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2012 Drought Worse Than Dust Bowl Era & Unpredictable

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The extreme 2012 Central Great Plains drought was more intense than the Dust Bowl era droughts of the 1930s, according to a new federal assessment of the origins and predictability of the drought, released on Thursday. The team of 19 atmospheric scientists, led by the National Oceanic and Atmospheric Administration (NOAA), found that global warming may have played a relatively small contributing role by helping to make the drought slightly warmer, and hence drier, than it otherwise might have been. 

Temperature anomalies during July 2012, the hottest month on record in the U.S.
Credit: NOAA.

The biggest "proximate cause" of the drought remains unidentified, the report found, and it was most likely the result of random natural weather and climate variability. However, critics argue that the analysis left out many important factors, such as the unusually low snow pack leading up to the spring of 2012, and studies that show how global warming influences the odds of heat waves.

The period of May through August 2012 was the driest such period in the Central Great Plains since 1895, eclipsing the records set during the Dust Bowl era of the 1930s, the report found. The drought caused the largest single-year loss in corn production since 1866, and the full economic impact of the drought, which in many areas is still ongoing, has not been tallied yet, but is likely to be greater than $12 billion. 

The report was aimed at determining whether the drought, which climate forecasters failed to foresee, was in fact predictable. The conclusion: It is likely that forecasters would be just as blindsided if the same precursor conditions that existed in early spring 2012 were to present themselves again. 

“This report’s appraisal is of an extreme event having limited potential for skillful long-lead predictability,” the report said.

However, experimental techniques are being tested that could improve such forecasts in the future, the report said.

The report may leave more open questions than answers, given that it found that no known source of natural climate variability can shoulder most of the blame for the drought, nor can man-made global warming, which over the long run is projected to make droughts more likely in some parts of the U.S., particularly the Southwest.

The report found that the Central Great Plains drought was distinct from the drought that developed in late 2010 over the Southern Plains, rather than an extension of that event. The report identified the beginning of the Central Plains drought as May 2012, when Mother Nature suddenly shut off the spigot of moisture that typically flows northward at that time of year from the Gulf of Mexico, where it usually triggers beneficial rains across the nation’s breadbasket. 

With High Pressure dominating the region and banishing Gulf moisture to other parts of the country, Omaha, Neb. saw no rain at all during July of last year, and other locations across the drought region also saw little if any precipitation during what is typically a wet time of year, the report found. Even tornadoes steered clear of the Plains, with the least active July on record.

“High pressure is just bad news when it comes to producing rains in summer,” said Martin Hoerling, lead author of the report and a NOAA meteorologist, during a conference call with reporters.

According to the report, computer modeling showed that slowly evolving ocean cycles, such as El Niño and La Niña in the Pacific Ocean, as well as other cycles in the Atlantic Ocean, did not appear to play a significant role in causing the drought. During 2012, La Niña, which is a periodic cooling of equatorial Tropical Pacific Ocean waters, was eyed as a possible key contributor to the drought, but this report casts doubt on that view. 

Instead, Hoerling said that unusually warm waters in the North Atlantic were “suspicious” since some research shows this can favor drought in the Plains. The report also found that the likelihood of severe drought events in the Central Great Plains has increased during the past 10 to 15 years, in response to global sea surface temperature changes, but this is of limited use when making a forecast for an individual summer.

“There was a change in the large-scale, slowly evolving climate that made drought severity more likely” in the past decade or so, Hoerling said, but nothing that pointed to a severe drought in 2012 specifically. In order to determine whether climate change made the 2012 drought more likely to occur, scientists need to conduct a separate analysis, and so this report offers a somewhat limited perspective on the role of climate change in last year’s drought. Instead, the report mainly dealt with the immediate causes of the drought, which led the team to focus on short-term weather and climate variability.

Map of rainfall departures from average for July 2012 across the Central Plains.
Credit: NOAA.

However, the scientists involved in the report said the warming climate means that current and especially future drought events are likely to be hotter and more severe than historical events, and that this one may have been somewhat hotter as well. July 2012, for example, was the hottest month of any month on record in the lower 48 states.

The Texas drought in 2010-2011 was the most severe one-year drought in that state’s history, as well as the hottest, and the Texas state climatologist, John Nielsen-Gammon, has said that some portion of that extreme heat was likely due to the long-term warming trend. 

“Temperatures within the last couple of years have been nudging up against or exceeding those that occurred during the Dust Bowl drought of the 1930s,” said Richard Seager, a researcher at Columbia University’s Lamont-Doherty Laboratory and a contributor to the new report. 

According to Seager, the main factor that controls summer temperatures in the central Great Plains is the amount of precipitation that falls during the season. Wetter summers tend to be cooler than dry summers, and the variability in precipitation has helped mask the long-term warming trend from man-made global warming. 

To find that global warming signal in a particular summer in the Central Great Plains, Seager said, “You’re looking for a tree within a forest of natural variability.”

Kevin Trenberth, a researcher at the National Center for Atmospheric Research and a frequent critic of Hoerling's work, blasted the report's conclusions in an online commentary. "The question never addressed is what does global warming and human influences bring" to the High Pressure areas typically associated with extreme heat and drought events, Trenberth said. 

The report, Trenberth said, "fails completely to say anything about the observed soil moisture conditions, snow cover, and snow pack during the winter prior to the event in spite of the fact that snow pack was at record low levels in the winter and spring."

 

Arun Kumar, of NOAA’s Climate Prediction Center, which is responsible for issuing seasonal climate outlooks for the U.S., said that while climate change may be increasing the long-term risk of heat waves and drought, this knowledge is hard to translate into forecasting the probability of specific droughts in a particular region at a particular point in time. 

The bigger factor in seasonal climate forecasting, Kumar said, “is what natural variability is going to do.”

One thing about the report is especially noteworthy: meteorologists could not pinpoint an end to the drought, because it is still ongoing. As of April 9, about 51 percent of the lower 48 states is still experiencing some form of drought. 

Editor's Note: This story was updated on Friday morning to include the view of Kevin Trenberth, a scientist who was not involved in the NOAA report.

Related Content:
Drought Has Ties to La Nina, With a Global Warming Assist
Lack of Warning on Drought Reflects Forecasting Flaws 
The Top 10 Hardest-Hit States for Crop Damage
Ongoing Coverage of Historic Drought in U.S.
Scientists Seek Insights Into Outlier Drought Predictions
http://Extreme Weather 101: Drought & Our Changing Climate

Comments

By Camburn (North Dakota)
on April 11th, 2013

It should come as no surprise that there was not a AGW signal in the 2012 drought.  State climatologists had expected a drought type of occurrence for almost a decade before this one hit.

Most of the region presently has had ample winter rain/snow events to recharge soil moisture.  In fact, the eastern 2/3 of the “Corn Belt” is now wet.

Reply to this comment

By Eric Peterson (Front Royal, VA 22630)
on April 12th, 2013

There’s some support for North Atlantic warming (positive AMO) being associated with drought: http://www.pnas.org/content/101/12/4136.full It is contrary to what I thought which was that the Pacific ocean cycles (PDO and ENSO) would control the storm track and precipitation in the continental U.S.  In any case, AMO is positive right now: http://www.esrl.noaa.gov/psd/data/correlation/amon.us.data with the caveat that this is unsmoothed data.

Reply to this comment

By Steve Goddard (Fort Collins Colorado 80525)
on April 12th, 2013

The 1930s drought lasted for more than six years, making it much more severe than the 2012 drought.

Reply to this comment

By Mark (Minnesota)
on April 12th, 2013

Climate has warmed. All weather nowadays is influenced by a warmer climate—more energy in the earth’s climate system—than was there decades or centuries ago. The dice are loaded. More frequent extremes and more extreme extremes are becoming commonplace. 

The whole question “was the drought caused by global warming” seems misguided. And the headline does not correctly capture one of the conclusions: “global warming may have played a relatively small contributing role by helping to make the drought slightly warmer, and hence drier, than it otherwise might have been.” That’s different than “Not Significant.”

Reply to this comment

By John (Calgary, Alberta)
on April 12th, 2013

Mark Minnesota.

Wrong!

Reply to this comment

By hank
on April 12th, 2013

Kudos to Climate Central for having the courage to post an article on the NOAA report about the 2012 drought. I doubt that we will see any other major pro-AGW blog reporting on it.

Hank.

Reply to this comment

By aarontj (kansas city)
on April 12th, 2013

Now that we’ve got that settled, can we retract & forget about penalizing anyone who passes gas or owns a cow that does?  I’m sure some liberal group has targeted these scientists as “hateful and dangerous”.

Reply to this comment

By Dave (Basking Ridge, NJ 07920)
on April 12th, 2013

The fact that I find most striking is that the means for predicting a really massive drought like that of 2012, are currently unavailable even when it is almost on top of us.

Reply to this comment

By Andrew
on April 12th, 2013

Dave -

That’s what I find the most interesting, and disturbing, part of this as well. See the “Related Content” at the end of the story for pieces I’ve written on drought prediction efforts, in reference to the 2012-2013 event.

Reply to this comment

By Leslie Graham
on April 12th, 2013

Of course the report didn’t say anything of the kind but that won’t stop the deniers pretending it did.
Geez. The report says AGW may have contributed to the drought. It’s there in black and white.
AGW is an established scientific fact and has been for decades. There is no ‘debate’ about it.
Clutching at cherry-picked single paragraphs while ignoring the obvious just makes you look stupid and desperate.

Reply to this comment

By Dan (boulder city, nv 89005)
on August 18th, 2013

Giant headline about it being ‘Worse’ than Dustbowl era, and I just finished reading the ACTUAL
NOAA report, where its clear the dusbowl was a prolonged period of dryness without a break,
and we just had ONE really dry year, with low corn yields, and following it now (2013) we’re
going to have the largest corn harvest on record, in history, period.  This is Variability, NOT
worse than the dustbowl.  Misleading headline.  Leslie needs to read more than her religious
materials.  try burtrutan dot com and his ‘hobbies’  and the specific, comprehensive review
of ‘global warming’ DATA looking at the entire history of climate and C02 production on earth.
We are actually at one of the LOWEST points in geologic history, not the highest. Since human
habitation is such a short time period we think we are important.  Mount Pinatubo’s eruption dumped
more C02 into the air than all of mankind in our entire history.  one volcano. and plants suck it up.
During earths greatest periods of DIVERSITY C02 was 18 TIMES what it is now.
You are right, it is impossible to have an informed debate with uninformed people. Most ‘climate
changers’ firmly believe in it, but the long term data prove otherwise. They just don’t want to look.
Remember, 10,000 yrs ago ( a geologic blink of an eye) New York was under 2 MILES of ice.
I promise:  the cavemen didn’t melt it with campfires or gaseous expulsions.

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