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Oceans combine to change U.S. weather patterns

Several factors contribute to changing weather patterns. La Niña events result in Texas drought. Adaptability is key for agriculture success.

A combination of warming water temperatures in the Atlantic Ocean and changes in the Pacific Decadal Oscillation (PDO) pattern (which shifts heat and energy to different parts of the world) is creating more extreme weather patterns and affecting food production.

In the Southwest, those changing patterns may mean extreme weather for the next 20 years and could mimic Texas weather of the 1950s.

In the near term, however, an El Niño event likely will bring colder temperatures and more moisture into the Southwest. “The longer an El Niño remains, the wetter it will be,” says Evelyn Browning Garriss, historical climatologist.

Garriss, speaking at the recent Beef Financial Management Conference in Amarillo, Texas, said this past summer’s unusual weather was shaped by unusual conditions, including eruption of two volcanoes — one in Russia and one in Iceland — as well as warming waters in the Atlantic, Pacific and Indian oceans. Also, prevailing winds carried heat into key production areas of the Northern Hemisphere.

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“We just broke nearly 2,000 heat records this summer,” she said. Lack of rain was not as big a factor as the heat, which increased evapotranspiration significantly. “The water supply couldn’t keep up. We had flash drought over 77 percent of the country.”

Garriss said the Atlantic Ocean controls Midwest weather. The Atlantic also features an oscillation factor — The Atlantic Multidecadal Oscillation (AMO). “When the Atlantic is hot, the corn fries.”

The two volcanoes also caused problems. “Eruptions altered the stratosphere and air pressure. Air pressure controls wind.” Volcanoes “trapped Arctic air well north. Fairbanks, Alaska, had 27 feet of snow; we had a warm winter.”

Garriss said that unusual occurrence — two volcanic eruptions in a year — is “very odd, a one-, two- or three-century occurrence. We don’t expect a repeat this winter.”

When a volcano erupts it shoots debris into the air. If it shoots high enough, debris goes into the stratosphere. “When it’s quiet, debris may remain there up to seven years and water collects and creates particles.” At some point, those particles create clouds, which block sunlight and affect weather patterns.

The Pacific climate also causes significant weather changes. “We had a cold La Niña for two years,” Garriss said. “It was a relatively small La Niña. But the colder water changed air pressure. La Niña equals a Texas drought.”

El Niño developed quickly. “Conditions developed for an El Niño five months after La Niña finished,” she said. “It usually takes two years.”

An El Niño also affects tropical storms. “It drives tropical moisture away from the Western Gulf. El Niño kept Hurricane Isaac weaker. Isaac carried a lot of moisture into the Midwest, too late for corn, but it helped soybeans and provided moisture for winter wheat planting.” Without El Niño, Isaac could have developed into a much stronger storm.


Weather affects commodity prices

The anticipated El Niño should bring “ideal agricultural conditions,” to the Southern Plains and into South America, she said. “Brazil and Southern Argentina should have great crops, which could drive down the price of corn.”

Garriss said weather change favors some areas and harms others. With the current PDO changes and warmer water to the East, moisture moves into Canada and the United States. “From the mid 1970s to the late 1990s, the United States and Canada enjoyed the most benign combination of the PDO and AMO.”

Weather winners and losers emerge from the oscillation changes. Winners include the United States’ Midwest, Northern and Central China, India, Japan, Southern Africa, Eastern Australia and Brazil. Losers include the Andes Republics and Argentina, California and the Southwest United States, Southern China, Pakistan, East Africa, Western Australia, and North Korea.

“La Niña weather patterns magnify the effects of a cold PDO,” Garriss said. “Also, prices go up with La Niña.”

In the 1960s and 1970s, corn prices were low. In 1975, prices rose when the PDO changed. “The pattern holds for wheat, corn and soybeans but not for rice, which is a tropical crop. La Niña sends prices up.”


Food availability

Climate changes also affect food availability, she said. “That’s particularly hard on developing countries. In the United States, farmers can rotate crops. Countries such as Pakistan are slower to adjust. It’s easier to change with a good agriculture infrastructure, such as we have in the United States.”

Texas should be well-positioned with infrastructure to deal with drought. “Texas has the best drought infrastructure of anywhere in the United States,” Garriss said. That advantage is based on the large number of reservoirs built in the 1950s. But those lakes have silted in to some extent. “Many are full of silt. They need to be cleaned out. And Texas needs to be more water conscious, especially with low levels in the Ogallala aquifer.”

As an historical climatologist, Garriss depends on “thousands of years of records,” to help understand weather patterns. “We have a sizeable database,” she said. That database includes tree rings, coral, sediment, and glacial cores, as well as historical records.

She cited the Herring Factor, a phenomenon observed for centuries by Scandinavian fishermen who noted when herring returned to the fishing waters. An early return meant southern waters were warming.

The database also shows significant effects on plant life when temperatures change. “Tree rings in North America show that small changes in temperature result in major changes in precipitation,” she said. “And a warm year may have significant implications on the water supply of the western United States.”

A 1 degree Celsius drop in global temperature, she said, is also significant and “moves the freeze zone 300 miles.”

The earth’s climate also adjusts according to the amount of solar radiation it receives and where that solar radiation falls. Cloud cover and volcanic debris can affect where radiation settles. Where solar radiation is stored — the oceans or the urban heat islands — also affects climate.

Garriss said the sun follows a seven-year cycle of activity. “It was quiet from 2007 through 2009. It’s beginning to wake up and should peak in 2013.”

Climate change from natural causes “ebbs and flows,” she said. “We need to adapt to its patterns.”

The alternative is to remain vulnerable to those ebbs and flows — periods of extreme drought alternated with periods of near normal or above normal rainfall, and fluctuation from extreme heat to unusual cold.

Farmers and ranchers should initiate management systems that allow for crop rotation, herd size alterations and market strategies that take advantage of price jumps that come with extreme weather.

Weather changes, Garriss says, such as changes in the PDO phase, alter “rainfall patterns. This creates difficulty for farming, particularly traditional farming.”

Successful farmers and ranchers adapt.

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