investigation of the u.s. warming hole and other adventures in chemistry-climate interactions
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Running head for JAL’s first atmos chem paper. Investigation of the U.S. warming hole and other adventures in chemistry-climate interactions. Loretta J. Mickley - PowerPoint PPT PresentationTRANSCRIPT
Investigation of the U.S. warming hole and other adventures in chemistry-climate
interactions
Loretta J. MickleyPattanun Achakulwisut, Becky Alexander, Tom Breider, Bryan Duncan, Rynda Hudman, Daniel Jacob, Jennifer Logan, Shannon Koplitz, Eric Leibensperger, Lee Murray, Justin Parrella, David Rind, Lulu Shen, Dominick Spracklen, Amos Tai, Shiliang Wu, Xu Yue, and Lei Zhu
Running head for JAL’s first atmos chem paper.
2009 wildfire in Southern California
2013 ~1:1 ratio
1977 1 in 50
OzonePM2.5
Millions of people in US living in areas in violation of the EPA standards.
What is climate penalty on air quality? How will size of bars change with changing climate?
How do trends in short-lived species affect global and regional climate? Regional forcings are as large as global forcings from well-mixed GHGs.Short-lived species can affect methane lifetime.
1990 2001
Calculated trend in surface sulfate concentrations
Observations in circles
-2 Wm-2
Leibensperger et al., 2012
Atmospheric Chemistry
Assimilated meteorologyGEOS-4GEOS-5
GEOS-Chem
Atmospheric ChemistryLand cover model
GEOS-Chem
Meteorology from freely running climate model
Fire prediction model
Chemical feedbacks
Model frameworks1. Standard
2. Chemistry-climate
1. Examine observed sensitivities of short-lived species or other variables to meteorology.
E.g. Area burned = f(meteorology)
2. Apply sensitivities to archived meteorology from an ensemble of models.
Some methods to overcome uncertainties in model apparatus.
Yue et al., in review
Area
bur
ned
(105 h
a)
R2 ~ 0.5
Area burned over Southwest
model
observed
Area
bur
ned
(105 h
a) Timeseries of area burned
observed model3. Benchmark chemistry-climate interactions in the recent + distant past with observations.• Arctic 1980-2010• Last Glacial Maximum • Equatorial Asia 2000sArea burned in Southwest US may double by 2050.
Observed US surface temperature trend
GISTEMP 2010
Is the U.S. “warming hole” a signature of cooling due to anthropogenic aerosols?
Observed spatial trend in temperatures, 1930-1990
No trend between 1930 and 1980.
Warming trend after 1980
Contiguous US-1
1
0
o C1-1
We applied decadal trends in anthropogenic aerosol to the GISS climate model.
Increasing sulfate from 1950-1990s.
Decreasing sulfate beginning in 1990s.
1950 1960
1970 1980
1990 2001
Leibensperger et al., 2012a
Calculated trend in surface sulfate concentrations
Clearing trend in particles over United States since 1980s suggests possible recent warming.
Circles show observations.
Leibensperger et al., 2012a.
Direct radiative forcing
Indirect radiative forcing
Forcing from US anthropogenic aerosols peaks in 1980 -1990s.
Forcings over Eastern US
Peak forcings -2 W m-2, mainly from sulfate.
Warming from black carbon offsets the cooling early in the record.
Results suggest little climate benefit to reducing black carbon sources in US.
CLeibensperger et al., 2012b
Cooling from U.S. anthropogenic aerosols during 1970-1990.
Results are from two 5-member ensembles, with and without US anthropogenic aerosols.
Cooling is greatest over the Eastern US and North Atlantic.
1 oC cooling at surface over East
D Model Temperature 1970-1990
C
D Soil moisture availabilityD Cloud Cover
%%
Cooling over U.S. is not co-located with aerosol burden.
Cooling over North Atlantic strengthens Bermuda High, increasing onshore flow of moisture from Gulf of Mexico.
Local changes in cloud cover and soil moisture amplify the cooling effect.
Results are controversial.
Inclusion of US anthropogenic aerosols improves match with observed trends in surface temperatures over the East.
Most of the warming from reducing aerosol sources has already been realized.
• Results suggest that US anthropogenic aerosols can explain the “warming hole.”
• Warming since 1990s can be attributed to reductions in aerosol sources.
Leibensperger et al., 2012b
Observations
Model without US aerosols
Standard model
Eastern US
U.S. BC emissions (Tg
C)
1850
U.S.
SO
2 em
issio
ns (T
g S)
1900 1950 2000
BC
SO2
Timeseries of US emissionsHow have competing trends in BC and SO2 over 20th century affected regional climate across mid-latitudes?
Ongoing work.
BC aerosol• warms mid- to upper
troposphere• cools surface• stabilizes atmosphere
SO2 cools surface, may augment stabilization.
We will compare model BC with lake core sediments from Adirondacks (Husain et al., 2008)
BC d
epos
ition
(g m
-2 a
-1)
1860 1940
obstobservations
model
Deposition in Adirondacks
Leibensperger