Climate Change and Urban Areas

1
Regional Effects of Aerosol Emissions

• William D. Collins
• National Center for Atmospheric Research
• Boulder, Colorado USA

• Simulations of European aerosols for 20th Century
• Effects on aerosols on solar radiation over
  Europe
• Effects of aerosols on aspects of regional climate

2
Air Pollution over Great Britain
NASA,SeaWIFS
NASA,SeaWIFS
3
Configuration of the CCSM3(Community Climate
System Model)
Atmosphere (CAM 3.0) T85 (1.4o)
Sea Ice (CSIM 4) (?1o)
Land (CLM2.2) T85 (1.4o)
Coupler (CPL 6)
Ocean (POP 1.4.3) (?1o)

• CCSM3 is described in
• A forthcoming special issue of the Journal of
  Climate
• The Aug. 2005 issue of the Int. J. High
  Performance Comp.

4
Forcings in IPCC Runs with CCSM3
5
CCSM Estimates of Aerosol Forcing
? Change during 20th Century
6
Increase in Aerosol Optical Depth
7
Increase in Sulfate Carbonaceous Aerosol
Optical Depth
8
Change in Annual Solar Fluxes
9
Change in Annual Clear-sky Solar Fluxes
10
Change in Summer Clear-sky Solar Fluxes
11
Slab Ocean Experiments
Control
NoAero
Fc lt 0
F'c 0
Ac gt 0
A'c 0
Ic lt 0
I'c 0
Atmosphere
Atmosphere
Land
Land
Slab Ocean
Slab Ocean
12
Reduction in Surface Air Temperatures
13
Reduction in Boundary Layer Height
14
Reduction in Surface Sensible Heat Flux
15
Reduction in Cumulative Precipitation
16
Conclusions

• Aerosols have significantly affected the climate
  of western Europe.
• The affects include (separate from other climate
  change)
• Reduction in surface shortwave fluxes by up to 6
  Wm-2.
• Reduction in surface air temperatures by up to
  -0.7C.
• Increased stability of the boundary layer due to
  cooling of the surface and heating of the
  atmosphere above.
• Reduction in cumulative precipitation by up to 6
  cm per year
• Caveats
• These results do not include nitrate aerosols.
• These results do not include interactions of
  aerosols and clouds.