1. Recent and predicted changes in atmospheric composition over the United States from climate, emissions and bark beetles Fall AGU Meeting December 6, 2012 Colette L. Heald Ashley Berg and Maria Val Martin Acknowledgements: Arjan Meddens, Jeff Hicke, Kara Huff-Hartz, Gannet Haller, Jean-Francois Lamarque, Simone Tilmes, Louisa Emmons

2. EMISSIONS (natural & anthropogenic) CLIMATE LAND USE CHANGE (natural & anthropogenic) TROPOSPHERIC COMPOSITION (Global CESM model)

3. NEW IPCC PROJECTIONS SUGGEST DRAMATIC CHANGES IN ANTHROPOGENIC EMISSIONS AND LAND USE OVER THE U.S. U.S. Anthropogenic Emissions (Tg Species/year) Aggressive reductions in anthropogenic emissions in all RCP scenarios (except NH 3 ). GHG emission increases also drive warming climate and changes in natural emissions… Changes in land cover projected for 2050 (RCP 4.5) % Trees % Crops

4. ∆Climate∆Land Use Important decrease in NO x emissions RCP4.5 SCENARIO PROJECTS A LARGE DECREASE IN SURFACE O 3 DUE TO NO x EMISSION REDUCTIONS ∆Anthro Emissions RCP4.5 2050-2000 Summer Surface O 3

5. RCP8.5 Climate and land cover changes may offset the benefits of emission reductions, similar to A1B projections (Wu et al., 2008) RCP8.5 SCENARIO SURFACE O 3 REDUCTIONS, MORE MODEST DUE TO COMPENSATION FROM CLIMATE/LAND USE Important decrease in NO x emissions ∆Climate∆Anthro Emissions∆Land Use 2050-2000 Summer Surface O 3

6. East US West US Annual Changes in PM 2.5 Chemical Speciation PREDICTED REDUCTION IN SURFACE PM 2.5 IS ALMOST ENTIRELY DRIVEN BY SO 2 and NO x EMISSION REDUCTIONS RCP 4.5 2050-2000 Surface PM *Large decreases in NH sulfate shown by Chalmers et al. (2012) to potentially lead to rapid warming

7. WHAT ABOUT INCREASES IN PM DUE TO FIRE ACTIVITY? 2000 2050 Increased area burned results in ~150% increase in BC and OC fire emissions Projected annual total biomass burned Yue et al, in review JGR Changes in summer PM 2.5 from fires alone Future PM 2.5 may stay constant over western US due to increased fire activity! PM2.5 PM2.5 Fires [val Martin et al., in prep]

8. BARK BEETLE INFESTATION IN WESTERN NORTH AMERICA Worst beetle outbreak in recorded history: peaked in BC in 2007 and in the Western US in 2009 [Kurz et al., 2008] Over 100,000 km 2 of forest killed, continued expansion. Impacts: carbon cycling, fire susceptibility. What about air quality?

9. VOCs ↓ Mortality Effect ↑ Attack Effect VOCs? O3O3 BARK BEETLES PERTURBING MONOTERPENE EMISSIONS Very few quantitative studies have been done Amin et al. (2012) measure emissions from Lodgepole pine (and spruce) under attack by mountain pine beetle, see significant enhancements of some emissions.

10. ESTIMATED IMPACTS ON MONOTERPENE EMISSIONS Largest impact of MPB on monoterpene emissions in British Columbia in 2004 (increase up to 70%) and in 2008 in US (increase up to 104%). Mortality Effect Mortality Effect + Attack Effect VEGETATION DISTRIBUTIONS (CLM4) ANNUAL MORTALITY (Meddens et al., in press) EXPERIMENTAL VOC INCREASES (Amin et al., 2012) VOC EMISSIONS IN CLM4 (MEGAN2.1) (Guenther et al., in press) β-pinene, β-phellandrene, 3-carene, P-cymene 2004 2008

11. ESTIMATED IMPACTS ON SOA FORMATION [Berg et al., ACPD, 2012] Mortality Effect Mortality Effect + Attack Effect 2004 2008 VEGETATION DISTRIBUTIONS (CLM4) ANNUAL MORTALITY (Meddens et al., in press) EXPERIMENTAL VOC INCREASES (Amin et al., 2012) VOC EMISSIONS IN CLM4 (MEGAN2.1) (Guenther et al., in press) CHAMBER SOA YIELDS (6-55%) (Lee et al., 2006) More muted impact on SOA (~30-40% max increases) but also more regional. Dependent on very uncertain species- variable response: scenario using spruce data shows up to doubling of SOA (1 µgm -3 increase). This is comparable to the estimate of “natural” aerosol background  implications for achieving EPA Regional Haze Rule Evidence of importance of land use change in air quality.

12. Near-term air quality over the US very likely to improve (both O 3 and PM 2.5 ) based on new RCP scenarios (see CMIP5 results: Fiore et al., 2012) Bark beetle infestation of the last decade has likely led to significant changes in BVOC emissions and OA in Western North America (larger than projected emissions, climate and land use impacts on SOA in the next century previously estimated (Heald et al., 2008; Wu et al, 2012), with implications for visibility in remote regions. Land use change (wildfires, beetles, etc.) is the most challenging driver of atmospheric composition to predict, and is a key uncertainty in chemistry-climate projections CONCLUSIONS