Atmospheric River

This briefing, based on research from the Aspen Global Change Institute, examines the impact of climate change on atmospheric rivers and snowpack in California and other mountainous regions. It highlights a paradoxical future where the region faces both an increased risk of catastrophic megafloods and a long-term decline in snowpack and overall precipitation frequency, emphasizing that high-emissions scenarios will accelerate these hydrologic shifts.

• Climate change is increasing the probability of historic megafloods in California. Research using the ARkStorm 2.0 disaster scenario indicates that for every 1 degree Celsius increase in global atmospheric temperatures, there is a rapid increase in the likelihood of a megaflood similar to the Great Flood of 1861-1862. Under a high-emissions trajectory, the probability of such an event more than triples by 2060, representing a 600 percent increase in risk.
• While individual atmospheric river events may become more intense due to warmer air holding more water vapor, the total number of these storms bringing precipitation to the western United States may decrease. This creates a future characterized by fewer water-providing storms but more extreme precipitation when they do occur, exacerbating meteorological droughts.
• Global snowpack is projected to decline and shift in timing over the next century. In the Northern Hemisphere, warmer climate scenarios are linked to thinner, less widespread snowpack by 2100 and a shorter snow season. In the American Cordillera, including the Sierra Nevada, low-to-no-snow trends could emerge as early as 2025. These changes result in earlier runoff and peak streamflow, complicating water management.
• The economic impact of atmospheric river-related flood damage in the western U.S. is heavily dependent on emissions pathways. While average spending on such damage has been approximately $1 billion per year over the last 40 years, this figure 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} }