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Early vs. Late Snowmelt

This comparison is one illustration of how snow cover and the timing of snowmelt can vary from year to year. Winter’s snow has fallen by April and begun to melt, so one way to compare the timing of snowmelt in different years is to compare the extent of snow cover on the same April dates; this image compares 2002 and 2008 for April 7-14.

On average, snowmelt has been coming earlier and earlier to the American West in recent decades, in a trend that appears linked to warmer temperatures from climate change. The trends of warming and earlier snowmelt are projected to continue this century. As the comparison here illustrates, year-to-year natural variation means that we can still see years with late snowmelt, even if the overall trend is toward earlier.

The data for this image were generated by the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard a NASA satellite, and come by courtesy of the Cryospheric Sciences Branch of the NASA Goddard Space Flight Center.

See the related video, Washington: Warming and Wildfires.