06 July 2007

Same Drought, Different Meanings

Without a doubt, much of the US (and other parts of N America?) is currently experiencing a severe drought, as shown in the plot below.

Much of the Southeast is experiencing moderate to extreme drought, regions of drought are suggested around the Great Lakes, and much of the Southwest also has severe to extreme drought (which I would guess extends into Mexico...)

An important question arises related to the issue of attribution of the droughts. The New York Times article says:

drought... in the Southeast ... is more unusual, producing conditions not seen in more than 50 years in some places, and longer in northern Alabama.

Much of the region, government scientists say, is suffering from a rare sharp dry spell, though they are reluctant to attribute it to climate change. “In terms of its intensity, this one is very severe,” said Donald Wilhite...

Those ever-responsible, cautious government scientists :-) ...

Meanwhile, at Climate Progress in these [1 2 3] stories, the general tone of the articles is more of an implication of climate change (although Romm argues that he does not explicitly say that...).

Are these droughts the result of 'natural' cycles or induced by climate change? The truth is that we don't know. There have frequently been very bad droughts in the past, and we have a somewhat limited understanding of inter-decadal oscillations and teleconnections that could drive such natural cycles. Similarly, we can certainly say that these observations are consistent with the hypothesis of global warming, but we won't have statistical certainty for a long while yet. A third, more realistic option is that there is some combination of the two factors involved.

How do we decide scientifically? When, as a society, do we say 'Enough is enough' and begin to act? How will we know when it is climate change?

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