Atmospheric River

The document examines the paradoxical future of the western United States, where warming temperatures are projected to cause both more severe droughts and a higher likelihood of catastrophic megafloods. It highlights that while the total number of atmospheric rivers may decrease, those that do occur will be more intense due to the atmosphere's increased capacity to hold water vapor. Furthermore, warming is shifting precipitation from snow to rain, leading to declining snowpack volumes in the Northern Hemisphere and the American Cordillera, which complicates water management and increases flood risks.

• Climate change is increasing the probability of historic megafloods in California, similar to the Great Flood of 1861-1862. Research indicates that for every 1 degree Celsius of global atmospheric warming, the likelihood of such an event increases rapidly. Under a high-emissions trajectory, the probability of a megaflood more than triples by 2060, representing a "600 percent increase in risk".
• Warming temperatures are altering the nature of precipitation in the western U.S. by increasing the moisture load of atmospheric rivers and causing more precipitation to fall as rain rather than snow. While individual storms may become more intense, NASA research suggests the total number of atmospheric rivers bringing precipitation to the region may actually decrease, potentially exacerbating meteorological droughts.
• Snowpack volume is projected to decline across the Northern Hemisphere and the American Cordillera by 2100. This trend is linked to fewer days with freezing temperatures and a shorter snow season. These changes result in a shift in timing, with peak streamflow and runoff occurring earlier in the calendar year, which creates significant challenges for water management.
• The severity of future hydrologic impacts is heavily dependent on emissions pathways. In the western U.S., average annual spending on atmospheric river-related flood damage, which has been approximately $1 billion per year over the last 40 years, is projected to double under an intermediate-emissions scenario (RCP4.5) and more than triple under a high-emissions scenario (RCP8.5).

APA

Osenga, E. (2023). Atmospheric River. Energy Innovation. https://energyinnovation.org/expert-voice/atmospheric-river/

Chicago

Osenga, Elise. Atmospheric River. Energy Innovation, 2023. https://energyinnovation.org/expert-voice/atmospheric-river/.

Wikipedia

{{cite report |last1=Osenga |first1=Elise |title=Atmospheric River |publisher=Energy Innovation |date=30 March 2023 |url=https://energyinnovation.org/expert-voice/atmospheric-river/ |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{osenga2023atmospheric, author = {Osenga, Elise}, title = {{Atmospheric River}}, institution = {Energy Innovation}, year = {2023}, month = mar, url = {https://energyinnovation.org/expert-voice/atmospheric-river/}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }