Transcript PPT - Atmospheric Chemistry Modeling Group

Investigation of chemistry-climate
interactions, with a closer look at the U.S.
warming hole
Loretta J. Mickley
Eric Leibensperger, Xu Yue,
Daniel Jacob, Jennifer Logan
David Rind, GISS
Jed Kaplan, U Geneva
2009 wildfire in Southern California
Millions of people in US live in areas with unhealthy
levels of ozone or particulate matter (PM2.5).
Number of people living in areas that exceed the national
ambient air quality standards (NAAQS) in 2010.
PM2.5
24-hour average or
annual average
Ozone
daily maximum
8-hour average
Bars on barplot will change with changing emissions.
Climate change could also change the size of these bars, by changing the dayto-day weather.
Particles affect solar radiation directly…and also indirectly by
modifying cloud properties.
California fire plumes
Pollution off U.S. east coast
Light-colored particles reflect sunlight
and cool the earth’s surface.
Black carbon
Aircraft contrails and cirrus over Europe
cooler
3
SO2 -- sulfur dioxide
NOx -- nitrogen oxides
Life cycle of particulate
matter (PM, aerosols)
precursor gases
ultra-fine
(<0.01 mm)
nucleation
Soup of
chemical
reactions
fine
(0.01-1 mm)
. . coagulation
.
. . .
condensation
Organic
carbon
SO2
NOx
SO2
NOx
VOCs
combustion
volcanoes
NOx
VOCs
cloud
(1-100 mm)
cycling
coarse
scavenging
(1-10 mm)
Black
carbon
VOCs
VOCs
NH3
VOCs -- volatile
organic compounds
NH3 -- ammonia
NOx
NOx
agriculture
biosphere
wildfires
combustion
dust
sea salt
4
Model frameworks
1. Standard
Assimilated meteorology
GEOS-4
GEOS-5
GEOS-Chem
Atmospheric Chemistry
2. Chemistry-climate
Chemical
feedbacks
Meteorology from freely
running climate model
Land cover
model
Fire prediction model
GEOS-Chem
Atmospheric Chemistry
Climate change
Air Quality
• Wildfire in the western United States in
the mid-21st century
• Consequences for air quality.
Rim fire, Yosemite Natl Park, 2013
Effects of wildfires on air quality in cities in Western US can
be very dramatic.
 Hayman fire, June 8-22, 2002
 56,000 ha burned
 30 miles from Denver and Colorado Springs
Unhealthy air quality in Denver
June 8, 2002
PM10 = 40 μg/m3
PM2.5 = 10 μg/m3
June 9, 2002 PM10 = 372 μg/m3
PM2.5 = 200 μg/m3
Standard = 35 µg/m3
Colorado Dept. of Public Health and Environment
Vedal et al., 2006
Fire activity had a big impact on
California air quality in 2013.
Timeseries of 3-hour average PM2.5
concentrations in Foothills Area
PM2.5 (mg m-3)
Rim Fire
Hazardous levels > 250 mg m-3
Very unhealthy
Aug 28
August 20
August 31
Will fire change in the future climate?
Unhealthy air
Aug 30
Very unhealthy air
Observations suggest that fires are increasing in North America.
obs temperature
area burned
5 yr means
1960
Area burned in Canada has
increased since the 1960s,
correlated with temperature
increase.
Gillett et al., 2004
2000
Increased fire frequency over the
western U.S. since 1970,
related to warmer temperatures
and earlier snow melt.
1970
2000
Westerling et al., 2007
IPCC AR4 models show increasing temperatures across North
America by 2100 in A1B scenario.
D Temperature JJA, oC
Models show increases of JJA
temperatures of ~ 3K in Western US.
D Precipitation JJA, %
Number of models showing
increased precipitation.
most
models
Results for precipitation changes are
not so clear.
few
IPCC, 2007 models
How do we predict fires in a future climate?
We don’t have a good mechanistic approach for modeling wildfires.
Start with the past.
Relationship between observed
meteorology + area burned
+
Future
meteorology
2 approaches
Future area
burned
Use ensemble of
climate models to
gain confidence in
prediction.
JJA Temperature
increase by 2100
Regression approach.
Regress meteorological variables and fire indexes onto annual mean area burned
in each of six ecoregions with a stepwise approach.
RMF
ERM
PNW
NMS
CCS
DSW
Ecoregions are aggregates of those in
Bailey et al. (1994)
Identify the meteorological
variables and fire indexes that
best predict area burned.
Include lagged met variables.
For example,
Area burned in Nevada/ semi-desert = f ( + T summer max that year
+ RH and rainfall previous years)
Best predictors: Temp, RH, precip, Build-up Index, Drought code, Duff
moisture code.
Predicted fires match observed area burned
reasonably well. Least best fit is in Southern
California.
RMF
PNW
NMS
CCS
Obs
Fit
Area burned in many ecoregions depends on
previous year’s relative humidity, rainfall, or temp.
ERM
DSW
Yue et al., 2013
Start with the past.
Relationship between observed
meteorology + area burned
+
Future
meteorology
Future area
burned
Use of an ensemble of 15 climate models
improves confidence in the results.
Changes in 2050s climate in the West.
• Temperature increases 2-2.5 K.
• Changes in precip and relative humidity
are small and not always robust.
Next step: apply meteorology from climate
models to the two fire prediction schemes.
Yue et al., 2013
Wildfire area burned
increases across the
western United States by
the 2050s timeframe.
Results from regressions approach.
Shown are median results.
Yue et al., 2013
Relationship between observed
meteorology + area burned
+
Future
meteorology
Future area
burned
Predicted area burned shows large increases in 2050s during
peak months.
Units = 104 hectares
future
present-day
X4 increase
X2 increase
Yue et al., 2013
How will changing area burned affect air quality?
Ensemble of
climate models
Median area
burned
Emissions = area burned x fuel
consumption x emission factors
Future
meteorology
GEOS-CHEM
Global chemistry
model
Future air
quality
Organic particles increase in future atmosphere over the
western U.S. in summer, especially during extreme events.
D Organic Carbon, OC
Cumulative probability of daily mean
concentrations of OC, Rocky Mountains
May-Oct
Ma
2050s
doubling
JJA
Presentday
Change in summertime mean organic PM2.5
in ~2050s, relative to present-day.
Wildfires may swamp efforts to regulate air
quality in future.
Yue et al., 2013
What do these increases in wildfire aerosol mean for
human health?
% area
burned
% OC
particles
Ongoing project with Yale will look at health
impacts of these increases.
Yue et al., 2013
How will wildfire change in a changing climate in Canada?
Ratio of 2050s area burned to present-day
Alaska Boreal
Cordillera
Ratio of 2050s area burned to present-day
Area burned increases in
the West due to:
• Higher temperatures
• More frequent blocking
high pressure systems.
Increased rainfall in Central
and eastern Canada blunt
these effects.
Ecoregions West to East
Yue, in progress
Aerosols
Climate change
• Regional climate effects of 1950-2050
trends in US anthropogenic aerosols.
Pittsburgh, 1973
What caused the U.S. warming hole of the 20th century?
Observed US surface temperature trend
1
No trend between 1930 and
1980.
0
Warming trend after 1980
-1
Contiguous US
Observed spatial trend in
temperatures, 1930-1990
-1
1
oC
GISTEMP 2010
Clearing trend in particles over United States
since 1980s suggests possible recent warming.
Calculated trend in surface sulfate concentrations
Increasing sulfate from
1950-1990s.
1950
1960
1970
1980
Decreasing sulfate by 2001.
Circles show
observations.
1990
2001
Leibensperger et al., 2012a
We first perform a pilot study:
Constant aerosols vs. zeroed US aerosols
Spin-up
Constant aerosols everywhere
GISS climate
model
Zeroed US aerosols, constant elsewhere
2010
A1B scenario of
greenhouse gases
2050
Forcing due to aerosol removal over US
Model setup causes large
warming over East.
By comparison, global DF
from CO2 is +1.8 Wm-2.
Results from pilot study:
Removal of aerosol sources over US increases annual mean surface
temperatures by 0.5 o C.
Warming due to 2010-2050
trend in greenhouse gases.
Additional warming due to zeroing of
US aerosols
Summertime temperatures increase
as much as 1.5 oC.
Only direct aerosol effect included.
white areas = insignificant differences
Mickley et al., 2012
Warming begins immediately and persists through
the decades.
A1B
D Temperature, 2050s
Daily max T
Daily mean T
Warming due to aerosol removal is strongest in
late summer / early fall
Change in surface
temperatures due to
aerosol removal,
Northeast US
Heatwaves show 1-2 K increase.
Mickley et al., 2012
D
Climate response
of Northeast to
aerosol removal
D
Daily max T
Increased diurnal
temperature range,
higher Tmax
Daily mean T
Warming, especially
in late summer, early
fall.
D
D
Sensible heat
Latent heat
Increased solar flux
in July-October
Shift from increased
latent flux to increased
sensible and LW flux in
late summer.
LW
D
D
Low cloud cover
Increased sunlight
depletes soil moisture
by late summer.
Rel humidity
Reduced cloud
cover and relative
humidity
28
Feedbacks involving soil moisture and low cloud cover
amplify local temperature response in Aug-Oct period.
D
Soil moisture depletes through
summer.
Sensible heat
Latent heat
Cloud cover diminishes in response.
Shift from increased latent flux to
increased sensible and LW flux in late
summer.
LW
Diffuse warming
Local warming
Next, we perform a more realistic set of simulations, with
changing emissions, 1950-2050.
Calculated trend in surface sulfate concentrations
Increasing sulfate from
1950-1990s.
1950
1970
1960
Decreasing sulfate
beginning in 1990s.
1980
We applied decadal trends
in anthropogenic aerosol
to the GISS climate model.
Circles show
observations.
1990
2001
Leibensperger et al., 2012a
Forcing from US anthropogenic aerosols peaks in 1980 -1990s.
Direct radiative forcing
Net DF
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.
Indirect radiative forcing from
clouds is about the same
magnitude as direct effect.
Indirect radiative forcing
Leibensperger et al., 2012a.
Cooling from U.S.
anthropogenic aerosols
during 1970-1990.
Results are from two 5-member
ensembles, with and without US
anthropogenic aerosols.
Indirect + direct effects included.
Cooling is greatest over the
Eastern US and North Atlantic.
1 oC cooling at surface over East
C
Leibensperger et al., 2012b
D Model Temperature 1970-1990
Cooling over U.S. is not co-located with
aerosol burden.
Local changes in cloud cover and soil
moisture amplify the cooling effect.
Cooling over North Atlantic strengthens
Bermuda High, increasing onshore flow of
moisture from Gulf of Mexico.
C
Results are controversial.
D Cloud Cover
%
D Soil moisture availability
%
Observations show intensification of the Bermuda High during the
1980s and early 1990s, apparently consistent with aerosol loading.
1948-1977
1978-2007
Variation of western
edge of Bermuda High
during JJA, 1948-2007.
Shift
westward
Edge = 1560-gpm contour
line at 850 hPa.
Westward extent of Bermuda High
ERA
NCEP
East
Reference
longitude
West
Period of greatest aerosol loading
1950
1980
2000
What about
effect of Pacific
Decadal
Oscillation?
Li et al., 2011
Inclusion of US anthropogenic aerosols improves match with
observed trends in surface temperatures over the East.
Eastern US
Model without US aerosols
Standard model
• Results suggest that US
anthropogenic aerosols can
explain the “warming hole.”
• Warming since 1990s can
be attributed to reductions
in aerosol sources.
Observations
Most of the warming from reducing aerosol sources
has already been realized.
Leibensperger et al., 2012b
BC
SO2
1850
1900
1950
2000
U.S. BC emissions (Tg C)
U.S. SO2 emissions (Tg S)
Timeseries of US emissions
BC deposition (g m-2 a-1)
Deposition in Adirondacks
obst
observations
Ongoing work.
BC aerosol
• warms mid- to upper troposphere
• cools surface
• stabilizes atmosphere
Sulfate cools surface, may augment
stabilization.
We will compare model BC with lake
core sediments from Adirondacks
(Husain et al., 2008) and with ice
cores from J. McConnell.
model
1860
How have competing trends
in BC and SO2 over 20th
century affected regional
climate across mid-latitudes?
1940
Leibensperger, Cusworth, and Mickley
Take home messages.
• Area burned by wildfires may increase significantly across western
North America by 2050s, depending on the ecosystem.
• Increased smoke from wildfires may thwart efforts to regulate air
quality in coming decades. This is a climate penalty.
• Decreases in aerosol loading may have unintended consequences
for regional climate, leading to warming.
Haze over Boston on May 31, 2010
Wildfires in Quebec the same day.