Recent Climate Change Modeling Results Eric Salathé Climate Impacts Group University of Washington

Global Climate Models 20th Century Validation

IPCC Scenarios for Pacific Northwest Climate Change 2-10 ºF ºF ºF

Range of Projected Climate Change for the Pacific Northwest from Latest IPCC Climate Simulations

21st Century Change

Shift in Pacific Storm Track Salath é, Geophys Res Lett, 2006 Observed 20th Century Model Composite 21st Century Model Composite

Downscaling

Empirical Downscaling Assumes climate model captures temperature and precipitation trends Quick: Can do many scenarios Shares uncertainties with global models Regional Climate Model Based on MM5 regional weather model Represents regional weather processes May produce local trends not depicted by global models Additional modeling layer adds bias and uncertainty Downscaling Methods Used in CIG Impacts studies

Mesoscale Climate Model  Based on MM5 Weather Model  Nested grids km  Nudging on outermost grid by forcing global model  Advanced land-surface model (NOAH) with interactive deep soil temperature

Potential Surprises How does loss of snowpack feed back on the climate? How do changes in the winds affect the local climate? Are their changes in cloudiness that can affect the local rate of warming?

MM5 Simulations ECHAM5 global model to force the mesoscale system to see how well the system is working , , Climate Change

1990s Validation Obs Record Max Obs Record Min Obs Mean Max Obs Mean Min MM5 Min Day of Year Temperature (°F) 1995 Daily Max and Min Temperature at SeaTac MM5 Max

1990s Validation Gridded ObservationsMM5 - NCEP ReanalysisMM5 - ECHAM5 January July Mean Surface temperature

Evaluation of Future Runs Because there are some biases in the GCM runs, results for future decades (2020s, 2040s, and 2090s) will be evaluated against the ECHAM5-MM baseline

Winter Warming 1990s to 2050s Temperature Change Difference between MM5 and ECHAM5

Loss of Snow cover and Warming Snow Cover ChangeTemperature Change

Consistent trend over 21st Century 2020s2050s2090s

MM5 Compared to raw Climate model 2020s2050s2090s

Spring 1990s to 2050s Temperature Change Difference between MM5 and ECHAM5

Pressure gradient and Cloud Pressure ChangeCloud Change

Trend over 21st Century 2020s2050s2090s

2020s2050s2090s MM5 Compared to Raw Climate Model

Winter Trends at Various Stations MM5 - ECHAM510 IPCC Models

Applications: Air Quality

Applications: Hydrology

Summary  Projected Pacific Northwest Climate Change  warming: 1/4 to 1 ºF/decade  Probably more warming in Summer than Winter  Precipitation changes uncertain – Possibly wetter winters and drier summers  Challenges  Deficiencies in Global model propagate to regional model  Biases from regional model  Mesoscale model simulates different climate signal from global model  Loss of snow amplifies warming in Winter and Spring  Increased cloud cover in Spring -- reduces effect of snow loss