We Don?t Know if Global Warming Is Causing Droughts

We don't know whether global warming is causing the droughts seen around much of the United States this summer

Photograph by Scott Olson/Getty Images.

?Everyone knows? that you should drink eight glasses of water a day. After all, this is the advice of a multitude of health writers, not to mention authorities like Britain?s National Health Service. Healthy living now means carrying water bottles with us, sipping at all times, trying to drink our daily quota to ensure that we stay hydrated and healthy.

Indeed, often we drink without being thirsty, but that is how it should be: As the beverage maker Gatorade reminds us, ?your brain may know a lot, but it doesn?t know when your body is thirsty.? Sure, drinking this much does not feel comfortable, but Powerade offers this sage counsel: ?You may be able to train your gut to tolerate more fluid if you build your fluid intake gradually.?

Now the British Medical Journal reports that these claims are ?not only nonsense, but thoroughly debunked nonsense.? This has been common knowledge in the medical profession at least since 2002, when Heinz Valtin, a professor of physiology and neurobiology at Dartmouth Medical School, published the first critical review of the evidence for drinking lots of water. He concluded that ?not only is there no scientific evidence that we need to drink that much, but the recommendation could be harmful, both in precipitating potentially dangerous hyponatremia and exposure to pollutants and also in making many people feel guilty for not drinking enough.?

The drink-more-water story is curiously similar to how ?everyone knows? that global warming only makes climate more extreme. A hot, dry summer (in some places) has triggered another barrage of such claims. And, while many interests are at work, one of the players that benefits the most from this story are the media: the notion of ?extreme? climate simply makes for more compelling news.

Consider Paul Krugman, writing breathlessly in the New York Times about the ?rising incidence of extreme events? and how ?large-scale damage from climate change is ? happening now.? He claims that global warming caused the current drought in America?s Midwest, and that supposedly record-high corn prices could cause a global food crisis.

But the United Nations climate panel?s latest assessment tells us precisely the opposite: For ?North America, there is medium confidence that there has been an overall slight tendency toward less dryness (wetting trend with more soil moisture and runoff).? Moreover, there is no way that Krugman could have identified this drought as being caused by global warming without a time machine: Climate models estimate that such detection will be possible by 2048, at the earliest.

And, fortunately, this year?s drought appears unlikely to cause a food crisis. According to the Economist, ?price increases in corn and soybeans are not thought likely to trigger a food crisis, as they did in 2007-08, as global rice and wheat supplies remain plentiful.? Moreover, Krugman overlooks inflation: Prices have increased six-fold since 1969, so, while corn futures did set a record of about $8 per bushel in late July, the inflation-adjusted price of corn was higher throughout most of the 1970s, reaching a whopping $16 in 1974.

Finally, Krugman conveniently forgets that concerns about global warming are the main reason that corn prices have skyrocketed since 2005. Nowadays 40 percent of corn grown in the United States is used to produce ethanol, which does absolutely nothing for the climate, but certainly distorts the price of corn?at the expense of many of the world?s poorest people.

Bill McKibben similarly frets in The Guardian and The Daily Beast about the Midwest drought and corn prices. Moreover, he confidently tells us that raging wildfires from New Mexico and Colorado to Siberia are ?exactly? what the early stages of global warming look like.

In fact, the latest overview of global wildfire incidence suggests that, because humans have suppressed fire and decreased vegetation density, fire intensity has declined over the past 70 years and is now close to its preindustrial level.

When well-meaning campaigners want us to pay attention to global warming, they often end up pitching beyond the facts. And, while this may seem justified by a noble goal, such ?policy by panic? tactics rarely work, and often backfire.

Remember how, in the wake of Hurricane Katrina in 2005, Al Gore (and many others) claimed that we were in store for ever more devastating hurricanes? Since then, hurricane incidence has dropped off the charts; indeed, by one measure, global accumulated cyclone energy has decreased to its lowest levels since the late 1970?s.?Exaggerated claims merely fuel public distrust and disengagement.

That is unfortunate, because global warming is a real problem, and we do need to address it. Warming will increase some extremes (it is likely that both droughts and fires will become worse toward the end of the century). But warming will also decrease other extremes, for example, leading to fewer deaths from cold and less water scarcity.

Similarly, there are real health problems?and many of them. But focusing on the wrong ones?like drinking a lot of water?diverts our attention from more important issues. Telling tall tales may benefit those with a stake in the telling, but it leaves us all worse off.

This article was originally published by?Project Syndicate.?For more from?Project Syndicate,?visit their new?Web site, and follow them on?Twitter?or?Facebook.

Source: http://feeds.slate.com/click.phdo?i=7df73e1121af0c40998474009857cb8c

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