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AIR QUALITY AND CLIMATE
TOPICS FOR TODAY
1.
What are we worried about when we talk about “air
quality”
2.
Global air quality
3.
Background & interhemispheric transport
4.
Local/regional air quality
O2
hn
STRATOSPHERE
8-18 km
CLIMATE CHANGE AND
TROPOSPHERIC OZONE
O3
TROPOSPHERE
transport
hn
O3
NO2
NO
OH
HO2
hn, H2O
Deposition
CO, VOC
Nitrogen oxide radicals; NOx = NO + NO2
generally limiting
combustion, soils, lightning
Tropospheric
ozone
precursors
H2O2
Methane
wetlands, livestock, natural gas
Nonmethane volatile organic compounds (NMVOCs)
vegetation, combustion, industry
CO (carbon monoxide)
combustion, VOC oxidation
SENSITIVITY OF SURFACE AIR QUALITY
TO METEOROLOGICAL VARIABLES
Insights into the effect of climate change on air quality
Effect
of climate change
Ozone
PM (aerosol)
Stagnation
Temperature
?
?
?
?
Mixing depth
Precipitation
=
=
Cloud cover
Humidity
=
(relative)
[Jacob and Winner, 2008]
PREDICTIONS OF TEMPERATURE AND PRECIPITATION
CHANGES IN THE NH
Warmer everywhere, but precipitation (humidity, cloudiness, convection) trickier.
[Jacob and Winner, 2008]
EFFECT OF CLIMATE CHANGE ON OZONE AIR QUALITY
Probability of max 8-h O3 > 84 ppbv
vs. daily max. T
Ozone exceedances of 90 ppbv,
summer 2003
Lin et al. [2001]
Correlation of high ozone with temperature is driven by
(1) stagnation, (2) biogenic hydrocarbon emissions, (3) chemistry
EFFECT OF CLIMATE CHANGE ON REGIONAL STAGNATION
GISS GCM simulations for 2050 vs.
present-day climate using pollution
tracers with constant emissions
weather map illustrating
cyclonic ventilation of the eastern U.S.
2045-2052
summer
1995-2002
Pollution episodes double in duration in 2050 due to decreasing frequency of
cyclones ventilating the eastern U.S; expected result of greenhouse warming.
Mickley et al. [2004]
TOPICS FOR TODAY
1.
What are we worried about when we talk about “air
quality”
2.
Global air quality
3.
Background & interhemispheric transport
4.
Local/regional air quality
EFFECT OF 2000-2050 CLIMATE CHANGE (A1B)
ON GLOBAL TROPOSPHERIC OZONE
Tropospheric ozone in year 2000 (ppb)
2050/2000 ratio
Zonal annual mean concentrations
Ozone increases in tropical upper troposphere because of increased lightning;
but decreases in background surface air because of higher water vapor
[Wu et al., 2008b]
EFFECT OF 2000-2050 CLIMATE CHANGE (A1B)
ON GLOBAL AFTERNOON SURFACE OZONE
Ozone is predicted to increase over polluted continental regions (complex
meteorological factors + natural emission changes) and decrease over the
ocean (due to enhanced water vapour)
[Wu et al., 2008b]
CLIMATE CHANGE ALONE DEGRADES “MEAN”
AQ IN THE US
Climate change causes a 2–5 ppb positive offset over the Midwest and
northeastern United States, partly driven by decreased ventilation from
convection and frontal passages.
[Wu et al., 2008a]
…DUE TO AN INCREASE IN POLLUTION EPISODES
Maximum JJA 8-h avg ozone
99th
percentile
2050s
2000s
Midwest
Cumulative probability (%)
Max. 8-hr-avg ozone
Daily maximum temperature
(K)
Maximum JJA temperatures
2050s climate
2000s climate
40% decrease in NOx
2050s climate + DNOx
Cumulative probability (%)
Increased maximum temperatures during heat waves leads to increased ozone
Amplification of temperatures at extreme due to
• soil moisture feedbacks
• 17% decreased cyclone frequency.
[Wu et al., 2008]
TOPICS FOR TODAY
1.
What are we worried about when we talk about “air
quality”
2.
Global air quality
3.
Background & interhemispheric transport
4.
Local/regional air quality
OBSERVED TREND IN OZONE BACKGROUND OVER
CALIFORNIA IN SPRING SUGGESTS 10-15 ppbv INCREASE
OVER PAST 20 YEARS
Background: concentration that would be present in absence of local anthropogenic emissions
Trend: 0.5-0.8 ppbv yr-1
Jaffe et al. [2003]
Trend real? Driven by emission increases in Asia?
RISING OZONE BACKGROUND IN EUROPE
Hohenpeissenberg/
Payerne
polluted
3-5 km
Naja et al. [2003]
background
Changes in anthrop. NOx emissions
Mace Head, 1987-2004
[Simmonds et al., 2004]
HEMISPHERIC OZONE POLLUTION:
IMPLICATIONS OF ENHANCED OZONE BACKGROUND
FOR MEETING AIR QUALITY STANDARDS (AQS)
Europe AQS
(8-h avg.)
Europe AQS
(seasonal)
U.S. AQS
(8-h avg.)
U.S. AQS
(1-h avg.)
Was here
until 2008!
0
Preindustrial
ozone
background
20
40
60
Present-day ozone
background at
northern midlatitudes
80
100
120 ppbv
EFFECT OF INCREASING SIBERIAN FOREST FIRES ON
SUMMER SURFACE OZONE IN PACIFIC NORTHWEST
Observations
GEOS-CHEM ozone enhancements
Siberian fires
Ozone
Mean summer 2003 enhancement
of 5-9 ppbv (9-17 ppbv in events)
Jaffe et al. [2004]
SIMULTANEOUS CHANGES IN POLICY-RELEVANT
SUMMERTIME BACKGROUND OZONE
deeper PBL,
drier
soil NOx
Climate change alone would diminish the impact of background ozone, however
the background is expected to rise in the future (non-US emissions)
[Wu et al., 2008b]
CLIMATE CHANGE INCREASES SUMMERTIME OZONE
Changes in summer 8-h avg. daily maximum ozone
from 2000-2050 climate change
Higher
temperatures,
stagnation
ppb
Increased water
vapor sink
• Models agree that 2000-2050 climate change will decrease background ozone
but increase surface ozone. We find an increase of 3-5 ppb over large regions.
• Most but not all models find maximum effect during pollution episodes (up to 10
ppb) due to increased stagnation and higher temperatures.
• Most models find significant effects in Northeast/ Midwest.
• Many models disagree in Southeast partly due to different mechanisms for
oxidation of biogenic isoprene (the dominant VOC precursor)
[Wu et al., 2008a]
TOPICS FOR TODAY
1.
What are we worried about when we talk about “air
quality”
2.
Global air quality
3.
Background & interhemispheric transport
4.
Local/regional air quality
CHANGES IN AQ (SUMMER) OVER THE US (A2)
mean
95th percentile
Present Day O3
DO3 Climate only
DO3 Emissions only
Changes in O3 due to climate (driven primarily by cloud cover) are significantly
smaller than impact of emission reductions in the mean, although a larger effect
[Nolte et al., 2008]
on extremes is predicted (similar to Wu et al.).
LOOKING SPECIFICALLY IN TEXAS…
Present-Day
Future Climate
Future Climate & Land Use
84 ppb
Increases in exceedances in Houston area
[Jiang et al., 2008]
RIGHT DOWN TO THE URBAN SCALE…
Days in summer with O3 > 84 ppb (NAAQS)
50
Chicago
2000
2100
Down-scaling experiments now possible…
Summertime ozone in Chicago estimated to increase by 6-17 ppb
[Holloway et al., 2008]
EUROPEAN HEATWAVE OF 2003: A CLIMATE
CHANGE TEST CASE?
Daytime temperatures topped 38°C (over 100°F) for several days!
EMEP Stations
Substantial ozone increases were associated with
these events, although O3 did high not get as high
as in the late 1980s (due to the reduction of
precursor emissions).
Europe also experienced enhanced wildfire
activity (warmer and drier climate).
[Vautard et al., 2007]
MANAGING AIR QUALITY IN CHINA
“The key question is how
soon developing
nations will tip the
balance in favor of the
environment, so that
they can help to improve
the air quality for their
citizens and relieve global
climate change for
themselves as well as the
rest of the world. The
upgrading of the national
environmental protection
agency to the ministry
level is an indication of
China’s determination to
clean up its environment.”
[Fang et al., 2009]