Plant Growth Article

EOSC 112: The Fluid Earth	Plant Growth Article
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Site Map EOSC 112 Homepage Announcements Lecture Summaries Lab Assignments Special Topics Course Syllabus Web Contact: Phil Austin Site created with Cheetah. Last updated: Dec 7 2001	Globe and Mail: Warming makes North a lot greener By ALANNA MITCHELL EARTH SCIENCES REPORTER Saturday, September 8, 2001 - Print Edition, Page A1 From Canada to Russia and China, the planet's northern half is becoming greener and the growing season is longer as global temperatures rise, says a study based on NASA satellite images. The study is considered to be highly significant because it was conducted over two decades. The extra warmth means that the forests and crops of the Northern Hemisphere -- important for the foodstuffs and economies of humans -- are increasing. The extra vegetation likely is spawned by the growing accumulation of carbon dioxide and other greenhouse gases in the atmosphere. That same increase in plant life could help suck carbon pollution out of the atmosphere, say the study's authors. But if that sounds like a case for the benefits of global warming, it's the opposite, said Robert Kaufmann, a professor at the Center for Energy and Environmental Studies at Boston University and an author of the research paper. The increased vegetation reveals a short-term benefit that will give way to devastation as temperatures continue to rise. "It doesn't mean that even warmer temperatures are going to make it even greener," Prof. Kaufmann said in a telephone interview yesterday, noting that global average temperatures continue to rise. "Everything could get browner." He used this analogy: If you put someone in a cool room that is being constantly and gradually heated, the person at first becomes more comfortable. At some point as the room grows hotter, the person becomes desperately uncomfortable. Eventually, the person dies. Since 1981, growing conditions in the Northern Hemisphere have improved, Prof. Kaufmann said. The area covered by plant life has not increased, but the densities of the growth have. Green, which shows up in NASA satellite pictures taken over the 20 years, is especially pronounced in woodlands and forests ranging from Central Europe to Siberia and the eastern edge of Russia. The data show that the growing season in Eurasia is about 18 days longer than it was when the research began in 1981. Spring begins about week earlier and fall arrives about 10 days later. These are startling changes over 20 years, the NASA précis of the research says. In North America, the growing season is about 12 days longer than in 1981. Much of the added green comes from eastern forests and the grasslands of the upper U.S. Midwest. The hitch is that temperatures are rising faster than at any time in the past 1,000 years or more, Prof. Kaufmann said. The most recent report from the authoritative Intergovernmental Panel on Climate Change, published this year, found that average temperatures worldwide could rise about two to six degrees Celsius over the next century. Plant life may not be able to keep up with such dramatic changes, Prof. Kaufmann said. Plants now thriving may migrate as environments become hostile. But they are unlikely to do so in time, he said. Plant migration would have an effect on the carbon cycle. While there are more plants absorbing the increased carbon dioxide than there were 20 years ago, that will reverse as temperatures rise further. There will be less greenery absorbing less carbon dioxide, leading to yet higher temperatures. The research analyzed 20 years of satellite data north of 40 degrees latitude, which is north of New York City, Madrid and Beijing. The full academic paper is to appear next week in the Journal of Geophysical Research. NASA released the précis yesterday.