CHICAGO (DTN) -- Agriculture is adapting to changes in climate, but weather volatility from higher temperatures, shifts in precipitation and higher carbon dioxide won't be fading away, experts told farmers Thursday at the DTN/The Progressive Farmer Ag Summit.

Producers wanted to know whether changes in climate are cyclical or are influenced by the actions of people. Do people have a bigger influence as scientists and the media suggest?

"Yes and no," said South Dakota Climatologist Dennis Todey. "OK, I think part of this has to be a definitions issue. Part of what we talk about with humans on the changes, we are putting out (carbon dioxide). We are changing the land surface. We are changing a lot of things that affect the climate. Is that the driver for everything that is going on? No. There is still natural variability that exists in the system. That's why we have inner-annual variability. That's why we have short-term changes in patterns. There are short-term issues and there are longer-term changes. We can't escape what is happening long term. We can't hide from that, but there is still some short-term variability."

Charles Walthall, national program leader for climate change at the USDA Agricultural Research Service, agreed with Todey's assessment that there are natural cycles in weather that continue to occur. But growing global population and increasing energy usage are releasing more greenhouse gases into the atmosphere.

"It's changing the energy dynamics and we're pushing things beyond the natural cycle," Walthall said.

Walthall told farmers about some of the issues USDA is examining as part of an updated national study on climate change set to be released in 2013. Changes in temperature, precipitation and carbon dioxide will lead to adjustments in crop production, cropping patterns and raising of livestock, USDA research shows.

"That puts a lot of stress on human beings, crops, animals, equipment," Walthall said.

Other problems can come from additional carbon dioxide in the air leading to more invasive species, insects and pathogens. Weeds respond aggressively to higher carbon dioxide levels.

"We have not bred the variety of crops to take advantage of higher carbon dioxide in the atmosphere," Walthall said. "Weeds, in their genetic freedom, for a large part have. That's why we are seeing larger, stronger weeds and vines."

One ARS experiment looking at carbon dioxide levels in 2050 showed intense weed growth that took four times the volume of herbicides to control, Walthall said.

"My concern is, and the scientists' is, that these impacts are going to affect the costs of farming," Walthall said.

Yet other plants that grow rapidly because of carbon dioxide don't absorb the nitrogen they need for that growth. The plant grows without creating the nutrients needed for the plant to be a sustainable grazing grass.

"Rangeland managers and ranchers are concerned about this and wondering if they are going to have to provide supplemental nutrients to cattle out on the ranch," Walthall said.

The National Oceanic Atmospheric Administration came out earlier this year with an adjustment of average annual precipitation over the last 30 years. South Dakota saw a two-inch bump in average rainfall. A big change in precipitation has come with more fall rains in the Northern Plains states, making it difficult to plant in the spring. That is reflected in the high volume of prevented planting claims that plague the Dakotas.

"More of it is occurring in heavier rainfall events, which, from a production standpoint is not a good thing," Todey said. "More soil erosion, more soil loss, it doesn't improve your bottom line by adding more moisture if it's running off."

Walthall also touched on the lack of emphasis on erosion. "This is something that does not get enough attention from my perspective," Walthall said. "The high-intensity, short-duration events as we know have massive implications for erosion."

Walthall noted some western states are seeing an overall decline in snowfall, as well as earlier spring melts. That puts stress on reservoirs that normally release water at certain times of the year for both urban drinking use and crop production.

"It has massive implications for water supply, especially in the west," Walthall said.

In another temperature shift, climatologists began to see dew points in the 80-degree Fahrenheit range during the 1990s but didn't believe them at first. Now these are more regular occurrences, highlighting that temperatures are not cooling down in the evenings as expected. While daytime temperatures may not be getting any higher in the upper Midwest, the lows in the evening are moving upward, putting stress on crops.

Higher temperatures do stretch out the growing seasons in many areas of the country, but the weather variability also can lead to early frosts as well. Other crops are reacting adversely to the heat.

"Worldwide (there is a) reduction of rice yields and it is partially being attributed directly to higher temperatures," Walthall said.

The increasing variability means more risk for producers and potential crop failures as well. Right now there are no indications that the volatile weather patterns are going to subside. The trend leans toward warmer temperatures, heavier rain events and more year-to-year volatility and extreme weather.

In delving into the politics of climate change, Todey said a colleague had tried working with lawmakers to form a "weather caucus" for volatile weather events, but a few congressmen advised him to avoid "the c-word."

"A lot of this is policy but not science," Todey said. "We have gotten to the point we can't talk about science."

Chris Clayton can be reached at chris.clayton@telventdtn.com

(AG/CZ)

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