Carbonaceous aerosols and climate change Carbonaceous aerosols and climate change over Asia for the 1980-2030 time periodover Asia for the 1980-2030 time period

Surabi MenonLawrence Berkeley Laboratory, Berkeley, CA, USA

smenon@lbl.gov

Dorothy Koch and Nadine UngerColumbia University/NASA GISS, NY, USA

University of Vermont, VE, USADavid Streets

Argonne National Laboratory, Argonne, IL, USA

Better Air Quality WorkshopYogyakarta, Indonesia, December 13-15, 2006

Aerosol-Climate/Air Quality Effects: 1980, Present-day, 2030A1B A1B scenario: Balanced mix of technology and supply, no dominant single source of energy.

Role of Black Carbon Aerosols

Regional Signals Climate Sensitivity, Radiative forcing, Surface mass, Temperature, Precipitation

Sensitivity Study Increase carbonaceous emissions from transportation and biofuel to 2x 2030A1B for Asia: 10S to 40 N and 58 to 120 E.

Outline

Why focus on Aerosol-Climate Effects?

Aerosol climate effects: +0.8 to – 2.1 Wm-2

Greenhouse gas climate effects: +2.96 Wm -2

(Menon 2004, Ann. Rev.)

(Hansen et al. 2005, JGR)

Schematic of direct & indirect aerosol effects

Aerosol indirect effect=

Change in Cloud properties due to aerosol impacts on

clouds

Direct effect =Scattering/Absorption ofradiation w/o clouds

Modified from Lohmann (2005)

Aerosols and air quality over China and India

Regional measurements of OC/BC over 4 cities in PDRC (Cao et al., 2004.)

• ~ 1/3 of PM 2.5/10 mass were carbonaceous. PM2.5: OC = 9.2 and BC = 4.1 g m-3

PM10 : OC =12.3 and BC = 5.2 g m -3 • No strong seasonal fluctuations in OC and BC.

• Motor vehicle emissions === major source.

Over India: Particulate matter more important than NOx or SO2.

• Biofuels/fossil fuel combustion major contributor to deteriorating air quality. (Mitra and Sharma, 2002).

• BC source ratio (biofuel/total) ~ 44% in India compared to 15% globally (Venkataraman et al. 2005).

OC=Organic Carbon BC =Black carbon

Black Carbon Sources and Distribution

Black carbon is a product of

incomplete combustion.

Images: http://www.asthmacure.com, NASA GSFC

Fossil/bio-fuel = 0.08 0.07

Biomass = 0.07 0.06

1995 2030A1BBurden(Tg)

Over Asia: 10S-40N, 58-122E

Fossil/bio-fuel = 0.22 0.17

Biomass = 0.04 0.05

1995 2030A1BBurden(Tg)

Forcing efficiencies: 2030A1B to 1995

Differences between 2030A1B and 1995 aerosol emissions

*Forcing efficiency= Direct forcing Aerosol mass column burden (mg m-2)

Case Sulfate OC BC BC Total

(Total) (Fossil/biofuel/

biomass)

(Fossil/bio-fuel)

(Biomass)

Direct Forcing (Wm -2)

-0.23 +0.02 -0.03 -0.02 -0.26

* Forcing efficiency (W g-1)

-203 -77 882 1000

Forcing efficiencies: 2030A1B to 1995

Differences between 2030A1B and 1995 aerosol emissions

*Forcing efficiency= Direct forcing Aerosol mass column burden (mg m-2)

Case Sulfate OC BC BC Total

(Total) (Fossil/biofuel/

biomass)

(Fossil/bio-fuel)

(Biomass)

Direct Forcing (Wm -2)

-0.23

-0.24

+0.02

0.00

-0.03

+0.07

-0.02

-0.02

-0.26

-0.19

* Forcing efficiency (W g-1)

-203

-198

-77

-

882

1458

1000

1000

Differences between 2030A1B_A and 1995 aerosol emissions

Climate Sensitivity: Black Carbon

Calculate the ratio of surface temperature change to forcing for 2030 versus 1995 aerosol emissions. Ratio is a lower limit to climate sensitivity w/o a coupled ocean-atmosphere model.

Transportation & biofuel black & organic carbon

Climate sensitivity (K W-1m2)

Standard -2.58 (0.67/-0.26)

2x (40%) -3.53 (0.67/-0.19)

Standard w/o BC/OC (10%) -2.37 (0.64/-0.27)

Standard + Qflux (50%) -3.88 (0.97/-0.25)

Hadley Center climate model: 4 x fossil fuel Black Carbon:

Climate sensitivity (Present day to 1850) = 0.56 K W-1m2

Climate sensitivity to doubled CO2 is ~ 0.91 K W-1m2.

(Roberts and Jones, 2004, JGR).

China: Black Carbon and Summer Monsoon Trends

Without black carbonWith black carbon

Over the last few decades:

• increased floods/droughts in the south/north; increased dust storms in the spring;• precipitation trends largest observed since 950 AD.

We link increased emissions over China (since the late 1970’s) with observed climate.Assume a large proportion of aerosols are absorbing (black carbon).Changes in heating profile affects convective fluxes, stability and spatial redistribution of precipitation.

(Menon et al. 2002, Science)

Industrial Pollution: Shenyang, China, and India/Nepal

Image courtesy:Image Analysis Laboratory, NASA Johnson Space Center

Astronaut photograph ISS010-E-13807, acquired January 18, 2005

Hun River

Industrial Plumes

Snow cover change between urban and rural areas

Aerosol optical depth from satellite (MODIS), Dec 2002

•Aerosol visible optical depths ~ 0.6 •Aerosol single scattering albedo ~ 0.78•Inferred shortwave atmospheric forcing ~ 25 W m-2

(Ramana et al. 2004, GRL)

Future Emission Trends: A cause for concern

• SO2 emissions in China and Korea for an A1B scenario for 2020 exceed targets.

• BC emissions in China for 2000 are very large (2.3 Tg/yr) compared to Japan (0.053 Tg/yr)

Street et al. 2002, Akimoto 2003, Image source from D. Alles

• NOx emissions are rising in AsiaAlso confirmed by recent satellite estimates from Schiamachy that show high NO2 columns over major cities.

• Every 1 g m-3 increase in BC causes a 3.5 g m-3 reduction in O3 -----Surface reactions on soot. (Latha and Badarinath, 2004.)

Based on Jan 2004 data over Hyderabad, India.

Annual mean radiative forcing over China :

Anthropogenic BC: 5.0 W m-2

Anthropogenic O3: 0.5 W m-2

25 ppm increase in CO2: 0.1 W m-2

(Chung and Seinfeld, 2005)

Future Climate (2030-1995)

Global annual amount and change in surface amount

(ppbv)

1995 Surface Ozone 26.42 3.43Change in Surface Ozone

Future Climate (2030-1995)

Average: 10S to 40N, 58 to 122E

Aerosol direct forcing = -0.26 W m-2

Ozone forcing = 0.12 W m-2 1980 1995 2030A1B 2030A1B

A

BC 0.33 0.32 0.27 0.37

OC -0.17 -0.17 -0.15 -0.17

Sulfate

-0.68 -0.64 -0.87 -0.88

Total

Ozone

-0.52

-0.37

-0.49

-0.37

-0.75

-0.25

-0.68

Aerosol direct forcing = -0.50 W m-2

2x BC/OC = -0.48 W m-2

Ozone forcing = 0.24 W m-2

= 0.25 W m-2

Global

Future Climate (2030-1995)

Average: 10S to 40N, 58 to 122E

Aerosol direct forcing = -0.26 W m-2

Ozone forcing = 0.12 W m-2

Aerosol direct forcing = -0.50 W m-2

2x BC/OC = -0.48 W m-2

Ozone forcing = 0.23 W m-2

= 0.25 W m-2

Global

Without carbonaceous aerosols, Ozone forcing = 0.15 W m-2

===> 20% increase in ozone forcing, globally

Over Asia, increase in ozone forcing is ~4%==> no net benefit from BC/OC

Future climate/air quality changes

Time Period Ozone(ppbv)

AerosolMass(gm-3)

Net Rad. Sfc/TOA(Wm-2)

Ts(K)

2030A1B-1995

8.28 4.19 -2.5/-3.84 0.46

2030A1B_A - 1995

8.35 13.6 -3.25/-3.58 0.52

Average difference: 10S to 40N, 58 to 122E

Health effects from increase in ozone amount and particulate matter??

-0.91 0.23

Calculate linear trend in absorbed solar radiation for 1960 to 2002:Exp A: All forcings (ozone, land-use, snow/ice albedo change, solar, GHG, water vapor, aerosols)Exp B: Similar to Exp A but no anthropogenic aerosols

Anthropogenic Aerosol Effects:1960-2002

(Nazarenko and Menon 2005, GRL)Units (W m-2); Global means: r.h.s of graph

“Global dimming: 1960-1990; Reversal after 1990”

Exp A Exp B

Surface Temperature Trends: 1960-2002

Units in K; Global means: r.h.s. of graph

With anthropogenic aerosols, temperaturetrends (Exp A) match observed trends.

Policy Implications: Without mitigating both GHGs and aerosols, sfc. temp. reduction due to aerosols may no longer mask GHG effects in some regions if only aerosols are reduced, as in Europe & U.S.

0.50 0.77

0.52Obs.

Summary

Carbonaceous aerosols from industrial/biofuel sources have important regional climate effects especially over Asia:

1. Ratio of change in surface temperature to radiative forcing increase by 40% if biofuel/transportation black carbon increases by a factor of 2.

2. Black carbon induced heating within the atmospheric column changes spatial pattern of precipitation.

Future air quality change: 2000 to 2030 • Ozone and aerosol effects over Asia is twice the global average and especially strong over tropical regions such as India.• With addition of carbonaceous aerosols, ozone forcing ~ 20% for 2030, butnot much benefit for Asia.Health and air quality issues will becoming increasingly important for Asia!

Large unknown in climate change: Emission sources, Interactions and feedbacks of the climate system.

Based on CO2 and temperature response, emission pathways may change:

• Industrial aerosol emissions are linked to technological change and economic projections,• If future emissions change, climate response is going to depend on regional changes and

the impact on distant climate.

Future Predictions and link to climate

0

5

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25

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Transport Industry Residential Power Biomass

Tg/

yr

BCOMSO2

Global emissions

(Koch et al. 2006, JGR)

0

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35

Transportation Industrial Residential Commercial

US CO2

Emissions

(Hansen et al. 2004)