Mark Bittman and IPCC on Yield Changes

Mark Bittman writes in April 2 NYTImes about the IPCC report with the theme the effects of climate warming

"So yields of corn and wheat are down and falling while prices are going up."

From an NPR interview with an IPCC scientist, who didn't concur with the final report:

"Take crop yields, for example. The report says climate change will cause them to fall by a few percent per decade. But Tol says technological innovation will likely raise crop yields by 10 percent or more each decade.
"So it's not that crop yields are going to fall, but they're going to rise more slowly because of climate change," he says. "And then of course it doesn't sound as alarming."

From the IPCC report.

Current economic studies of climate change that include farm- and/or market-level adjustments suggest that the negative effects of climate change on agriculture probably have been overestimated by studies that do not account for adjustments that will be made. This may be caused by the ability of the agricultural production community to respond with great flexibility to a gradually changing climate. Typically, extreme weather poses a significant challenge to individual farming operations that may lack the spatial diversity and financial resources of large, integrated, corporate enterprises with production capabilities in one or more areas.

Simulation modeling using four GCM-based scenarios showed that U.S. cereal production decreases by 21-38% when farmers continue to do what they are now doing (i.e., no adaptation) (see Table 15-4). When scenarios that involve adaptation by farmers are used, decreases in cereal production are not as large and the adaptations are shown to offset the initial climate-induced reduction by 35-60% (Schimmelpfennig et al., 1996; Segerson and Dixon, 1999).

And

When autonomous agronomic adaptation is included, crop modeling assessments indicate, with medium to low confidence⁶, that climate change will lead to generally positive responses at less than a few °C warming and generally negative responses for more than a few °C in mid-latitude crop yields.