The Weather Notebook: Paleoclimatology

Paleoclimatology
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Nowadays, you can instantly get the latest weather anywhere in the world - but try finding out what it was doing in New York City on February 1, 1850 and you'll understand why atmospheric scientists are always grumbling about how short and sparse reliable weather records are. But thanks to recent strides in the field of paleoclimatology - the study of ancient climates - this is changing. Hi, I'm Dave Thurlow from the Mount Washington Observatory and this is The Weather Notebook.

By uncovering and analyzing traces and clues to earth's past atmosphere, paleoclimatologists have been able to reconstruct dramatic climate shifts, long-term warm and cold cycles, precipitation patterns, and in some cases specific weather events thousands of years into the past.

For example, fluctuation in the width and density of tree rings on 400-year-old bald cypresses in Virginia swamps suggest that a severe drought stressed the Jamestown Colony during the 1620s. In the desert Southwest, bristlecone pines growing or preserved on arid mountain slopes provide a record of local rainfall going back 8,000 years.

Even earlier climate data come from ice cores samples drilled in polar ice sheets and mountain glaciers. The presence of two different oxygen isotopes, which vary with temperature, as well as traces of dust, volcanic ash and carbon dioxide trapped in ancient ice allow researchers to chart climatic fluctuations going back 200,000 years. We still may not know whether it rained or snowed on Central Park 150 years ago, but using the evidence of paleoclimatology, we are assembling a clearer and more detailed picture of earth's climate through the ages.

Thanks to today's contributing writer David Laskin. Funding for The Weather Notebook comes from Subaru and the National Science Foundation.