A look at weather extremes and the big-picture climate connections.

Six Images You Need to See to Understand the Drought

The U.S. is experiencing its worst drought in more than 50 years, and one of the top 10 droughts on record. In terms of drought extent and intensity, it is the worst drought since at least 1956, and has been compared to the devastating droughts of the Dust Bowl era during the 1930s, although those droughts were more intense. As of July 31, 62.91 percent of the lower 48 states was in at least moderate drought, down slightly from 63.86 percent on July 24. The Agriculture Department has taken the unprecedented step of declaring more than 50 percent of all U.S. counties as natural disaster areas, making them eligible for federal assistance to help struggling farmers.

What's causing this drought, why did it develop so quickly, and how bad is it, really?

Picture of the dried up Morse Reservoir in Indiana.
Credit: Twitpic/@Mikeseidel.

First, the causes. This drought developed due to a pronounced lack of rainfall, coupled with several unusual heat waves that struck during the spring and summer and helped to rapidly intensify the drought conditions. As you can see from this arresting image of the Morse Reservoir in Indiana, rainfall has not exactly kept pace with evaporation driven by the excessive heat. In fact, rainfall across the country has been well below average during the late spring and summer months in most of the lower 48 states. As Climate Central reported in July, the weather pattern that led to the drought may have had its roots in the tropical Pacific Ocean, related to a waning La Niña event.

This 16-second animation shows how quickly the drought intensified from late spring into summer, engulfing a large swath of the country.

The High Plains has been one of the driest areas of the country this year, with much below-average precipition and extreme heat, as can be seen in this colorful map from the High Plains Regional Climate Center. Unfortunately, the colors that farmers and ranchers want to see — greens and blues, indicating slightly above average precipitation — are almost nowhere to be found.

Percent of normal precipitation for the year-to-date, ending on August 1.
Credit: High Plains Regional Climate Center.

Although natural climate variability, such as a La Niña event that only recently dissipated, likely contributed to the drought, very warm temperatures have worsened the situation. This is the country's warmest year-to-date, with much of the nation broiling for most of the summer under the influence of a massive "Heat Dome" of High Pressure. The heat did not cause the drought, according to drought specialists, but it hasn't helped matters, since it accelerates the drying of soils and vegetation, thereby damaging crops.

In the exceedingly dry state of Oklahoma, Tulsa and Oklahoma City recorded back-to-back August days with a high temperature of 112°F. In Oklahoma City, this was the warmest it has been since the Dust Bowl, and just 1 degree shy of the city's all-time high temperature record. As you can see from this next map, the heat bullseye has been squarely focused on Oklahoma during late July into early August.

Temperature departures from average during the end of July into early April. Note the extreme heat centered over Oklahoma and northern Texas.
Credit: High Plains Regional Climate Center.

July was a particularly brutal month for farmers in the High Plains, as high temperatures were at or above 95°F nearly every day of the month. According to the U.S. Department of Agriculture, such high temperatures can damage corn and soybean crops.

The number of heat damage days when temperatures reached or exceeded 95 degrees during the month of July.
Credit: USDA.

As you might expect, soil moisture is running very low across much of the U.S., thanks to the 1-2 punch of the lack of rainfall and the heat. The soil moisture image below comes from the NASA GRACE Satellites, which detect small changes in the Earth's gravity field caused by the redistribution of water both on and beneath the land surface.

Surface soil moisture content as of July 30, 2012, as measured by NASA's GRACE Satellites.
Credit: NASA.

You can catch up with all of Climate Central's drought coverage, and read my earlier installment of exploring the drought through geeky weather maps. Please comment and offer suggestions of questions you'd like to see us tackle as the drought stretches into early fall, as well.

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By Bonnie Crawford (Oxford, MS 38655)
on August 4th, 2012

Do Republicans really believe that there is a drought?

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By labman57
on August 4th, 2012

Time for Rick Perry and his fellow climate change-denying, Bible-thumping politicos to call for another prayer meeting.

The climate change denial mindset is an outcome of a larger phenomenon that has become a fundamental component of conservative ideology lately—anti-intellectualism.

Fundamentally, climate change deniers refuse to accept the conclusions of the vast amounts of data gathered over many years by thousands of climatologists representing dozens of academic institutions, government agencies, and private sector interests from many nations—data suggesting a causal relationship between global warming and manmade activities. Their reasons for denial are purely of a political nature, but since they don’t accept the conclusions, they must also deny the veracity of the data for no other reason than it conflicts with their denials.

The fossil fuel industries that are financing the “climate change denial campaign” share the same unethical “profit at all costs” philosophy that has dominated the decision-making process of the tobacco industry as it repeatedly denied any health-related consequences of using their products.

In other words, climate change denial is a conclusion in search of a rationalization.

Record heat waves. Record flooding. Record blizzards. Record tornados. Record droughts. Record wildfires.  Record permafrost thaws and ice sheet melting.
Welcome to the new normal.

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By Dave (Basking Ridge, NJ 07920)
on August 4th, 2012

Please comment and offer suggestions of questions you’d like to see us tackle as the drought stretches into early fall.

Ok, I’ll bite.

How about one basic theme for questions along the lines of - the history, context and implications of US droughts, past, present and future?

The fact that technically this drought is starting to be seriously compared with the 1930’s dust bowl event is striking. However, I have heard that that event lasted for seven years or so.  In this case, this is year one and the drought may break with everything going back to normal next year and the year after. Let’s hope so. But what if it does not?  I think that question needs to be asked and answered. Is our only option to sit around and just cross our fingers? What are the implications of a two year drought? Three year? Etc.

As part of this, I would for instance be very interested to know:

1. In what ways is this drought different from and similar to the historic 1930’s dust bowl event and how are major droughts like that one and now this one categorized both technically and in terms of socio-economic impacts?  Is there a basis for determining the timescale category of the current drought, i.e. is it a 50 year event set to become a possible 100 year event, and what does that mean anyway?
2. Is there any data (historical, tree ring data, paleo record, etc.) available that clearly establishes the long range frequency and severity of significant droughts in North America over the past 1000 years or so?
3. What other regional weather events are now occurring elsewhere in the world that are, or are suspected of being, interconnected with conditions that are also producing this particular drought?  For instance, is the current encroachment of the Sahara desert into vast regions of sub Saharan Africa also related to this?  Is anything unusual happening in the desert regions in the US?
4. Are there any means by which farmers can better utilize advanced irrigation techniques or similar to better safeguard crops through future US droughts such as these?  Or is that an expensive and losing battle and if so is our food chain now becoming ever more prey to the Monsanto’s of the world with their genetically engineered, drought resistant, pest resistant and possibly eventually digestion resistant strains of cereal?
5. What is the current range of opinions within the general public about this drought and its relationship to climate change and how concerned or engaged is the general public with this issue, perhaps by region, where, the congress in Washington DC might represent a reasonable zero baseline for statistical comparison?

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By j. bollinger (Prompton)
on August 5th, 2012

Thanks. These maps really helped me make sense of what’s happening in the heartland.

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By Ray Duray (Bend, OR 97791)
on August 14th, 2012

Dear Andrew,

Terrific job on explaining the facts of the drought. With regard to future coverage of the topic, I think Dave from Basking Ridge has hit upon many of the questions I’d like to see addressed.

In addition, I think it would behoove us to start to pay a lot more attention to groundwater depletion in agricultural areas. The situation in Georgia (the state) is getting quite dire regarding groundwater. And recently Harper’s Monthly magazine ran an article about the mining of fossil water in the Ogallalla Aquifer that appears to be quite non-renewable with the projection of a massive return to dryland farming on the High Plains.

I think we need to prepare for some wrenching dislocations in our formerly abundant food supply in the U.S.

Another topic I’d like to see discussed is that if the conditions experienced in America’s grain belt this year become the new normal, what are the prospects for relocation of our major farming effort to the North? Climate-wise, this might seem obvious, but I fret about the soils up in the boreal forest and whether or not they’ll be able to sustain any large scale grain farming efforts? Perhaps that’s more of a soils science question rather than a climate question, so I’ll leave it to you whether or not you’ll ponder this prospect for adapting to a changing world.

Thanks again for a marvelous article, I look forward to reading much more of your output in the future.

Cordially, Ray

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