Did Climate Change Cause US Drought?

Climate change may not have caused the record drought that set the U.S. Corn Belt ablaze last year. At any rate, this is what a report by five U.S. federal agencies, published Thursday, April 11, concludes.

The year 2012 was both the driest and hottest year in the U.S. since 1895, when weather record-keeping began. The lack of water was shown to be even more serious than during the Dust Bowl, the series of sandstorms that swept the Great Plains region between 1934 and 1936. More inclined to speak about the environment since his re-election, on several occasions, President Obama has demonstrated readiness to cite this dryness as proof of the climate change that threatens the country.

Natural Climate Fluctuations

However, the 20 scientists who participated in the study have refuted this analysis. According to them, a series of natural variations in weather, “a sequence of unfortunate events,” explain this catastrophe, which has caused losses of $20 billion, according to the U.N, and has sparked a rise in food prices.

Thanks to computer-generated simulations, scientists have been able to prove that humid air coming from the Gulf of Mexico was unable to shift north, as it does under normal weather conditions. As a result, the jet stream, which ordinarily transfers humidity from the Gulf, got trapped far away, north of Canada. Therefore, the country did not see any April or May spring rains, and July and August failed to bring their share of seasonal storms, while those that came nevertheless produced little rainfall.

“Neither ocean states nor human-induced climate change, factors that can provide long-lead predictability, appeared to play significant roles in causing severe rainfall deficits over the major corn-producing regions of central Great Plains,” the report concluded.

“The circumstances were so unusual the drought could never have been predicted.”*

Lead author Martin Hoerling, a research meteorologist at the National Oceanic and Atmospheric Administration, added:

“This is one of those events that comes along once every couple hundreds of years.”

A Partial Study

These astonishing conclusions did not foster unanimity in the heart of the scientific community. Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research, a university center financed by the federal government, told the Associated Press that the report does not take into account the lack of snow the Rockies had seen during the previous winter — caused by climate change — and the way in which this deficit had affected air humidity. Furthermore, it had not considered at all how global climate change had exacerbated the holding up of the jet stream the north of the U.S.

“This was natural variability exacerbated by global warming,” asserted Kevin Trenberth.

“That is true of all such events from the Russian heat wave of 2010, to the drought and heat waves in Australia.”

Another obvious point: The report is centered on six U.S. states — Wyoming, Kansas, Nebraska, Colorado, Missouri and Iowa — while drought has rapidly spread across the entire continent. During July, 61 percent of the area coverage of the U.S. was declared as being in a state of acute rain deficiency.

Debating Global Warming

This disagreement and the means used to produce such a government report, once again, prove global warming is real, even if the role man plays in this change still generates debate over the Atlantic.

No later than Wednesday, Texas Republican Joe Barton quite seriously argued for a “divergence of evidence” on the causes of global warming, taking the biblical flood as an example.

“I would point out that if you are a believer in the Bible, one would have to say the great flood was an example of climate change. That certainly wasn’t because mankind had overdeveloped hydrocarbon energy,” he declared during hearings on the controversial Keystone XL pipeline project, which would transport oil extracted from the tar sands of Canada to refineries in the Gulf of Mexico.

Nevertheless, scientific studies — notably ones originating in the U.S. — are showing it constantly: Monthly world temperatures lower than those in the mid-20th century have not been recorded on earth since February 1985. As a sign of ongoing warming, the 10 hottest Novembers since 1880 occurred during these last 12 years, while the 10 coldest Novembers all date from before 1920.

The consequences are the following: Extreme weather conditions, especially droughts, have multiplied in North America over the past 30 years and are expected to increase in the future, according to a study published in October by German reinsurance company Munich Re. Of its own accord, a U.S. study published in the journal Nature Climate Change in December warned against the probable loss of water reserves in the U.S. Southwest because of global warming.

*Editor’s note: The author seems to be quoting directly from how several news sources have paraphrased the report’s findings.