Aridity and wildfires driving hazier Western US skies

As the Western US is projected to get dryer, research suggests a correlated increase in wildfire-derived aerosol loading. Yet the feedback between these factors and climate warming pose uncertainties in predicting future climate.

A new study detailing the the relationships between aridity, aerosol loading, wildfires and climate in the Western US was published this week in Environmental Research Letters.

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Through uniquely collaborative efforts, atmospheric scientists and hydrologists took long-term observations to show linkage between drought, wildfire and summertime aerosol loading at high elevation sites in the West. They found significant correlation of aerosol loading and aridity at sites in Arizona, Wyoming, Colorado, Montana and Utah. Additionally, summertime aerosol loading strongly and positively correlated with total fire area burned, but is primarily found in the Southern Rockies. When evaluating climate model performance, simulation estimates predicted aerosol optical depth increase due to wildfires at high elevation in the Western US. The study concludes there will be hazier skies in a dryer climate.

The Denver Post highlights that these findings complicate forest management policies. With recent years of wildfire suppression driving thicker forest, forest managers favor letting wildfires burn for their restorative benefits. This paper’s results reveal that how we manage forests in the Western US will have broader impacts on climate.

The new paper, “Impacts of increasing aridity and wildfires on aerosol loading in the intermountain Western US,” was led by A Gannet Haller of University of Utah. Two of the eight other co-authors were Noah Molotch and Bren Livneh of CU Boulder.