Predicted change in global secondary organic aerosol concentrations in response to future climate, emissions, and land use change

C L Heald,J H Seinfeld,F Vitt,P G Hess,D K Henze,A Guenther,J.-F Lamarque,L W Horowitz,I Fung,J Feddema,A H Goldstein

doi:10.1029/2007jd009092

Abstract

The sensitivity of secondary organic aerosol (SOA) concentration to changes in climate and emissions is investigated using a coupled global atmosphere‐land model driven by the year 2100 IPCC A1B scenario predictions. The Community Atmosphere Model (CAM3) is updated with recent laboratory determined yields for SOA formation from monoterpene oxidation, isoprene photooxidation and aromatic photooxidation. Biogenic emissions of isoprene and monoterpenes are simulated interactively using the Model of Emissions of Gases and Aerosols (MEGAN2) within the Community Land Model (CLM3). The global mean SOA burden is predicted to increase by 36% in 2100, primarily the result of rising biogenic and anthropogenic emissions which independently increase the burden by 26% and 7%. The later includes enhanced biogenic SOA formation due to increased emissions of primary organic aerosol (5–25% increases in surface SOA concentrations in 2100). Climate change alone (via temperature, removal rates, and oxidative capacity) does not change the global mean SOA production, but the global burden increases by 6%. The global burden of anthropogenic SOA experiences proportionally more growth than biogenic SOA in 2100 from the net effect of climate and emissions (67% increase predicted). Projected anthropogenic land use change for 2100 (A2) is predicted to reduce the global SOA burden by 14%, largely the result of cropland expansion. South America is the largest global source region for SOA in the present day and 2100, but Asia experiences the largest relative growth in SOA production by 2100 because of the large predicted increases in Asian anthropogenic aromatic emissions. The projected decrease in global sulfur emissions implies that SOA will contribute a progressively larger fraction of the global aerosol burden.

Highlights

[2] Organic carbon aerosol is a dominant component of observed submicron particulate matter, with contributions ranging from 20 to 90% [Kanakidou et al, 2005]
secondary organic aerosol (SOA) from monoterpenes is most important in the boreal regions in summertime
SOA condensation is favored at cold temperatures, and precursors aloft can efficiently be converted to aerosol form, providing an in situ free tropospheric source, unlike primary organic aerosol (POA)

Summary

Introduction

[2] Organic carbon aerosol is a dominant component of observed submicron particulate matter, with contributions ranging from 20 to 90% [Kanakidou et al, 2005] These aerosols can be directly emitted (primary) or formed in the atmosphere (secondary) following the oxidation of volatile organic compounds (VOC). Precursors of secondary organic aerosols (SOA) include both anthropogenic and biogenic compounds, emissions of which are expected to rise as a [3] The yields of SOA from the condensation of semivolatile oxidation products of VOCs have been extensively studied in laboratory chambers. The range of chemical and physical environments represented by these studies suggests that the mechanisms and precursors contributing to SOA formation are diverse In light of these discrepancies, previous estimates of the global source of SOA (12 – 40 Tg C aÀ1 [IPCC, 2001]) are likely to be an underestimate. Explore how aerosol composition, including SOA, has changed since preindustrial times. Liao et al [2006] predict a 54% increase in SOA from terpene oxidation in 2100 as a result of changes in climate and anthropogenic emissions from the IPCC A2 emission scenario. Tsigaridis and Kanakidou [2007] use a chemical transport model to investigate how SOA responds to emissions changes in the IS92a scenario, and predict han a doubling of the global

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Conclusion