1. Global Linkages Between Vegetation, Atmospheric Composition and Climate Fall AGU Meeting, San Francisco December 19, 2008 Colette L. Heald Acknowledgements: Dominick Spracklen, Russ Monson, Mick Wilkinson, Clement Alo, Guiling Wang, Alex Guenther, Daven Henze, Larry Horowitz, Johannes Feddema, Jean-Francois Lamarque, Peter Hess, Francis Vitt, John Seinfeld, Allen Goldstein, Inez Fung

2. DISTURBANCE: Fires, beetles, land use change EMISSIONS: Particles Organics NOx … + oxidants + oxidation O3O3 ANTHROPOGENIC INFLUENCE ↓ OH = ↑ CH 4 lifetime + FEEDBACKS FROM CLIMATE CHANGE (moisture, precipitation, T, hv) ? PBAP SOA C5H8C5H8

3. FUTURE PREDICTION OF SECONDARY ORGANIC AEROSOL Sources may be large(?), how MIGHT they change? ZONAL MEAN SOA CONCENTRATIONS: 2100-2000  (ANTHROPOGENIC EMISSIONS): POA (partitioning) Aromatics (precursor) Trace gases (NOx, oxidants)  (BIOGENIC EMISSIONS): BVOC (precursor)  (CLIMATE): Precipitation (lifetime) T (partitioning, oxidation) Convection (distribution, lifetime) Lightning (NOx aloft) Water vapour (P OH )  (ANTHROPOGENIC LAND USE) Climate impact is complex/compensatory/uncertain. Predict large increase in SOA burden (> 20%) tied to T-driven BVOC emissions, with large sensitivity to future land use. Global Model: NCAR CAM3-CLM3 (2  x2.5  ) [Heald et al., 2008]

4. METEOROLOGICAL AND PHENOLOGICAL VARIABLES CONTROLLING ISOPRENE EMISSION LIGHT  Diffuse and direct radiation  Instantaneous and accumulated (24 hrs and 10 days) TEMPERATURE (Leaf-level)  instantaneous and accumulated (24 hrs, 10 days) T PAR LL TT [Guenther et al., 2006] SOIL MOISTURE  suppressed under drought AMOUNT OF VEGETATION  Leaf area index (LAI) Month LAI SUMMER LEAF AGE  Max emission = mature  Zero emission = new E isoprene ≈ E CH4

5. ISOPRENE IN THE FUTURE Isoprene emissions projected to increase substantially due to warmer climate and increasing vegetation density.  LARGE impact on oxidant chemistry and climate  20002100 NPP ↑ Temperature↑ Surface O 3 ↑ 10-30 ppb [Sanderson et al., 2003] Methane lifetime increases [Shindell et al., 2007] SOA burden ↑ > 20% [Heald et al., 2008]

6. CO 2 INHIBITION COMPENSATES FOR PREDICTED TEMPERATURE-DRIVEN INCREASE IN ISOPRENE EMISSION CONCLUSION: Isoprene emission predicted to remain ~constant Important implications for oxidative environment of the troposphere… * With fixed vegetation 508 523 696 479 E isop (TgCyr -1 ) 20002100 (A1B) MEGAN MEGAN with CO 2 inhibition Global Model: NCAR CAM3-CLM3 (2  x2.5  ) Empirical parameterization from plant studies [Wilkinson et al., GCB, in press]

7. UNLESS…CO 2 FERTILIZATION IS STRONG CLM DGVM projects a 3x increase in LAI associated with NPP and a northward expansion of vegetation. [Alo and Wang, 2008]  Isoprene emissions more than double! (1242 TgCyr -1 ) BUT, recent work suggests that NPP increases may be overestimated by 74% when neglecting the role of nutrient limitation [Thornton et al., 2007] [Heald et al., GCB, in press]

8. PRIMARY BIOLOGICAL AEROSOL PARTICLES (PBAP) POLLEN BACTERIA VIRUSES FUNGUS ALGAE PLANT DEBRIS How much does this source contribute to fine-mode OC? Jaenicke [2005] suggests may be as large a source as dust/sea salt (1000s Tg/yr) Elbert et al. [2007] suggest emission of fungal spores ~ 50 Tg/yr LARGE particles (> 10 µm)

9. PRELIMINARY EMPIRICAL PBAP SIMULATION Elbert et al. [2007] identify that mannitol is a tracer for fungal spores 1 pg mannitol = 39 pg OM* Global Model: GEOS-Chem (2  x2.5  ) Emission = constant [Elbert al., 2007] Emission = f(LAI, H 2 O) A number of meteorological drivers could be expected to modulate fungal PBAP emissions. Here we find LAI and atmospheric water vapour concentrations are the best predictors for observed average mannitol concentrations. Test a series of meteorological drivers for mannitol emission. BEST MATCH PBAP OA (PM2.5)

10. FUNGAL PBAP CONTRIBUTES <10% TO FINE-MODE OA SOURCE Global Annual Emissions: 2003 66 30 POASOAPBAP fine PBAP coarse < 2.5  m 2.5-10  m Tg 21 7 Global Model: GEOS-Chem (2  x2.5  ) Annual Mean Surface Concentrations Consistent with AMS observations from AMAZE where OA concentrations were low. Need more PBAP observations! [Heald and Spracklen, in prep]

11. CHALLENGES FOR UNDERSTANDING IMPACT OF VEGETATION ON COMPOSITION & CLIMATE AT THE GLOBAL SCALE 1.Land Use (Present/Future) 2.Species Diversity 3.Connecting scales: SCALE UP? HOW MUCH IS THERE???