Flavio Lehner

Climate scientist and assistant professor of earth and atmospheric science

Cornell University climate scientist Flavio Lehner, who has monitored water supply in the Southwest for about a decade, says while heat is the immediate health concern, we should also expect significant negative impacts on the already record-low snowpack.

Lehner says:

“The heatwave forecasted for the Western U.S. over the coming weeks is remarkable, with several temperature records expected to be broken. Generally, the Western U.S. is no stranger to strong and persistent atmospheric ‘ridges’, a pattern that diverts incoming Pacific storms to the North and sets up an area of high pressure with clear skies and accumulating heat in the Southwest. In a warming climate, any such event has the potential to be warmer than it would have otherwise been. 

“However, it is also possible that this type of event, that is, atmospheric ridging, has become more frequent over recent decades, which would explain the long-term trend towards drier conditions and reservoir depletion in the West. Our group published a study last year showing that this is indeed the case, due to a unique combination of greenhouse gas-warming and long-range effects from air pollution over East Asia. Whether this tendency will continue into the future is an active area of research. What is certain is that continued emissions of greenhouse gases will make heatwaves – irrespective of their origin – more severe. 

“While heat is the immediate health concern for this event, we should also expect significant negative impacts on the already record-low snowpack across much of the intermountain West. This snowpack is a vital natural water reservoir that sustains agriculture during the dry summer months. Barring a ‘Miracle May’ snow event, I wouldn’t be surprised if some junior water right holders will see curtailments this year.”