INTERACTIONS OF AIR POLLUTION AND CLIMATE CHANGE Daniel J. Jacob How do air pollutants contribute to climate change? How will climate change affect air.

INTERACTIONS OF AIR POLLUTION AND CLIMATE CHANGEINTERACTIONS OF AIR POLLUTION AND CLIMATE CHANGE

Daniel J. Jacob

• How do air pollutants contribute to climate change?• How will climate change affect air quality?

with funding from NASA, EPA, NSF, EPRI, NOAA

MILLENIAL NORTHERN HEMISPHERE TEMPERATURE TRENDMILLENIAL NORTHERN HEMISPHERE TEMPERATURE TREND [IPCC, 2001; after Mann, 1999][IPCC, 2001; after Mann, 1999]

Global mean surface air temperature To has increased by 0.6 ± 0.2 K over the past century; ocean temperatures, sea level, cloudiness, precipitation also have increased.

Gray shading: two standard errors

RADIATIVE FORCING OF CLIMATE CHANGERADIATIVE FORCING OF CLIMATE CHANGE

Incomingsolar

radiation

Reflected solar radiation (surface, air, aerosols, clouds)

Fout

Fin

IR terrestrial radiation ~ T4; absorbed/reemitted by greenhouse gases, clouds, absorbing aerosols

EARTH SURFACE

• Stable climate is defined by radiative equilibrium: Fin = Fout

• Instantaneous perturbation Radiative forcing F = Fin – Fout; • Greenhouse gases F > 0 (warming)• Absorbing aerosols F > 0 (warming) • Scattering aerosols F < 0 (cooling)

General circulation models (GCMs) give = To F = 0.3-1.4 K m2 W-1; is relatively insensitive to nature of forcing

GLOBAL RADIATIVE FORCING OF CLIMATE, GLOBAL RADIATIVE FORCING OF CLIMATE, 1750-present [IPCC, 2001] 1750-present [IPCC, 2001]

AIR QUALITY RELATED

AQ-related greenhouse forcing: 0.48 (CH4) + 0.35 (O3) + 0.2 (BC) = 1.03 W m-2

…compare to 1.46 W m-2 for radiative forcing by CO2

Also note –0.50 W m-2 forcing from sulfate and OC aerosols; SO2 emission reductions result in positive radiative forcing

HANSEN BEST ESTIMATES OF GLOBAL RADIATIVE FORCINGS HANSEN BEST ESTIMATES OF GLOBAL RADIATIVE FORCINGS …including indirect effects [Hansen and Sato, PNAS 2001]…including indirect effects [Hansen and Sato, PNAS 2001]

AQ-related greenhouse forcing: 0.7 (CH4) + 0.5 (O3) + 0.8 (BC) = 2.0 W m-2

…larger than CO2 !

Cooling from reflective anthropogenic aerosols: -1.3 (dir.) – 1.0 (indir.) = -2.3 W m-2 …very large!

TROPOSPHERIC OZONE FORCING COULD BE LARGER TROPOSPHERIC OZONE FORCING COULD BE LARGER THAN CURRENT ESTIMATESTHAN CURRENT ESTIMATES

Standard model:

F = 0.44 W m-2

“Adjusted” model

(lightning and soil NOx decreased,

biogenic hydrocarbons increased):

F = 0.80 W m-2

[Mickley et al., JGR 2001]

Global simulation of late 19th century ozone observations in France with the GISS GCM

… because of uncertainty on preindustrial ozone (models overestimate 19th century observations)3 km altitude

REGIONAL CLIMATE RESPONSE FROM INHOMOGENEOUS REGIONAL CLIMATE RESPONSE FROM INHOMOGENEOUS RADIATIVE FORCING BY AEROSOLS AND OZONERADIATIVE FORCING BY AEROSOLS AND OZONE

Assessing the regional climate response to such regional forcings is a very difficult problem; requires observation-based analyses, GCM studies

Aerosol radiative forcing over Indian subcontinent during winter monsoon

CLIMATE RESPONSE FROM TROPOSPHERIC OZONECLIMATE RESPONSE FROM TROPOSPHERIC OZONE Jun-Aug surface warming (K) in GISS GCM Jun-Aug surface warming (K) in GISS GCM

when tropospheric ozone increases from preindustrial to presentwhen tropospheric ozone increases from preindustrial to present

Difference

Tropospheric ozone (0.46 W m-2) Equivalent CO2 (0.46 W m-2)

(white = insignificant or high altitude)

Complicated patterns! Largest warmings tend to be downwind of ozone source regions

Mickley et al., JGR 2003

DOUBLE DIVIDEND OF METHANE EMISSION CONTROLSDOUBLE DIVIDEND OF METHANE EMISSION CONTROLSFOR AIR QUALITY AND CLIMATEFOR AIR QUALITY AND CLIMATE

50%

NM

VO

C

1995

(bas

e)

50%

CH 4

50%

NO

x20

30 A

120

30 B

1

50%

NM

VO

C50

% C

H 4

50%

NO

x20

30 A

120

30 B

1

IPCC scenario 2030 vs. 2000

Fossil fuel NOx emissions

Global U.S.

Methane concentration

A1 (pessimistic) +80% -30% +35%

B1 (optimistic) +10% -60% +20%

# pollution events (O3 > 80 ppb)

Sensitivity simulations with GEOS-CHEM global CTM [Fiore et al., GRL 2002]

EFFECT OF CLIMATE CHANGE ON AIR QUALITYEFFECT OF CLIMATE CHANGE ON AIR QUALITY

• Effect of climate change on air pollution meteorology has so far received no attention in GCMs

• Well-documented O3 vs. T relationship warns that effect could be large!

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

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

Lin et al. [Atm. Env. 2001] analysis of 1980-1998 AIRS data

1988, hottest on record!

EFFECT OF FUTURE CLIMATE CHANGE ON U.S. AIR QUALITY:EFFECT OF FUTURE CLIMATE CHANGE ON U.S. AIR QUALITY:WHAT CAN WE EXPECT?WHAT CAN WE EXPECT?

Temperature

Precipitation

Cloudiness

Relative humidity ?

Wind speed ?

Mixing depths??

Frontal passages,circulation??

Ozone PM

++ +

?- -

likely increase unclear

EFFECT OF CLIMATE CHANGE ON POLLUTANT VENTILATIONEFFECT OF CLIMATE CHANGE ON POLLUTANT VENTILATION

GISS GCM simulation of CO and black carbon for 1990-2050 transient climateIPCC A1 scenario, To = 2 K from 1990 to 2050

1995-1999 2045-2049

More frequent pollution episodes in eastern U.S. in 2050 climate; opposite in western U.S. What are the driving meteorological factors? We are investigating.

L.J. Mickley, work in progress

Summertime frequency distributions of 24-h average CO and BC over northeast U.S.

CLIMATE CHANGE AND INTERCONTINENTAL CLIMATE CHANGE AND INTERCONTINENTAL TRANSPORT OF POLLUTIONTRANSPORT OF POLLUTION

Surface ozone and sulfate enhancements from present-day Asian anthropogenic emissions

GEOS-CHEM simulations for 1997, 2001

What will be the combined effects of rising Asian emissions and climate change?

ozone[Li et al., JGR 2002]

sulfatePark et al., in prep.]

EPA STAR PROGRAMEPA STAR PROGRAMAssessing the Consequences of Global Change for Air Quality:

Sensitivity of U.S. air quality to climate change and future global impacts

Six 3-year projects funded in 2003, including GCM studies and model sensitivity analyses

GCIAQ project: Harvard (Jacob), Caltech (Seinfeld), NASA/GISS (Rind), DOE/ANL (Streets), U. Tennessee (Fu), EPA/ORD (Gilliland), EPA/OAQPS (Jang)

GISS GCM1950-2050 transient climate

simulation

GEOS-CHEM CTMglobal O3-PM

simulation

MM5 mesoscaledynamics simulation

CMAQregional O3-PM

simulation

Archiveresults

boundaryconditions

met. input

met. input

boundaryconditions

Compare 2000 and 2050 climates

2050 vs. 1990 climate

SOME RESEARCH NEEDS FALLING THROUGH THE CRACKSSOME RESEARCH NEEDS FALLING THROUGH THE CRACKS

• Climate response to regional radiative forcing by aerosols and ozone

– Need GCM, observational studies

• Radiative properties of U.S. aerosols

– Need to combine satellite measurements of aerosol optical depth (MODIS, MISR) with in situ observations, models

MODIS optical depths (Aug. 2001)

• Analysis of observed ozone and PM relationships with meteorological variables in present-day climate

-- Need to test model simulations of these relationships and develop observation-based diagnostics for predicting effects of climate change

• Effect of climate change on mercury, POPs -- Need multimedia global models to describe changes in partitioning between reservoirs, atmospheric transport