Co-author: Ian Sue Wing, Dep. of Earth and Environment, Boston University, 675 Commonwealth Ave, Boston, MA

This paper assess the impacts of climate change on the productivity of four major crops across the world while accounting for the role of adaptation. High-resolution data on agricultural maps, crop calendar, dams and the associated reservoirs are paired with fine-scale weather data to describe crop exposure to temperature and precipitation between 1961 and 2010. By exploiting the unique time and spatial dimension of this database, the paper characterizes the pattern of crop yields over the full distribution of temperature and precipitation by climatic areas, distinguishing between irrigated and rainfed areas.

Guided by the more accurate description of crop exposure across climatic regions, we distinguish the short-run response to weather from the long-run response to climate. The estimated long-run semi-elasticities of crop yields to temperature and precipitation are used to assess the potential impacts of climate change in the Representative Concentration Pathway RCP 8.5, as simulated by the GFDL-CM3 climate model.

We show that short- and long-term responses can differ significantly, in both directions. The negative long-term impacts of temperature above 30°C can be of an order of magnitude greater than short-term effects. The benefits from precipitation can become larger over time, the more so if irrigation capacity is available. Daily average precipitations below 5-15mm/day or above a 50-55mm/day can be damaging for crop productivity, especially when irrigated areas are excluded.  The increased frequency of hot days is particularly harmful in temperate areas, where that would represent a greater shock compared to past average conditions. Rice is
the main grain that responds negatively to high temperature in tropical regions, despite being mostly irrigated. Our results suggest that globally cereal production declines, with higher reduction rates for rice and wheat.