Monday, April 26, 2010

[californiadisasters] Enduring a drought of Medieval proportions

Enduring a drought of Medieval proportions

Over the past three years, California's drought has painfully pinched farmers, forced some cities into tight water-rationing schemes, and driven the Legislature to pass a dramatic overhaul of water policy along with an $11 billion bond measure.

For all the pain and expense, though, we should consider ourselves lucky. At least it wasn't a 500-year drought.

That's what at last parts of California experienced during the "Medieval Warm Period," roughly from the year 800 to 1300. And the result on the ground, according to new tree-ring studies of the Sierra Nevada's giant sequoias published by a University of Arizona scientist, was something residents of the often-fiery north state can appreciate.

Thomas W. Swetnam's study found that massive fires burned through the sequoia forest every three to 10 years, according to a report by ScienceDaily. Flames touched any individual tree, roughly, every 10 to 15 years. The ancient old sequoias — they can live as long as 3,000 years — have endured a lot.

For skeptics of global warming, the Medieval Warm Period has become a debater's trump card. Playing it signals that, hey, the climate has fluctuated before, change is natural, so why worry?

It's true that the Earth's climate changes all on its own, but that doesn't mean our own activities can't speed change up or raise the baseline — making the next warm period the very warm period or even the scorching-hot period.

And peeks back into the past, as best we can understand it, might well show us what we can expect in the future. If the sequoia study is a guide, the trees will be fine, but life not be so pleasant for the people who live near them.


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