Air Quality in a Changing Climate

Allen L. RobinsonCarnegie Mellon University

Funding: US EPA

Presented at 2018 BC Lung Association Air Quality and Health Workshop: “The Future of Air Quality Management for Improved Public Health” Vancouver, Canada February 5, 2018.

Many linkages between air quality and climate

Climate Change

Air Pollution Meteorology

“Natural” Emissions

Anthropogenic Emissions

Air Pollution Concentrations

Replace with better ima

Climate Change and Air Pollution Meteorology

• Not just temperature• Spatial heterogeneity• Models don’t always agree

on details (esp. spatial patterns)

(Val Martin et al. ACP 2015)RCP = Representation Concentration PathwayRCP4.5 is an intermediate scenario

Decrease

No Change

IncreaseTemperature

Precipitation

BL Height

O3“Climate Penalty” – almost all studies predict an increase

Met Factors & O3:• Temperature ⇑⇑• Absolute humidity ⇓• Mixing / dilution

• Wind speed ⇓• Mixing height ⇓

• Clouds ⇓• Precipitation ⇑

Δ MDA8 O3 (ppb)

Effect of a ∆T of 2.5 on July MDA8 O3 using constant 2001 emissions. (Dawson et al. AE 2006)

Climate penalty = increase in pollution from climate change assuming constant emissions

PM2.5 “Climate Penalty” – more variability among studies

Δ PM2.5

(μg m-3)

(Dawson et al. JGR 2009)

• Summer increase mainly oxidant driven.• Winter decrease mainly driven by increasing T and nitrate partitioning.

• Increase over Northeast due to decreased precipitation.

January (-0.6 μg m-3) July (+2.2 μg m-3)

Biogenic emissions depend strongly on Climate

(Baghi et al. Biogeo Disc 2012https://cfpub.epa.gov/roe/indicator.cfm?i=23#2

US VOC Emissions Strong temperature dependence of BV

Biogenic

Anthro.

Increased T Increased Biogenic VOC Emissions Increased Pollution

24 hr ave secondary PM2.5 (BSOA) increased by up to 1 µg m-3

Cumulative Distribution of MDA 8hr O3

(Chen et al. AE 2009)

Effects of Changes in Land Use and Land Cover

(Chen et al. AE 2009)

Current

Land Use

Future

Changes in BVOC EmissionsHigher

Lower

Changes in O3 Changes in PM2.5

GOES-16 satellite visible image from September 4, 2017 https://www.aos.wisc.edu/

Wildfires

Increases in wildfires driven by changes in climate

Westerling, Increasing western US forest wildfire activity: sensitivity to changes in the timing of spring, Phil. Trans. R. Soc. B, 2016.

r2 = 0.48p < 0.001

What might smoke be like in the future? What impact on mortality might it have?

Westerling, Increasing western US forest wildfire activity: sensitivity to changes in the timing of spring, Phil. Trans. R. Soc. B, 2016.

r2 = 0.48p < 0.001

Future: 50-100% increase in fires?

Predicted PM2.5 from fire smoke greatly increases

2000 2100

Annual-mean PM2.5 from wildfire smoke onlyUnpublished results from Jeff Pierce @ Colorado State Univ.

Jeff Pierce @ CSU

Anthropogenic emissions are falling

Fiore et al. Chem Soc Rev 2012

CH4 SO2

BCNO

NH3

RCP scenarios for traditional pollutants

PM2.5 -- changes in anthropogenic emissions generally swamp climate and land use effects

(Val Martin et al. ACP 2015)

Will fires offset PM2.5 reductions from anthropogenic emissions?

(Val Martin et al. ACP 2015)Summertime levels?

Ozone: Emissions more important than meteorology factors

Climate change “penalty” Emissions cuts (SRES B1)

(Rac

herla

and

Adam

s ES

T 20

08)

Linkages between climate and air pollution policies

• 50,000 people per year dying the US from air quality. VSL 100s of billions per year. Few percent of GDP.

• Health benefits, from e.g. increased natural gas use, can cover 10-30% climate change mitigation for free

(Thompson al. Nat Climate Change 2014)

Polic

y co

sts c

over

ed b

y he

alth

(%)

CO2 reduction (%)

Linkages between climate and air pollution policies

• 50,000 people per year dying the US from air quality. VSL 100s of billions per year. Few percent of GDP.

• Health benefits, from e.g. increased natural gas use, can cover 10-30% climate change mitigation for free

• Challenges:• Could you get air quality benefits other ways?

E.g. cheaper end of pipe in short term• Private versus social costs• Very different time scales• We are already doing many of these things.

(Thompson al. Nat Climate Change 2014)

Polic

y co

sts c

over

ed b

y he

alth

(%)

CO2 reduction (%)

coal gas

NOx (g NO2/kWh)0.76

0.12

coal gas

CO2 (g CO2/kWh)

911

424

US Electricity Generation

Air Pollutant Emissions

DOE EIA

(de Gouw et al. Earth’s Future, 2014)

Natural Gas & US Electricity Production

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Frac

tion

of U

S El

ectr

icity

Gen

erat

ion

Natural Gas

Coal

Nuclear

HydroRenewable

50%

17%33%

30%

Natural gas drill rigs in Hopewell Township, news.nationalgeographic.com

What about local impacts?

Gasoline Direct Injection (GDI) vehicles are being rapidly adopted to meet fuel economy standards

GDI = Gasoline Direct InjectionPort Fuel Injection (PFI)

GDI Benefits:(1) Higher compression ratio due to evaporative cooling effect

reducing compression temperature and knock onset(2) Greater flexibility in valve operations

~5% higher fuel economy

(Zim

mer

man

et a

l. ES

T 20

16)

Gasoline (PFI) vehicle PM emissions falling

(Sal

iba

et a

l. ES

T 20

17)

1990 2000 2010 2020

ULEV SULEVLEV

~10x

(Sal

iba

et a

l. ES

T 20

17)

1990 2000 2010 2020

GDI ~ 2xPFI

ULEV SULEVLEV

GDI ~ 3xPFI

GDI vehicles have higher PM emissions

GDI: Health costs > climate benefits

Analysis for Los Angeles Area using EMFAC emissions and

EASIUR social cost of PM

Social cost of carbon: $37/ton

GDI: Health costs > climatebenefits

Analysis for Los Angeles Area using EMFAC emissions and

EASIUR social cost of PM

Social cost of carbon: $37/ton

Carbon Capture and Sequestration (CCS)

CCS Ammonia Slip and Air Quality

• Social cost of CCS ammonia: $31-$68/t-CO2

• Social cost of carbon: $28-$102/t-CO2

• Ammonia emissions not too difficult to control

(Heo

et a

l. ES

T 20

15)

PM2.5 increase from capturing 2 Gt-CO2(~ current coal emissions) in 2050

Conclusions• Complex interplay of climate change and air pollution

• Meteorology • Natural Emissions

• Large reductions in anthropogenic emissions will likely win!

• But Climate penalties degrade benefits

• Lots of interesting technology scenarios• Health benefits of some mitigation options can cover

some climate mitigation cost