For most, to find evidence that recent years' droughts have been record-breaking, they need not look past the withering garden or lawn. For Henri Grissino-Mayer he looks at the rings of trees over the past one thousand years. He can tell you that this drought is one of the worst in the last 600 years in America's Southwest and predicts worst are still to come.
Grissino-Mayer collaborated with a team of scientists led by Park Williams of Los Alamos National Laboratory and others from the U.S. Geological Survey, University of Arizona and Columbia University to evaluate how drought affects productivity and survival in conifer trees in the Southwestern U.S. Their findings are published this month in "Nature Climate Change."
Tree rings act as time capsules for analyzing climate conditions because they grow more slowly in periods of drought and the size of rings they produce vary accordingly. Widely spaced rings indicate wetter seasons and narrow rings indicate drier seasons.
"Using a comprehensive tree-ring data set from A.D. 1000 to 2007, we found that the U.S. has suffered several 'mega-droughts' in the last 1,000 years in the Southwest," said Grissino-Mayer. "But the most recent drought that began in the late 1990s lasted through the following decade and could become one of the worst, if not the worst, in history."
... "We have nothing comparable in the past to today's environment and certainly tomorrow's environment," Grissino-Mayer said. "With increasing drought stress, our forests of tomorrow will hardly resemble our forests of yesterday."...
Dead Great Basin Bristlecone Pine in the White Mountains, California, shot by Velela, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 2.5 Generic license
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