Weather Change, Yields and Climate

April 2, 2013 08:40 PM
Weather Change, Yields and Climate

By Monica Burchett

Prepare for yields to oscillate with the climate

A crystal ball that predicts the weather would be nice, but forecasters have to rely on technology and records instead. A look back at the past three decades shows a trend toward increased volatility that climatologists believe will continue for the next 25 years, says Elwynn Taylor, an Iowa State University Extension climatologist.

The weather makes or breaks a crop. Climatologists call the late 1950s through 1973 the "benign years" because yield variability from year to year was negligible due to a consistent climate. From 1980 to 1996, yield volatility took a jump. In 2012, the Corn Belt experienced the first widespread drought since 1988 and the worst yields since the flood of 1993.

"We’ve had four 18-year periods of steady yields and four 25-year periods of erratic yields," Taylor says. "We don’t know the reason for the alternation, but they were curiously consistent, leading us to suspect that 2012 was the first year of 25 volatile years."

Indiana State Climatologist Dev Niyogi says frost dates are changing, which extends the growing season. "Temperatures will be slightly more than in the past," he says.

Gene Takle, director of the Climate Science Program at Iowa State University, is more specific, saying the growing season will lengthen by approximately 11 days by 2040, with locations warming faster in the north than in the south.  

An extended growing season doesn’t worry Taylor, but higher nighttime temperatures do. Plants develop during the day and night, so warmer nighttime temperatures hasten crop development.
"A nighttime warming of 4° in rice reduces yield by 20%," Taylor says, noting that corn shows a similar effect.

In July and August of 1994, nighttime Corn Belt temperatures were cooler than normal and crop yields were up. The following year, weather conditions were more favorable than in 1994, but yields were markedly less. Analyst’s attribute the lower yields in 1995 to warmer than usual July nights.

During the next 30 years forecasters expect more stress from too much or too little water. Overall, meteorologists believe average precipitation amounts won’t change much, but rain showers will be less frequent and heavier.


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