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Air Quality and Climate Change
Weather has a large effect on U.S. air quality.
Loretta Mickley
Harvard University
What U.S. city is this?
Co-authors:
Amos Tai, Eric Leibensperger, and
Xu Yue, Daniel Jacob, Jennifer Logan
U.S. Air Quality Smog Blog, alg.umbc.edu/usaq
Weather has a large effect on U.S. air quality.
Jan 23, 2013
warmer
cooler
Salt Lake City
Persistent temperature inversions this January over Northern Utah
led to unhealthy air 11 out of 31 days.
Airnow; NASA Earth Observatory
2
Both emissions and weather have been changing over the
United States.
OMI NO2 data
Thanks to Bryan Duncan
3
Temperatures have been increasing rapidly since the 1980s.
Temperature anomaly (o C)
Contiguous US
1
0
Warming trend
after 1980
-1
1880
2000
What do these trends mean for surface air quality?
NASA GISS temperature analysis, GISTEMP
4
www.epa.gov/airdata/ad_viz_ozcompare.html
Number of ozone exceedances in Chicago and St. Louis
looked promisingly low in recent years.
Chicago
Number of days MDA8
ozone > 75 ppb
St. Louis
Airnow
5
www.epa.gov/airdata/ad_viz_ozcompare.html
Drought + heat wave in 2012 ramped up number of ozone
exceedances.
Chicago
Number of days MDA8
ozone > 75 ppb
St. Louis
Airnow
6
We know that surface ozone is sensitive to stagnation.
Stagnant air covers East.
Clear skies.
High temperatures.
Cold front moves through.
Cool, clean air.
Leibensperger et al., 2010
7
Cold fronts clear away pollution in central and eastern United
States.
High ozone levels
Clean air
Leibensperger et al., 2010
8
Cyclones passing through Great Lakes/ Southern Canada
region are associated with cold fronts .
Cyclone
Stagnant air.
Cold front moves through.
Leibensperger et al., 2010
9
Number of cyclones over
Great Lakes region
Climate models predict decreasing trend in number of Great
Lakes cyclones in warming atmosphere.
Turner et al., 2013
30%RCP
decrease
8.5
Climate model projection
of JJA cyclone number over
Great Lakes region.
10
Climate models predict more persistent weather in future
atmosphere over mid-latitudes.
What are the implications for air quality?
As high latitudes warm, slower
eastward progression of Rossby
waves in the upper-level flow.
Francis et al., 2012
11
Climate penalty for ozone air quality:
Increased stagnation + high temperatures will likely increase
surface ozone.
D MDA8 JJA ozone
4
2
2000-2050 change in JJA MDA8
ozone due to climate change.
0
-2
-4
6 ppb
ppb
4
4
2
2
0
0
-2
-2
-4
-4
Climate generated by NASA GISS Model 3; Tai et al., 2013
12
Response of PM2.5 to changing meteorology is more
complicated.
Observed sulfate correlates with temperature, but . . . .
nitrate anti-correlates
with temperature.
Observed relationships with Temperature (% K-1)
Tai et al., 2010
13
Net effect of 2000-2050 climate change on PM2.5 is small,
at least when considering circulation changes.
D annual mean PM2.5
2000-2050 change in annual
mean PM2.5 due to changing
circulation.
Increased
maritime flow
Increased stagnation
Changes are small, on the order of 0.5 mg m-3.
Tai et al., 2012
14
Wildfires may become the dominant player in
changing PM2.5 in future atmosphere.
Modeled 2050s response of surface PM2.5
to trends in circulation and in wildfires.
Tai et al., 2012; Yue et al., 2013
15
Doubling of wildfire activity in warmer and drier 2050s
significantly increases PM2.5 in the western U.S.
D organic PM2.5
2000-2050 change in JJA mean
organic carbon particles due to
changing wildfires.
NASA GISS Model 3; Yue et al., 2013
16
Increase in organic PM2.5 in 2050s is especially large
during extreme wildfire events.
Cumulative probability of daily mean
concentrations of organic particles
2050s
doubling
Presentday
Projection shows doubling of
organic particles during fire events
over Rocky Mountains in MayOctober timeframe for the 2050s.
NASA GISS Model 3; Yue et al., 2013
17
Take home message 1
The response of air quality to climate change depends on trends
in extreme events: stagnation, inversions, or wildfires.
Persistent temperature
inversions this January over
Northern Utah led to unhealthy
air 11 out of 31 days.
warmer
cooler
Salt Lake City
Airnow; NASA Earth Observatory
18
Take home message 2:
The climate penalty for ozone air quality could be large.
D MDA8 JJA ozone
4
2
2000-2050 change in MDA8 JJA
ozone due to climate change.
0
-2
-4
ppb
4
4
2
2
0
0
-2
-2
-4
-4
NASA GISS Model 3; Tai et al., 2013
19
Take home message 3:
Air quality in the West is vulnerable to changing wildfire in a
warmer, drier climate.
Cumulative probability of daily mean
concentrations of organic particles
2050s
doubling
Presentday
Projection shows doubling
of organic particles during
wildfires over Rocky
Mountains in 2050s.
NASA GISS Model 3; Yue et al., 2013
20