USDA economist on the difficulties of climate modeling

Christine Stebbins in Reuters: Climate and food production is a subject that needs more study in coming years but for now even the U.S. Agriculture Department finds it almost impossible to estimate the effects of one on the other. "They are very elaborate models," said USDA's chief economist Joseph Glauber, referring to climate-crop forecasting in an interview on Tuesday on the sidelines of a farm lending conference at the Kansas City Federal Reserve.

"Take into account all the fundamentals on crops and yields. You also have to build in all this climate variability and predictions about climate variability. The range of potential outcomes is pretty large," Glauber said. "We just don't consider that in our 10-year baseline. We assume some trend growth, we really don't even look at variabilities. That's probably proper for a 10-year forecast horizon."

The USDA's crop reports, such as the monthly World Agricultural Supply and Demand Estimates (WASDE) and its 10-year baseline crop outlooks, are key benchmarks for the world food and farming industries, given the vast domestic and world data gathering the agency employs.

"To take our crop forecasting models -- they are what they are -- and try to marry in a lot of climate stuff, it's pretty cumbersome," Glauber said. "With climate comes looking at land use -- forest versus pasture versus cropland," Glauber said. "We are just beginning to see some of the modeling on that."

Glauber cited studies by the Intergovernmental Panel on Climate Change (IPCC) and the U.N.'s Food and Agriculture Organization (FAO) as important models to build upon. "Climate doesn't make a difference much over 10 years. There is a lot more variability now relative to say 10, 15 years ago. But the real changes we are talking about here start manifesting themselves over 30, 40, 50 years," Glauber said….

Corn field with people walking through cut stalks in 1993. Photo by Andrea Booher/FEMA Photo