Havala Olson Taylor Pye

April 11, 2007Seinfeld GroupDepartment of Chemical EngineeringCalifornia Institute of Technology

The Effect of Climate Change on Secondary Organic Aerosols

Outline

Introduction

Model and Simulation Description

Predicted Present Day SOA Concentrations

The Effect of Climate Change on SOA

Conclusions

IntroductionOrganic aerosol consists of Primary Organic Aerosol (POA) Secondary Organic Aerosol (SOA)

SOA in GEOS-Chem is of biogenic origin and potentially influenced by changes in

Temperature (affects partitioning and precursor emission rates)

Precipitation and atmospheric stability Transport Gas phase chemistry (such as oxidant levels)

Objective: Determine the effect of climate change on SOA

Model and Meteorological Field DescriptionApproach for examining the effect of climate change on SOA: Simulate present day (1999-2001) aerosol (sulfate, nitrate,

ammonium, sea salt, black carbon, organic carbon) levels Meteorology from GISS GCM III Simulations with GEOS-Chem v.7-04-05 (full chemistry)

Simulate future (2049-2051) aerosol levels Meteorology from GISS GCM with CO2 emissions following IPCC

A1B scenario Simulations with GEOS-Chem assume anthropogenic emissions

remain at present day levels

The meteorology of the future [Wu et al. in preparation 2007]

522 ppm CO2 in 2050 1.7 K global mean surface temperature rise 8% increase in global annual mean precipitation

SOA Model

SOAProduction from oxidation of gas phase precursors

SOGEquilibrium Partitioning

Wet deposition

Dry deposition

Wet deposition

Dry deposition

SOA is represented using a

two (or one) product model:

Parameters obtained from laboratory experiments: αi , KOM,i

SOA Model

HC + Ox α1G1 + α2G2

A1 A2 Oi

iiOM MG

AK

][

][,

O

i

OOiOMiOM TTR

H

T

TTKTK

11exp)()( ,,

i

iO APOAM ][][

[Chung and Seinfeld, 2002; Pankow, 1994]

SOA Precursors

Parent VOC categories treated by GEOS-Chem

(I) ALPH: α-pinene, β-pinene, sabinene, careen, terpenoid ketones(II) LIMO: limonene(III) TERP: α-terpinene, γ-terpinene, terpinolene(IV) ALCO: myrcene, terpenoid alcohols, ocimene(V) SESQ: sesquiterpenes(VI) ISOP: isoprene

Biogenic Emission SchemeEmissions are potentially influenced by climate through

temperature and changes in light received at the surface

Monoterpenes (I-IV): No light dependence

ORVOC (I, IV, V): CL independent of climate

change No T dependence

Isoprene (VI): CL depends on column cloud

cover

E = EO CT CL

[Guenther et al., 1995]

Predicted Present Day SOA Concentrations

DJF MAM

JJA SON

Predicted Present Day SOA Concentrations: The U. S.

DJF MAM

JJA SON

The Effect of

Climate Change on SOA

The Effect of Temperature on Biogenic Emissions

Isoprene emissions increase 24%

Monoterpene emissions increase 20%

SOA category

Contributing Emissions

Present Day

FuturePercent Change

Tg/yr Tg/yr

ALPHMonoterpenes,

ORVOC 111 131 18%

LIMO Monoterpenes 34 40 20%

TERP Monoterpenes 4 5 20%

ALCOMonoterpenes,

ORVOC 40 42 5%

SESQ ORVOC 15 15 0%

ISOP Isoprene 505 629 24%

Changes in SOA Surface Concentrations

Changes in SON Surface Concentrations (preliminary analysis) Significant decreases likely correspond to moderate temperature

increases coupled with strong increases in precipitation Increases in surface concentrations likely correspond to

strong temperature increases or moderate temperature increases coupled with reduced rainfall

(except for possibly S. America)

Changes in SOA as a Function of Altitude

The Effect of Climate Change on

SOA Global Burdens Climate change does not significantly affect the global SOA burden

The burden decreases if biogenic emissions do not increase

burdenwet

depositionnet

production

dry depositio

n

Tg Tg/yr Tg/yr Tg/yr

present 0.44 -14 17 -3

future 0.45 -16 19 -3

burdenwet

deposition

net productio

n

dry depositio

n

Tg Tg/yr Tg/yr Tg/yr

present 0.020 -0.98 1.21 -0.23

future 0.016 -0.95 1.17 -0.23

SOA from sesquiterpenes

Conclusions Higher temperatures in the future result in higher

biogenic emissions

In general, surface SOA concentrations are elevated in the future due to increased precursor emissions

Increased precipitation may cause decreased surface concentrations

Concentrations of SOA in the upper troposphere are typically lower in the future

Despite changes in concentrations, the SOA global burden remains constant with 2000—2050 climate change

Acknowledgements

Meteorological fields were provided by Loretta Mickley. Useful discussions with Shiliang Wu and Hong Liao are greatly appreciated. This material is based upon work supported under a National Science Foundation Graduate Research Fellowship.

References: Chung, S. H. and J. H. Seinfeld (2002), Global distribution and climate forcing of

carbonaceous aerosols, J. Geophys. Res., 107, D19, 4407. Guenther, A., et al. (1995), A global model of natural volatile organic compound

emissions, J. Geophys. Res., 100, D5, 8873-8892. Pankow, J. F. (1994), An absorption model of gas/particle partitioning of organic

compounds in the atmosphere, Atmos. Environ., 28, 185-188. Wu, S., L. J. Mickley, D. J. Jacob, D. Rind, and D. G. Streets (2007), Effect of 2000-

2050 global change on ozone air quality in the United States, in preparation .