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Pollen provides ancient weather report.

Pollen provides ancient weather report

For allergy sufferers, pollen seems to exist for the sole purpose of making people miserable. But palynologists, who study pollen and spores, say the plant grains are nothing to sneeze at. Since pollen can survive in sediments and rock for thousands and even millions of years, it gives scientists a portrait of the plants that once covered an area. At the forefront of pollen science, a new study shows these tiny reproductive elements can provide a detailed record of climate fluctuations during the last Ice Age cycle.

Researchers from the Laboratory of Historical Botany and Palynology in Marseilles, France, report in the March 23 NATURE they they have compiled a 140,000-year-long climate history for eastern France based on pollen records for that region. They collected the fossil pollen from sediments that have built up over the last 140,000 years in a lake and a swamp.

The scientists created the climate history through a complex translation process involving several stages and mathematical techniques. First they gathered modern pollen samples from a variety of locales in Europe, North Africa and Siberia. Then, based on the different kinds of vegetation found in each sample, they defined a mathematical relationship between the pollen and the climate conditions for that particular area. Finally they matched the fossil pollen samples against the most similar modern ones. This process gives a continuous measure of temperature and precipitation conditions reaching back in time through the last Ice Age and into the previous interglacial period, which occurred roughly 130,000 to 115,000 years ago.

This type of record will aid researchers trying to understand why Earth has swung back and forth between cold and warm periods over the last several hundred thousand years. In the past, investigators have relied mainly on long climate records from deep-sea sediments and more recently from cores of the Antarctic and Greenland ice caps. The continents have provided far less long-term information.

Vera Markgraf, a palynologist from the Institute of Arctic and Alpine Research of the University of Colorado in Boulder, says the French study is important because "it shows that there are other words besides the deep-sea record that can help us understand how the clime has changed."

Palynologists have drawn climate information from pollen for a long time, but this is one of the most detailed continuous records ever made. Still, Markgraf and others caution that the methods used in the new study are so complex they could be problematic. "It becomes acrobatics and a little bit dubious after a while," she says, "because you're going through too many steps."
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Publication:Science News
Date:Apr 8, 1989
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