Transcript Attaining the new US ozone NAAQS

A regional-to-global perspective on
attaining the new U.S. ozone NAAQS
Arlene M. Fiore
Acknowledgments:
George Milly, Lukas Valin (LDEO)
Harald Rieder (U Graz, Austria)
Lok Lamsal (NASA GSFC)
83520601
Panel on Meeting the New Ozone Standard
Energy Summit 2015
University of Wisconsin, Madison, WI
October 13, 2015
Ground-level O3 is produced photochemically in the
atmosphere, from both natural and anthropogenic sources
Raises background
ozone levels
CH4
+
NOx
O3
NMVOC
Fuel local-to-regional ozone
pollution episodes
Observed surface ozone includes background plus any
ozone produced from local-to-regional emissions
U.S. ozone abatement strategies evolve with
our understanding of the O3 problem
O3 smog recognized
as an URBAN problem:
Los Angeles,
Haagen-Smit identifies
chemical mechanism
1950s
Abatement Strategy:
NMVOCs
Smog considered
REGIONAL problem;
role of biogenic
VOCs discovered
A GLOBAL
perspective:
role of intercontinental
transport, background
Present
1980s
+ NOx
+ CH4??
Lower O3 NAAQS level likely expands non-attainment regions
2011-2013 ozone design values at EPA approved ozone monitoring sites
Cooper et al., Science, 2015
Cleaner U.S. air is visible from space
Satellite (OMI) tropospheric NO2 columns
c/o Lok Lamsal & Bryan Duncan, NASA GSFC
New OMI NO2 website: airquality.gsfc.nasa.gov
Tropospheric column NO2 higher on weekdays vs. weekends,
mainly attributable to weekly cycle in diesel NOx emissions
WEEKDAY
WEEKEND
Mid-2000s
Early 2010s
Luke Valin
LDEO,
in prep.
Following NOx emission controls, current weekday
tropospheric NO2 columns look more like past weekends
Similar patterns occur in surface ozone
90th% summer afternoon surface ozone (U.S. EPA AQS)
WEEKDAY
WEEKEND
Mid2000s
Early
2010s
Luke Valin
LDEO,
in prep.
 Additional diesel NOx controls would lower weekday
surface ozone (and tropospheric NO2 columns)
 Implies regional NOx-sensitive ozone production
Future projections in the context of the revised O3 NAAQS
Number of summer (JJA) days with MDA8 O3 > 70 ppb at CASTNet sites
APPROACH
1. Use chemistry-climate model (GFDL CM3) to estimate regional-scale changes
2. Apply modeled changes at each percentile to observed distribution at each site
OBSERVED OBSERVED + MODELED
2021-2025
2001-2005
(RCP8.5)
# DAYS
?
40% decrease in EUS NOx emissions over near-term (2020-2005)
leads to 3 or fewer summer days with MDA8 O3 > 70 ppb
at all but 5 sites
Rieder et al., in prep, 2015
Future projections in the context of the revised O3 NAAQS:
a monitoring site
in Dodge County, WI
2001-2005
OBSERVED
2021-2025
OBSERVED + MODEL
(RCP8.5) REGIONAL
CHANGES AT EACH
PERCENTILE
 Moving from 75 to 70 ppb doubles # days > NAAQS level
 Projected regional-scale O3 decreases suggest near-term
attainment of new standard possible
H. Rieder
The “tightening vise” of ozone management
Ozone concentration
Standard
Local
Regional
Hemispheric
background
Historical
Future
Future
(alternate view)
Keating, T. J., J. J. West, and A. Farrell (2004) Prospects for international management of intercontinental air pollutant transport, in A. Stohl,
Ed., Intercontinental Transport of Air Pollution, Springer, p. 295-320.
 Future may require concerted efforts to lower background
Reducing methane lowers hemispheric background ozone
(plus climate co-benefit)
Benefits of ~25% decrease in global anthropogenic methane emissions
OZONE AIR QUALITY
CLIMATE
Global mean
avoided warming in
2050 (°C)
Range over
18 models
North
America
Europe
[WMO/UNEP, 2011]
East
Asia
South
Asia
 ~ 1 ppb across the northern hemisphere
[Fiore et al., JGR, 2009; TF HTAP, 2007, 2010; Wild et al., ACP, 2012]
 7700-400,000 annual avoided cardiopulmonary
premature mortalities in the N. Hemisphere
uncertainty in concentration-response relationship only
[Casper Anenberg et al., ES&T, 2009]
Background over the U.S.A. is highest in the west
(at altitude) and in spring
Estimated in a model (GEOS-Chem) by turning off N. American
anthropogenic emissions
Summer 1995 afternoon average background ozone
Ozone (ppb)
Monthly afternoon mean ozone
over the Northeast U.S.A., 2001
OBS. Model Background
J F M A M J J A S O N D
Month of 2001
[Fiore et al., JGR, 2003]
12
[Fiore et al., JGR, 2002]
20
Ozone (ppb)
28
37
Latest background estimates (recent years, higher resolution) support
general conclusions; emphasis now on episodic background events
e.g., Wu et al., 2008; Wang et al., 2009; McDonald-Bueller et al. 2011; Mueller & Mallard, 2011; Zhang
et al., 2011; 2014; Emery et al., 2012; Lin et al., 2012ab; Fiore et al., AtmEnv, 2014
Setting achievable standards requires
accurate knowledge of background levels
typical average
background
U.S. “background” events over WUS
(model estimates) [e.g., Lin et al., 2012ab] U.S. National Ambient Air Quality Standard
[Fiore et al., 2003;
for O3 has evolved over time
Wang et al., 2009;
Zhang et al., 2011]
2015
8-hr
20
120 ppb
70 ppb 75 ppb 84 ppb
40
60
2008
8-hr
80
1979
1-hr avg
1997
8-hr
100
O3 (ppbv)
120
Adapted from D.J. Jacob & NAS, 2009
“Allowable” O3 produced from U.S. anthrop. sources (“cushion”)
Lowering U.S. O3 NAAQS levels implies thinning cushion between
regionally produced O3 and background
An Air Quality Management Challenge: NATURAL EVENTS
How to detect and attribute accurately?
WILDFIRES
Examples of how
satellite, in situ
measurements
and models can be
combined to
detect and attribute
exceptional events
Fiore et al., EM 2014
(NASA AQAST special issue)
STRATOSPHERIC
INTRUSIONS
An Air Quality Management Challenge: CLIMATE CHANGE
Will warmer temperatures worsen O3 pollution?
Observations at U.S. EPA CASTNet site Penn State, PA 41N, 78W, 378m
July mean MDA8 O3 and July mean daily maximum temperature
G. Milly
Figure 6a of Fiore, Naik, Leibensperger, JAWMA, 2015
 Downward ozone trend as EUS NOx emission controls are implemented
 Decreasing NOx emissions reduces sensitivity of O3 to temperature;
continued controls should guard against climate-driven increases [e.g.,
Bloomer et al., 2009; Rasmussen et al., 2012; Brown-Steiner et al., 2015]
Attaining the new U.S. ozone NAAQS:
A regional-to-global perspective
• Continued regional NOx decreases should facilitate attainment
with new standard (NOx-sensitive ozone production) over the
eastern U.S.A.
• Background contributions to U.S. surface ozone vary in space
and time
• Exceptional events may become more common with respect to
a tighter standard and under climate change (e.g., wildfires)
• Trans-boundary transport could increase if foreign emissions
rise (see next panel)
• Methane emission reductions would lower hemispheric
background ozone levels (and also decrease climate forcing)