​High temperatures affect agricultural yields. Over time, global warming could become the main factor involved in their degradation. Yet most studies rely on agronomic crop models that do not adequately describe the effect of high temperatures.

As part of an international collaboration, scientists from LSCE have shown that a set of nine models accurately depicts the temperature responses of US maize, soybean and wheat yields. In the absence of irrigation, for every day above 30° C, the growth indicator for maize and soybean plants drops to 6%. In the presence of irrigation, however, no significant decline was observed, either in the fields or in simulations.

This supports the hypothesis that the "real" culprit is water stress related to high temperatures. For wheat, a drop in yields at high temperatures was observed neither in experiments nor in simulations under real conditions, because the temperature during plant growth remained below the critical value.

In the future, the yields of all three cereals will drop for as long as the temperature consistently exceeds 30° C. An increased CO2 emissions rate will only slightly reduce yield losses, unlike irrigation.