Rising evaporative demand highlights India’s data and research gap

• Global warming has increased the air’s thirst, leading to more water coming off the land, including from plants and trees.
• The term “thirstwave” refers to three or more contiguous days of intense evaporative demand, which is increasing over the U.S.
• The researchers found that thirstwaves have grown more intense, more frequent, and lasting longer, especially in seasons when crops are grown.
• Evaporative demand is measured using standardised short-crop evapotranspiration, which is defined as the amount of water a grass surface 12 cm high will use.
• An increasing standardised short-crop evapotranspiration indicates the ambient temperature is increasing, the humidity is dropping, wind speeds are picking up, and the amount of solar radiation is picking up.
• The effect of humidity on evaporation and potential evapotranspiration has been found to nullify the effect of rise in temperature.
• Researchers from IIT-Roorkee, the National Institute of Hydrology, and institutes in France and The Netherlands reported recent changes in evaporative demand across 100 river sub-basins in India in 2022.
• There is considerable scope to investigate this phenomenon in the Global South, where societies are generally more vulnerable to the consequences of climate change.
• The worst thirdwaves happened in places that do not experience the highest [evaporative] demand, suggesting a need to reevaluate how governments prioritize different regions of their countries for climate change preparedness and climate mitigation.