"Future climate impacts of direct radiative forcing of anthropogenic aerosols, tropospheric ozone,
and long-lived greenhouse gases"
Chen, W; Liao, H; Seinfeld, J.H.
Journal of Geophysical ResearchPublished 26-July-2007
Presented by Jason EnglishJournal Club
26-September-2007
GHG and Trop. Ozone effect on climate
Climate Effects
Aerosol Effect on climate
Direct effectIndirect effect
Acid Rain (sulfates) Reduced VisibilityHealth Effects
Why are sulfate aerosols important?
Cause of Global Circulations
• Primary cause - uneven heating of the earth causes thermal wind, ocean-atmosphere coupling, Coriolis
• Can aerosols affect regional climate? If they affect global circulation, they might
Global aerosol RF: -0.5 W/m2
Asia aerosol RF: -10 to -50 W/m2
(includes natural)
Everything increases except sulfate, CFCs
A2 scenario: heterog. world, no sustainability, slow technology development - highest year 2100 CO2 and SO2 of all SRES scenarious
2 separate simulations with present climate use, 5 year integ. avg
•c
SO4
NO3
POA
•c
SOA
BC
O3
2000-2100 simulations
• Equilibrium climate used – GISS GCM, 4x5 resolution, 9 vertical layers, 1 hr time step– 80 yr integration; 50 yr spinup, 30 yr comparisons– This involves constant emissions and forcing– More pronounced differences than transient climate
• Aerosol RF– Internal mixtures– Refractive Indices parameterized from volume-weighted
mixing rule– Dry nitrate assumed same refractive index as dry sulfate– Gamma distribution SA-weighted dry r=0.3 um, variance=0.2– Mie theory applied to calculate extinction, SSA, g from
refractive indices and size distribution
•Overall, more energy into the system (TOA), but less directly to the surface
Change in RF 2000 - 2100
BC over snow,ice
Heating through most of the tropopause above the surface
Change in RF 2000 - 2100
Hot hot hot
Change in Surface T 2000 - 2100
BC over snow,ice
Scat.aerosols
Summer,fewerscat. aer.
High latitude GHG warmer due to ice-albedo feedbackHemispheric winter = more emissions
Change in Surface T 2000 - 2100
Change in Atmospheric T 2000 - 2100
Latent heat
•Aerosols weaken hadley cell DJF, strengthen it JJA
•GHG weakens hadley cell
Change in Streamfunction 2000 - 2100
baseline
Absolute humidity
relative humidity
AER & GHG cause increased evap in tropical lower trop = higher absolute humidity
Relative humidity controlled by Clausius Clapyron eqn
Excess precip change
convective precip change
AER hadley cell effect causes precip changes
GHG cause more heating = stronger convection
TOA SW flux
TOA LW flux
TOA SW flux affected by albedo and cloud cover changes
TOA LW flux affected by water vapor, clouds (GHG affects these)
Sea ice melting
More clouds
Surface SW flux
Surface latent heat
AER causes warmer air/cooler surface
GHG cause warmer air and surface
Surface sensible heat
•Why Asia? -> huge AER forcing
Regional WINTER Climate Change 2000 - 2100
•Aerosol composition change causes warming, Ozone causes warming, GHG cause warming….
Hot Hot Hot!
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