EFFECT OF CLIMATE CHANGE EFFECT OF CLIMATE CHANGE ON U.S. AIR QUALITYON U.S. AIR QUALITY

Daniel J. Jacob, Harvard University

Global change inemissions

Change in U.S. air qualityChange in

climate

NOx emissions, 2020

GLOBAL CLIMATE CHANGE SINCE 1850GLOBAL CLIMATE CHANGE SINCE 1850

IPCC [2007]

IPCC PROJECTIONS OF FUTURE WARMING… IPCC PROJECTIONS OF FUTURE WARMING… AND EVALUATION OF PREVIOUS PROJECTIONSAND EVALUATION OF PREVIOUS PROJECTIONS

IPCC 1995IPCC 1990

IPCC 2007:

IPCC [2007]

Mean results from an ensemble of GCMs using the same greenhouse scenarios

PROJECTED WARMING OVER 21PROJECTED WARMING OVER 21stst CENTURY CENTURY

CO2 trend

Global temperaturetrend

CO2 = 500 ppm

The Eocene climate was warm, even at high latitudes:-palm trees flourished in Wyoming-crocodiles lived in the Arctic-Antarctica was a pine forest-deep ocean temperature was 12°C (today it is ~2°C)-sea level was at least 100 meters higher than today

EOCENE (55 to 36 million years ago): The last time EOCENE (55 to 36 million years ago): The last time in Earth history when atmospheric COin Earth history when atmospheric CO22 was above was above 500 ppm.500 ppm.

Present models cannot reproduce this warm climate – missing processes?Positive feedbacks could cause abrupt climate change but this is not well understood

OBSERVED DEPENDENCE OF AIR QUALITY ON WEATHER OBSERVED DEPENDENCE OF AIR QUALITY ON WEATHER WARNS OF POTENTIALLY LARGE EFFECT OF CLIMATE CHANGEWARNS OF POTENTIALLY LARGE EFFECT OF CLIMATE CHANGE

Interannual variability of exceedances of ozone NAAQS

# summer days with 8-hour O3 > 84 ppbv,average for 257 northeast U.S. AIRS sites

1988, hottest on record

Ozone is strongly correlated with temperature in observations (R2 ~ 0.5); reflects (1) chemistry, (2) biogenic VOC emissions, (3) association with stagnation

Lin et al. [2001]

USE OZONE-TEMPERATURE CORRELATION TO ESTIMATE USE OZONE-TEMPERATURE CORRELATION TO ESTIMATE EFFECT OF CLIMATE CHANGE ON AIR QUALITYEFFECT OF CLIMATE CHANGE ON AIR QUALITY

Probability of max 8-h O3 > 84 ppbvvs. daily max. temperature

-4

-2

0

2

4

6

8

10

1900 1950 2000 2050 2100

Sum

mer

Tem

pera

ture

Ano

mal

y (o

C)

CCSM 1 PCM 1CCSM 2 PCM 2CCSM 3 PCM 3CCSM 4 HadCM3ECHAM 1 GFDL 0ECHAM 2 GFDL 1ECHAM 3 GISS

Projected T change for northeast U.S. in 2000-2100 simulated with ensemble of GCMs for different scenarios [IPCC, 2007]

T = 3K

Pro

bab

ilit

y

Temperature, K

Probabilityof exceedancedoubles

By 2025, T = 1-3 K depending on model and scenario; use statistical approach at right to infer increased probability of ozone exceedance for a given region or city assume nothing else changes. Effect is large!

Loretta Mickley (Harvard) and Cynthia Lin (UC Davis)

Lin et al. [2001]

NortheastLos AngelesSoutheast

STATISTICAL METHOD TO PROJECT NAAQS EXCEEDANCESSTATISTICAL METHOD TO PROJECT NAAQS EXCEEDANCESFOR A GIVEN LOCATION OR REGION IN A FUTURE CLIMATEFOR A GIVEN LOCATION OR REGION IN A FUTURE CLIMATE

Apply ensemble of GCMs to simulate future climate

Apply subgrid variability to T from present-day climatology

Apply local or regional probability of NAAQS exceedance = f(T)

Obtain probability of NAAQS exceedance in future climate assuming constant emissions

Obtain daily max T for individual grid squares

Obtain daily max T for individual locations

APPLICATION TO PROJECT FUTURE EXCEEDANCES OF OZONE NAAQSAPPLICATION TO PROJECT FUTURE EXCEEDANCES OF OZONE NAAQSIN THE NORTHEAST UNITED STATESIN THE NORTHEAST UNITED STATES

Statistical method allows quick local assessment of the effect of climate change, but it has limitations:

• gives no insight into the coupled effect of changing emissions• some fraction of variance unresolved by statistical model• no good statistical relationships for PM developed so far

Loretta Mickley (Harvard) and Cynthia Lin (UC Davis)

Three IPCC(2007) GCMs,downscaled to capturelocal variability

Northeast U.S.

2010 2032 2055 2078 2100YEAR

Nu

mb

er o

f ex

ceed

ance

day

s

30

20

10

0

Average for the 257 AIRS sites of Lin et al. [2001]

EFFECT ON CLIMATE CHANGE ON BOUNDARY LAYER DEPTH EFFECT ON CLIMATE CHANGE ON BOUNDARY LAYER DEPTH

Projected A1 2000-2050 changes in surface T and mixing depth, GISS GCM 3

Change in surface temperature (K) Change in afternoon mixing depth (ratio)

Loretta J. Mickley and Shiliang Wu, Harvard

Response of boundary layer mixing to climate change is largely driven by local soil moisture; drying of Texas due to NE shift of Bermuda High

EFFECT OF CLIMATE CHANGE ON REGIONAL STAGNATIONEFFECT OF CLIMATE CHANGE ON REGIONAL STAGNATION

Pollution episodes double in duration in 2050 climate due to decreasing frequency of cyclones ventilating the eastern U.S; this decrease is an expected consequence of greenhouse warming.

GISS GCM 2’ simulations for 2050 vs. present-day climate using pollution tracers with constant emissions

Mickley et al. [2004]

2045-2052

1995-2002

summer

Mid-latitudes cyclones tracking across southern Canada are the main drivers of northern U.S. ventilation

Northeast U.S.CO pollution tracer

Clean airsweepsbehind cold front

Sunday night’s weather map

CLIMATOLOGICAL DATA CONFIRM DECREASE IN FREQUENCY CLIMATOLOGICAL DATA CONFIRM DECREASE IN FREQUENCY OF MID-LATITUDE CYCLONES OVER PAST 50 YEARSOF MID-LATITUDE CYCLONES OVER PAST 50 YEARS

Annual number of surface cyclones and anticylones over North America

Cyclone frequency at 30o-60oN

cyclones

anticyclones

1000

100

500

1950 1980

Agee [1991]

McCabe et al. [2001]

COMPREHENSIVE APPROACH FOR INVESTIGATING COMPREHENSIVE APPROACH FOR INVESTIGATING EFFECT OF CLIMATE CHANGE ON AIR QUALITYEFFECT OF CLIMATE CHANGE ON AIR QUALITY

Global climate model (GCM)

Global chemical transport model

(CTM)for ozone-PM

Regional climate model (RCM)

Regional CTM for ozone-PM

boundaryconditions

inputmeteorology

inputmeteorology

boundaryconditions

IPCCfuture emission

scenario

greenhousegases

ozone-PM precursors

Need to run many years to obtain sufficient statistics expensive!

internal EPA project (CIRAQ) and several STAR projects

GLOBAL CHANGE AND AIR POLLUTION (GCAP)GLOBAL CHANGE AND AIR POLLUTION (GCAP)

GISS GCM

GEOS-Chemglobal CTM

MM-5 RCM

CMAQregional CTM

boundaryconditions

inputmeteorology

inputmeteorology

boundaryconditions

IPCC emissionscenario

greenhousegases

ozone-PM precursors

Applied to 2000-2050 global change simulations with IPCC SRES A1 scenario

EPA-STAR project : D.J. Jacob and L.J. Mickley (Harvard), J.H. Seinfeld (Caltech), D. Rind (NASA/GISS), D.G. Streets (ANL), J. Fu (U. Tenn.) , D. Byun (U. Houston)

2000-2050 EMISSIONS OF OZONE PRECURSORS (A1)2000-2050 EMISSIONS OF OZONE PRECURSORS (A1)

Global United States

2000 emissions

% change,

2000-2050

2000 emissions % change,

2000-2050

NOx, Tg N y-1

Anthropogenic

Lightning

Soils (natural)

34

4.9

6.1

+71%

+18%

+8%

6.0

0.14

0.35

-39%

+21%

+11%

NMVOCs, Tg C y-1

Anthropogenic

Biogenic

46

610

+150%

+23%

9.3

40

-52%

+23%

CO, Tg y-1 1020 +25% 87 -47%

Methane, ppbv 1750 2400 (+37%)

Shiliang Wu, Harvard

• Global increase in anthropogenic emissions but 40-50% decreases in U.S.!• Climate-driven increases in natural NOx, NMVOC emissions

CHANGES IN SUMMER MEAN 8-h AVG. DAILY MAXMUM OZONE CHANGES IN SUMMER MEAN 8-h AVG. DAILY MAXMUM OZONE FROM 2000-2050 CHANGES IN CLIMATE AND GLOBAL EMISSIONS FROM 2000-2050 CHANGES IN CLIMATE AND GLOBAL EMISSIONS

2050 emissions & 2000 climate) 2050 emissions & climate)

2000 conditions ( ppb) 2000 emissions & 2050 climate)

Shiliang Wu, Harvard

SENSITIVITY OF POLLUTION EPISODES TO GLOBAL CHANGESENSITIVITY OF POLLUTION EPISODES TO GLOBAL CHANGE

• In northeast and midwest, climate change effect reaches 10 ppbv for high-O3 events; longer and more frequent stagnation episodes• near-zero effect of climate change in southeast

Shiliang Wu, Harvard

Midwest

Southeast

NortheastMidwest

Southeast

NortheastMidwest

Southeast

Northeast

Cumulative probability (%)

Ma

x-8

h-a

vg

ozo

ne Present

Future climateFuture emissionsFuture climate & emis

Midwest

Cumulative probability (%)Cumulative probability (%)Cumulative probability (%)

Ma

x-8

h-a

vg

ozo

ne Present

Future climateFuture emissionsFuture climate & emis

Midwest

Cumulative probability (%)

Max-8h-

avg

ozo

ne

Northeast

Cumulative probability (%)

Max-8h-

avg

ozo

ne

Cumulative probability (%)

Max-8h-

avg

ozo

ne

Northeast

Cumulative probability (%)

Southeast

Ma

x-8

h-a

vg

ozo

ne

Cumulative probability (%)Cumulative probability (%)

Southeast

Ma

x-8

h-a

vg

ozo

ne

Summer probability distribution of daily 8-h max ozone

median90th

99th

CLIMATE CHANGE PENALTY CLIMATE CHANGE PENALTY AS ADDED REQUIREMENTS ON EMISSION REDUCTIONSAS ADDED REQUIREMENTS ON EMISSION REDUCTIONS

2000-2050 climate change means that we will need to reduce NOx emissions by 50% instead of 40% to achieve the same ozone air quality goals in the northeast

Shiliang Wu, Harvard

2000 climate- 40% U.S.NOx

emissions

2050 climate-50% NOx

emissions

2050 climate-60% NOx

emissions

OZONE CLIMATE CHANGE PENALTY WILL BE HIGHER OZONE CLIMATE CHANGE PENALTY WILL BE HIGHER IF WE DON’T REDUCE EMISSIONSIF WE DON’T REDUCE EMISSIONS

Change in mean 8-h daily max ozone (ppb) from 2000-2050 climate change

with 2000 emissions with 2050 emissions

Reducing U.S. anthropogenic emissions significantly mitigates the climate change penalty

Shiliang Wu, Harvard

EFFECT OF 2000-2050 CLIMATE CHANGE EFFECT OF 2000-2050 CLIMATE CHANGE ON POLICY-RELEVANT BACKGROUND (PRB) OZONEON POLICY-RELEVANT BACKGROUND (PRB) OZONE

2000 conditions: PRB ozone, ppb 2000 emissions & 2050 climate)

(2050 emissions & 2000 climate) (2050 emissions & climate)

2050 climate decreases PRB in subsiding regions, increases in upwelling regions2050 emissions increase PRB due to rising methane, Asian emissions

Shiliang Wu,Harvard

2000-2050 EMISSIONS OF PM2000-2050 EMISSIONS OF PM2.52.5 PRECURSORS (A1) PRECURSORS (A1)

Global United States

2000 emissions

% change,

2000-2050

2000 emissions % change,

2000-2050

SOx, Tg S y-1

Anthropogenic

Natural

59

21

+ 38%

0%

9

-

- 80%

NOx, Tg N y-1

Combustion

Lightning

Soils (natural)

34

4.9

6.1

+ 71%

+ 18%

+ 8%

6.0

0.14

0.35

- 39%

+21%

+11%

NH3, Tg N y-1

Anthropogenic

Natural

40

17

+ 43%

+ 0%

2.2

0.8

+ 40%

+ 0%

BC, Tg C y-1 7.9 - 27% 0.6 - 56%

OC, Tg C y-1

Combustion

Biogenic (SOA)

33 - 17% 1.5 - 34%

David Streets, ANL and Shiliang Wu, Harvard

EFFECT OF 2000-2050 GLOBAL CHANGE ON ANNUAL MEAN EFFECT OF 2000-2050 GLOBAL CHANGE ON ANNUAL MEAN SULFATE CONCENTRATIONS (SULFATE CONCENTRATIONS (g mg m-3-3))

2000 conditions: sulfate, g m-3 2000 emissions & 2050 climate)

(2050 emissions & 2000 climate) 2050 emissions & 2050 climate)

Shiliang Wu, Harvard

Climate change increases sulfate by up to 0.5 g m-3 in midwest (more stagnation), decreases sulfate in southeast (more precipitation)

EFFECT OF 2000-2050 GLOBAL CHANGE ON ANNUAL MEAN EFFECT OF 2000-2050 GLOBAL CHANGE ON ANNUAL MEAN ORGANIC CARBON (OC) AEROSOL CONCENTRATIONS (ORGANIC CARBON (OC) AEROSOL CONCENTRATIONS (g mg m-3-3))

Shiliang Wu, Harvard

Climate change effect is mainly through biogenic SOA and is smallbecause of compensating factors (higher biogenic VOCs, higher volatility)

2000 conditions: OC, g m-3 2000 emissions & 2050 climate)

(2050 emissions & 2000 climate) 2050 emissions & 2050 climate)

EFFECT OF 2000-2050 GLOBAL CHANGE ON ANNUAL EFFECT OF 2000-2050 GLOBAL CHANGE ON ANNUAL MEAN PMMEAN PM2.52.5 CONCENTRATIONS ( CONCENTRATIONS (g mg m-3-3))

Shiliang Wu, Harvard

2000 conditions: PM2.5, g m-3 2000 emissions & 2050 climate)

(2050 emissions & 2000 climate) 2050 emissions & 2050 climate)

Effect of climate change is small (at most 0.3 g m-3) – but this doesn’t accountfor change in wildfires…

WILDFIRES: A SIGNIFICANT PMWILDFIRES: A SIGNIFICANT PM2.52.5 SOURCE SOURCE

S. California fire plumes,Oct. 25 2004

Total carbonaceous (TC) aerosol averaged over all contiguous U.S. IMPROVE sites

~100 IMPROVE sites nationwide

• Interannual variability in annual mean carbonaceous PM2.5. is largely determined by wildfires• Open fires contribute about 25% of annual mean PM2.5 in the western U.S., 10% in the east • Dominant contributions from western U.S. fires (in the west), Canadian fires (in the northeast), prescribed fires (in the southeast) Park et al. [2007]

INCREASING WILDFIRE FREQUENCY IN PAST DECADESINCREASING WILDFIRE FREQUENCY IN PAST DECADES

Westerling et al. [2006]

Canadian fires [Gillet et al., 2004]

1920 1940 1960 1980 2000

Temperature and drought indexcan explain 50-60% of interannual variability in fires

Dominick Spracklen, Harvard

EFFECT OF 2000-2050 CLIMATE CHANGE EFFECT OF 2000-2050 CLIMATE CHANGE ON WESTERN U.S. WILDFIRES ON WESTERN U.S. WILDFIRES

GISS GCM, IPCC A1 scenario, using fire frequency regression on T and drought

observed

Mean biomass burned per year is projected to increase by 50% in 2050, resulting in 10% increase in annual mean PM2.5

Dominick Spracklen, Harvard

CONCLUSIONSCONCLUSIONS

• Climate change over the next decades is likely to have a negative effect on ozone and PM U.S. air quality– effect is most pronounced during pollution episodes– probability of ozone NAAQS exceedances might double in some regions

by 2025 if emissions stay constant• Climate change for 2000-2050 is projected to increase mean summertime

ozone by 1-5 ppb (mean 8-h daily max) and up to 10 ppb (pollution episodes) – effect is largest in central and northeast, much weaker in southeast– Model results suggest that this will require an additional 10% decrease in

NOx emissions to meet ozone air quality goals in the northeast – the ‘climate change penalty’.

• Policy-relevant background (PRB) ozone is expected to increase by 1-5 ppb by 2050 (highest in the west) due to rising methane and non-U.S. emissions– climate change partly offsets this effect

• Effect of climate change on PM2.5 air quality may be relatively small because of canceling factors– but climate-driven increases in wildfires may be an important issue