In this paper, we perform a comprehensive analysis of the impacts of climate change on winter wheat, one of the most widely planted crops, using data in China. We allow the climatic impacts to differ across seasons (growing stages) and regions with different climates in our panel data model. We find that heat in the fall and freezing days in the spring are the most evident drivers of yield reductions. We also find evidence of substantial adaptations in response to these damages. More importantly, our findings suggest that existing studies could have possibly overstated the climate change damages on winter wheat yields due to the omission of the potential benefit from the reduction of freezing days. For instance, our results indicate a yield reduction of 0.5% under a uniform 1 ºC warming scenario compared with a reduction of 3-5% found in existing studies, which is consistent with our results (a yield reduction of 5.5%) if the freezing effects were omitted in the model. The overestimation of climate change damages on winter wheat is robust to Shared Socioeconomic Pathway scenarios (SSPs) with which even yield gains are expected.

Surface ozone pollution has been proven to impose significant damages on crops. However, the quantification of the damages was extensively derived from chamber experiments, which is not representative of actual results in farm fields due to the limitations of spatial scale, time window, etc. In this work, we attempt to empirically fill this gap using county level data in the United States from 1980 to 2015. We explore ozone impacts on corn, soybeans, spring wheat, winter wheat, barley, cotton, peanuts, rice, sorghum, and sunflower. We also incorporate a variety of climate variables to investigate potential ozone-climate interactions. More importantly, we shed light on future yield consequences of ozone and climate change individually and jointly under a moderate warming scenario. Our findings suggest significant negative impacts of ozone exposure for eight of the ten crops we examined, excepting barley and winter wheat, which contradicts experimental results. The average annual damages were estimated at $6.03 billion (in 2015 U.S. dollar) from 1980 to 2015. We also find rising temperatures tend to worsen ozone damages while water supply would mitigate that. Finally, elevated ozone driven by future climate change would cause much smaller damages than the direct effects of climate change itself.