you need to do for long-distance communication. Out of curiosity, Dr. Thompson decided to apply his models to average monthly temperature readings from weather stations in central England, records that date back more than 300 years. Because of a wobble in the Earth's axis, there's a normal drift in the average starting dates of the seasons, about a day or so every 60 years in a cycle that takes about 22,000 years to complete. And Dr. Thompson says the English records reflected that cycle until about 50 years ago. Suddenly, the rate of seasonal advancement rapidly picked up. Checking data from other parts of the world, Dr. Thompson found a similar effect, and he correlated it closely to a sudden burst in the amount of carbon dioxide being pumped into the atmosphere in the 20th century. Dr. Thompson's research doesn't prove that later winters are a result of human-induced global warming. But it does provide strong support for those who say the climate is changing today far faster than it has in natural history. Dr. Michael McCracken is director of the US Global Climate Change research program.

McCRACKEN: It's building a rather strong circumstantial case, even though it's hard to get really direct proof that would get everyone in the legal term beyond all reasonable doubt.

CURWOOD: And climate scientist Michael Oppenheimer of the Environmental Defense Fund says Dr. Thompson's study could be a preview of what it will be like to live with global warming.

OPPENHEIMER: The changing of the timing of the seasons could affect the way farmers deal with their crops. It could affect times of the year that previously were very pleasant, like mid-May in the eastern United States, which might now turn into being periods with extremely hot, and essentially sometimes unbearably hot weather. If you come back in 50 or 75 years, a world that's had changed timing of seasons and other similar changes will feel and look a lot different, and we think a lot less pleasant than the current world that we have.

CURWOOD: The buzz about shifting seasons has many people talking. But whether Dr. Thompson's research will catch the diplomat's attention remains to be seen. So far, the Climate Change Treaty has been little more than an agreement that global warming is a threat, which countries should make an effort to avert. But there are no strict requirements to limit the emissions of carbon dioxide or other greenhouse gases. A New York meeting in advance of this month's Berlin conference produced little change, and observers are predicting the Berlin meeting may go the same. Some say that's because global warming seems so abstract. Perhaps this intriguing bit of research from Ma Bell will prove to be their wake-up call.

 

 

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