Assessing the potential for crop albedo enhancement in reducing heatwave frequency, duration, and intensity under future climate change

Adapting to the impacts of future warming, and in particular the impacts of heatwaves, is an increasingly important challenge. One proposed strategy is land-surface radiation management via crop albedo enhancement. This has been argued to be an effective method of reducing daily hot temperature extremes regionally. However, the influence of crop albedo enhancement on heatwave events, which last three or more days, is yet to be explored and this remains an important knowledge gap. Using a fully coupled earth system model with 10 ensemble members, we show that crop albedo enhancement by up to ＋0.1 reduces the frequency of heatwave days over Europe and North America by 10 to 20 days; with a larger reduction over Europe under a future climate driven by SSP2-4.5. The average temperature anomaly during heatwaves (the magnitude of the event), is reduced by 0.8 °C to 1.2 °C where the albedo was enhanced, but reductions in mean heatwave duration are limited. There was a marked reduction in the mean annual cumulative heatwave intensity across most of Eurasia and North America, ranging from 32 °C to as high as 80 °C in parts of southern Europe. These changes were largely driven by a reduction in net radiation, decreasing the sensible heat flux, which reduces the maximum temperature, and therefore, heatwave frequency and intensity. These changes were largely localised to where the albedo enhancement was applied with no significant changes in atmospheric circulation or precipitation, which presents advantages for implementation. While our albedo perturbation of up to ＋0.1 is large and represents the likely upper limit of what is possible with more reflective crops, and we assume that more reflective crops are grown everywhere and instantly, these results provide useful guidance to policy makers and farmers on the maximum possible benefits of using more reflective crops in limiting the impacts of heatwaves under future climate.