Havala Olson Taylor Pye April 11, 2007 Seinfeld Group Department of Chemical Engineering California 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

Introduction Organic 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 Description Approach for examining the effect of climate change on SOA: Simulate present day ( ) aerosol (sulfate, nitrate, ammonium, sea salt, black carbon, organic carbon) levels  Meteorology from GISS GCM III  Simulations with GEOS-Chem v (full chemistry) Simulate future ( ) aerosol levels  Meteorology from GISS GCM with CO 2 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 CO 2 in 2050  1.7 K global mean surface temperature rise  8% increase in global annual mean precipitation

SOA Model SOA Production from oxidation of gas phase precursors SOG Equilibrium Partitioning Wet deposition Dry deposition Wet deposition Dry deposition

SOA is represented using a two (or one) product model: Parameters obtained from laboratory experiments: α i, K OM,i SOA Model HC + Ox α 1 G 1 + α 2 G 2 A 1 A 2 [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 Scheme Emissions 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): C L independent of climate change No T dependence Isoprene (VI): C L depends on column cloud cover E = E O C T C L [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 categoryContributing Emissions Present Day Future Percent Change Tg/yr ALPHMonoterpenes, ORVOC % LIMOMonoterpenes344020% TERPMonoterpenes4520% ALCOMonoterpenes, ORVOC40425% SESQORVOC15 0% ISOPIsoprene %

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 deposition net production dry deposition TgTg/yr present future burdenwet deposition net production dry deposition TgTg/yr present future 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, Guenther, A., et al. (1995), A global model of natural volatile organic compound emissions, J. Geophys. Res., 100, D5, Pankow, J. F. (1994), An absorption model of gas/particle partitioning of organic compounds in the atmosphere, Atmos. Environ., 28, Wu, S., L. J. Mickley, D. J. Jacob, D. Rind, and D. G. Streets (2007), Effect of global change on ozone air quality in the United States, in preparation.