Scientists at Tufts University (USA) have predicted that climate change could negatively affect crop yields, including wheat grown in China and the US. This is reported in an article published in the journal npj Climate and Atmospheric Science.

The researchers analyzed seasonal forecast data over the past 40 years, which were used to calculate statistically about rare events that are difficult to determine from historical records. This approach, called the Unprecedented Simulated Extreme Ensemble or UNSEEN, allowed scientists to estimate the likely frequency of heat extremes that exceed critical wheat growth thresholds.

Winter wheat crops begin their growth in autumn and are harvested the following summer, but in spring, during flowering, they depend on the optimum temperature. At temperatures above 27.8 degrees Celsius, plants begin to suffer from heat stress. At temperatures above 32.8 degrees Celsius, important enzymes begin to break down.

In the US Midwest, extreme temperatures that occurred about once every 100 years in 1981 now have a return period of once every six years, while in China the current return period is on the order of once every 16 years. This means that in the US Midwest, extreme temperatures that had a one percent chance of occurring in 1981 now have a 17 percent chance in any given year, while in China the chance has increased from one percent to six percent.

Previously, in the region of the United States called the Midwest, there were seasons in which temperatures that promote the breakdown of enzymes lasted four to five days. There may be seasons in the future when unfavorable conditions can last up to 15 days, which will be devastating to crops.