Transcript Regional Climate Change in the Pacific Northwest

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
0.7-1.8 ºF
1.6-4.3 ºF
2-10 ºF
Range of Projected Climate Change
for the Pacific Northwest from
Latest IPCC Climate Simulations
21st Century Change
Shift in Pacific Storm Track
Observed
20th Century Model Composite
21st Century Model Composite
Salathé, Geophys Res Lett, 2006
Downscaling
Downscaling Methods Used in CIG
Impacts studies
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
Mesoscale Climate Model
 Based on MM5 Weather Model
 Nested grids 135-45-15 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
• 1990-2000
to see how well the system is working
• 2020-2030, 2045-2055, 2090-2100
Climate Change
1990s Validation
1995 Daily Max and Min Temperature at SeaTac
MM5 Max
Temperature (°F)
Obs Record Max
Obs Mean Max
Obs Mean Min
Obs Record Min
MM5 Min
Day of Year
1990s Validation
1990-2000 Mean Surface temperature
Gridded Observations
January
July
MM5 - NCEP Reanalysis
MM5 - ECHAM5
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-MM5
1990-2000 baseline
Winter Warming
1990s to 2050s
Temperature Change
Difference between
MM5 and ECHAM5
Loss of Snow cover and Warming
Snow Cover Change
Temperature Change
Consistent trend over 21st Century
2020s
2050s
2090s
MM5 Compared to raw Climate model
2020s
2050s
2090s
Spring
1990s to 2050s
Temperature Change
Difference between
MM5 and ECHAM5
Pressure gradient and Cloud
Pressure Change
Cloud Change
Trend over 21st Century
2020s
2050s
2090s
MM5 Compared to Raw Climate Model
2020s
2050s
2090s
Winter Trends at Various Stations
MM5 - ECHAM5
10 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
Shift to Northerly Winds
Change in Sea-level Pressure
Change in Surface Winds