On December 21, 2021, EPA issued “Seasonality and Climate Change: A review of observed evidence in the United States.” The peer-reviewed report summarizes observed changes related to seasonality in the United States. It discusses how climate change affects the timing and nature of seasonal events and describes some of the implications of those changes.
The report does not discuss the extent greenhouse gas emissions or other factors may have caused the observed changes.
Warmer Winters, Earlier Snowmelt
Some of the key changes:
- All seasons have warmed in the U.S., with winter temperatures increasing by 3˚F since 1896.
- Snowpack has declined in the West, with peak snowpack 9 days earlier since 1982.
- Winter-spring flows from snowmelt are 8 days earlier since 1940.
- The average length of the growing season has increased by two weeks since 1900.
- The average heat-wave season for 50 major cities is 47 days longer since the 1960s.
The report identifies most effects as negative; it acknowledges some, such as longer growing seasons, may be positive.
To see EPA’s news release, which provides a link to access the report https://www.epa.gov/newsreleases/epas-new-report-shows-how-climate-change-influencing-seasonal-events-us-and-impacting