Climate Change – News and Comments
Maps of monsoon history
Brendan Buckley cores a tree in Vietnam. Photo: K. Krajick, Earth Institute, Columbia U.
“Asian Monsoon Failure and Megadrought During the Last Millennium” is the dramatic title of a report in Science that introduces a new Monsoon Asia Drought Atlas. Edward R. Cook and his colleagues at the Tree-Ring Laboratory of Columbia University’s Lamont-Doherty Earth Observatory have used tree-rings from 300 sites in Asian forests to reconstruct the summer “Palmer Drought Severity Index” (PDSI) across India, China and adjacent regions. PDSI is a fairly complicated reckoning of local deviations from mean conditions, originated in 1965 by Wayne C. Palmer, a climatologist in the US Weather Bureau.
In the following examples, North American data supplement the Asian PDSI, and anomalous sea-surface temperatures (SST) across the Pacific are also reconstructed.
On land, brown is abnormally dry, green is wet. On the oceans, red is abnormally warm, blue is cool. Fig. 4 in E.R. Cook et al, Science, 23 April 2010, distributed by NOAA Paleoclimatology.
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Climate Change: Updating The Chilling Stars
Monsoons and the Sun
Late rains saved most of the 2009 harvest of India, despite a shortfall of 21% in the summer’s rainfall that led to a ban on rice exports, after a 17% loss of production in West Bengal. But 2009 saw the worst deficit in India’s summer monsoon since 1972, while Burma (Myanmar) had its the shortest monsoon season since 1979.
It is chastening to recall that, in April 2009, Reuters reported the Indian Meteorological Department as saying, “IMD’s long range forecast for the 2009 south-west monsoon season (June to September) is that the rainfall for the country as a whole is likely to be near normal.” Even an updated forecast in June expected only a small rainfall deficit. Clearly, the unpredictable monsoons remain a problem for meteorology and climate physics.
Is there a link between reduced monsoon rains and the Sun’s recent sluggish behaviour, shown by the scarcity of sunspots? Probably. But to clarify the solar link well enough to make better regional forecasts, for even a few months ahead, remains an urgent task. Read the rest of this entry »