Specific Objectives of the Project
The objectives of this research are to (1) quantify past adaptation to climate change in United States field crop production, (2) estimate the long-run consequences of climate change on this type of agriculture, and (3) assess the potential of one specific adaptation, double-cropping, to attenuate the potential losses resulting from climate change.

Project Report/Summary of Results
We have developed a theoretical framework whereby agricultural production is related to both contemporaneous weather and long-run climate through simple quadratic functions. The framework implies a long-run response function to climate that is the outer envelope of short-run responses to weather conditional on climate. Applying this framework to a 66-year panel of yields and weather, we simultaneously estimate short- and long-run responses to climate for the United States (US) corn sector. We find evidence of significant climatic adaptation. In the case of temperature exposure (captured through growing degree days), traditional “myopic” panel methods that do not explicitly model climate adaptation nonetheless deliver estimates similar to those of our estimated long-run response. We formally show that this is due to the large cross-sectional variation in climate temperature relative to locational weather fluctuations. In contrast, for precipitation, which exhibits larger year-to-year variation relative to cross-sectional variation, models that do not account for climatic adaptation deliver estimates that are biased, but can be viewed as an average of the long- and short-run responses.

In complementary work, we focus on one specific adaptive action: double cropping. Although prior agronomic research suggests that climate change may expand the area suitable for double cropping in the US, there is relatively little empirical evidence of the relationship between climate and farmers’ decisions to double crop. We link high-resolution land cover data with detailed soil and climate data to explain farmers' propensity to double-crop soybeans with winter wheat in the Eastern United States. We find small and slightly negative effects of warming on double-cropped acreage. A fixed-effects panel model of county yields further indicates that yields of double-cropped soybeans are about 9.9% lower than those of single-cropped soybeans. Accounting for both of these effects, we conclude that double cropping is unlikely to offset negative impacts of climate change on US crop production.