Pre-Columbian America was plagued by decades-long megadroughts

Anthony Watts writes at Watts Up With That

In the August issue of Physics Today, climate scientists Toby Ault and Scott St. George share a pair of startling research findings. Between roughly 800 and 1500 CE, the American West suffered a succession of decades-long droughts, much longer than anything we’ve endured in modern history. And statistical models suggest that, as the climate warms, such megadroughts are increasingly likely to return.

western-US-megadroughts

How can scientists be so sure about the duration and extent of droughts that happened long before the era of instrument-based precipitation records? As Ault and St. George explain, the annual growth rings of ancient trees contain a rich paleoclimatic record of precipitation and soil moisture patterns. The width of a tree ring gives clues as to how well nourished the tree was in a given year. The map shows four western US megadroughts predicted from tree-ring data.

Ring-width analyses provide the most complete set of data on past moisture levels. But researchers have other ways of determining those conditions. Here are four of them:

Underwater tree stumps
Archaeological artifacts
Sand-dune cores
Pollen-grain deposits

The Full article is HERE.

Here are some other views of the long-term drought;

Long Drought History

G10b Sac River Flow 30T

 

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