1. The Science of Climate Change: Global and Local Perspectives Jim Steenburgh Department of Atmospheric Sciences University of Utah jim.steenburgh@utah.edu

2. “Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, [and] sea level has risen.” – IPCC (2013) NOAA/NCDC

3. “It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20 th century” – IPCC (2013) Steenburgh (2014), adapted from Knutson et al. (2013)

4. Utah 1993 2011 2012 1934 NOAA/NCDC

5. Western Snowpack Trends Pierce et al. (2008) SWE/P Fraction of winter precipitation retained in the snowpack on April 1 st

6. Future Projections Steenburgh (2014), adapted from IAMC RCP Database and Knutti and Sedlacek (2012)

7. Downscaled for Central Wasatch Courtesy Court Strong Moderate with StabilizationMitigation for 2ºC Moderate Growth High Growth Change from 30-year period centered on 1990

8. Vulnerability (Snowfall > 7000 ft) Steenburgh (2014), Courtesy Leigh Sturges Sensitivity greatest @ lower elevations Increasing competitive advantage for resorts with high elevation ski terrain

9. Downscaled Snowfall Trends Lute et al. (2015) Snowfall Water Equivalent (SFE) 1950–2005 to 2040–2069 High Emissions Scenario % Change SFE % Change Snow Days % Change Big Storms Colder Stations Warmer Stations

10. Summary Trends attributable to global warming are apparent over the West –Rising temperatures –Declines in low-elevation snowfall fraction and snowpack No clear trend yet in less sensitive upper-elevation snowfall fraction and April 1 st snowpack Although weather and climate variability will still produce year-to- year fluctuations, trends consistent with global warming will become increasingly apparent during the 21 st century –Rate of change remains a key research question Snowfall and snowpack sensitivity increases with decreasing elevation and mean wintertime temperature –Losses greatest at lower, warmer elevations –Major competitive advantage for colder, higher elevation resorts Utah/Colorado vs. most other US resorts (some exceptions) Alta/Snowbird/Brighton vs. other Wasatch resorts