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​​​​​​​​​Long-Range Forecast

June 2, 2016

Keith Cherkauer is an engineer, ​not a meteorologist. He can't tell you if it will rain tomorrow. That's weather. But Cherkauer, an expert in hydrology at the Purdue Climate Change Research Center, thinks he knows what kind of conditions Midwest farmers will be facing in a hundred years.

"A lot like 2015, with wet springs and hot, dry summers," he says.

That's climate—how conditions develop over a long time.

In 2015, extreme weather events widely attributed to climate change were headline news. Globally, it was the warmest year in history, breaking the record set just the year before. Deadly heat waves were reported in India, Pakistan, Iraq, Iran and throughout Europe; floods in Ghana and Myanmar; droughts in Brazil and California. Unprecedented and unpredictable weather roiled agricultural markets and raised fears of a potential long-term threat to the global food supply.

Back home, Indiana had its wettest two-month period on record in June and July, followed by near-drought conditions in August and September. Fields that were flooded in spring were parched by late summer.

Farmers increasingly are finding that they have either too much water or not enough of it.

"We need to be planning for water use," Cherkauer says. "The question is, how do we better manage our water resources?"

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Weather and Climate

Weather patterns can change noticeably over short periods, especially in years such as 2015 when strong El Niño or La Niña systems add to the atmospheric instability. Climate change happens gradually and almost imperceptibly to untrained observers.

Researchers say the trend is real and unmistakable.

"The climate is already changing," says Jeffrey Dukes, Purdue professor of forestry, natural resources and biological sciences and director of the Climate Change Center. "Temperatures have increased quite a bit over the last century or so. Precipitation is changing, too."

It isn't just the amount of precipitation, it's how—and when—it's falling. Dukes expects the number of significant precipitation events—more than 2 inches of rain or snow at a time—to double or triple over the next 100 years, mostly in the winter and spring.

Extreme precipitation at planting time is especially problematic.

"With the warmer weather we are expecting, getting a longer growing season should be good," Cherkauer says. "But a lot of fields last year were left fallow simply because farmers could not get into their fields because of all the rain we had in the spring. If your tractor is sinking up to its axles in mud and you can't get your crops planted, you can't use that extra time."

The biggest deluge in 2015 came when crops should have been in their prime growing season.

Flooded field(Photo by Tom Campbell)

On July 7, central Indiana was hit by a storm that drenched the area with 4.43 inches of rain—about equal to the area's average for the entire month. For the month of July, Indianapolis recorded 13.14 inches of rain, a record and nearly 9 inches above normal.

"We're looking at more heavy rainfall events and longer droughts," Dukes says. "In the short term, the next 30-40 years, some crops may actually grow better. But the negatives are likely to start overwhelming the positives as time goes on."

Excess and Deficits

Mark Twain once said everybody talks about the weather, but nobody ever does anything about it. That's not entirely true. Farmers choose their crops and seed types based on the weather conditions forecast for the growing season. Investors establish market prices anticipating favorable or poor growing conditions.

Agribusiness professionals are accustomed to planning for weather variability from year to year. Now they might have to start dealing with more precipitation in the spring, which is already the wettest time of year, and even drier conditions in summer, when crops' water needs are highest.

Jane Frankenberger, Purdue professor of agricultural and biological engineering, is leading a five-year, $5 million federally funded project to determine how farmers could store water when they have it to use when they need it.

"Drained lands comprise at least 50 percent of Indiana's cropland, including some of the most productive lands in the state," Frankenberger says. "These can experience both water excess and water deficit in the same year, which is what happened last year. Storing drained water within the landscape could increase the sustainability of water for agriculture, particularly as intense rainfall and prolonged summer drought are expected to increase under future climate change."

Frankenberger and her team are looking at three specific practices: drainage water management to keep moisture in the soil longer and thereby maximize its effectiveness; saturated buffers to slow the outflow of water; and water recycling, in which subsurface drainage water is stored in ponds and then irrigated back onto the crops.

"There might come a day when farmers view excess water in the spring not as a waste to be disposed of but as a valuable resource to be saved in order to reduce the risk of water-stressed crops later in the season," Frankenberger says.

Modeling the Future

For now, it remains difficult to say when that day might come.

Researchers rely on climate and crop models to determine what the future will hold, but the recent rash of extreme weather has rendered many existing models obsolete. Scientists are working to develop new models that can account for unprecedented swings in climate.

"None of the current crop models are really good at extremes," Cherkauer says. "What we need to be working on is a future design that brings in resiliency and flexibility and accounts for what's happening in soil and streams."

All of this will have a noticebale impact on crops, Cherkauer believes, but there is no way to tell just yet what that will be.

"We'll likely see corn yields consistently reduced and soybeans generally higher," he says. "These might not be huge changes, but it's more like a 10-day weather forecast. We don't know the specifics, but our research can provide guidance on what to expect and how to make agriculture more resilient to climate extremes."