July 2023 was the hottest month in earth's recorded history. Temperatures exceeded 100°F in parts of South America, where it is the middle of winter! The ocean water in one spot off the coast of Florida hit 101°F, which must be unpleasant for marine life.
Extreme heat has a detrimental effect on crop production, a fact well illustrated in this paper by Wolfram Schlenker and Mike Roberts. Once the temperature gets above about 29°C (84°F), yields drop precipitously. The further above 29°C, the lower the yield; the more days above 29°C, the lower the yield. Every 24 hours spent an additional degree above 29°C reduces corn yield by about 0.6%.
Schlenker and Roberts, along with numerous researchers before and since, quantify temperature exposure using degree days. To calculate degree days above 29°C, compute how many degrees above 29°C the temperature is on each day and then sum across days. There are other details (e.g., accounting for the fact that the temperature varies throughout the day). If you're interested in those, start by reading Section 4.2.2 here and follow the relevant links.
In 2021 and 2022, central corn belt states like Iowa, Illinois, and Indiana enjoyed high corn yields. These same states were hit hardest by the 2012 drought. States further to the northwest, such as the Dakotas and Minnesota were hit less hard by the 2012 drought, but had relatively low yields in 2021.
Source: ucdavis.edu
Photo Credit: istock-mailson-pignata
Categories: Iowa, Crops, Weather