Geophysical Fluid Dynamics Laboratory Review June 30 - July 2, 2009

Climate and Air Quality Presented by Arlene Fiore

Methane emission reduction potential (Mton CH4 yr-1) Addressing air quality and climate via methane emission controls: A viable option? Cost-saving Cost-effective All identified (industrialized nations) METHANE CONTROL OPTIONS 10% of anth. emissions 20% of anth. emissions 0 20 40 60 80 100 120 Methane emission reduction potential (Mton CH4 yr-1) IEA [2003] for 5 industrial sectors ~25% of global anthropogenic emissions at cost-savings / low-cost (West and Fiore, 2005) 3

Decreasing methane lowers global surface O3 background Range across 18 models  Robust result across models N. Amer. Europe E. Asia S. Asia N. Amer. Europe E. Asia S. Asia Intercontinental emission controls: CH4 ≈ NOx+NMVOC+CO  Domestic emission controls: NOx+NMVOC+CO more effective -20% Foreign Anthrop. Emissions -20% Domestic Anthrop. Emissions (Results from TF HTAP model intercomparison; Fiore et al., 2009) 4

Benefits from CH4 controls to climate and air quality: Decreased radiative forcing and high-O3 events Methane emission reductions are applied to BASE emission scenario (2005 to 2030 full-chemistry transient simulations in MOZART-2) CLIMATE AIR QUALITY Net Forcing Percentage of model grid-cell days where surface ozone (MDA8) > 70 ppbv BASE 2005 BASE 2030 CH4 CONTROL CH4=700 ppb (W m-2) OZONE METHANE Cost-effective controls prevent increase in O3 > 70 ppbv in 2030 relative to 2005 in Europe BASE CH4=700 ppb CH4 CONTROL (Fiore et al., 2008) 5

Climate sensitivity: Small increases in temp Climate sensitivity: Small increases in temp. and OH shorten the methane lifetime Contributions to change in methane lifetime from 1991-1995 to 2000-2004 in BASE Global mean surface methane (ppb) DT(+0.3K) + = DOH(+1.2%) BASE Decrease in methane lifetime (years) OBSERVED BASE (constant emis.) ANTH (time-varying) ANTH+BIO (time-varying) (Fiore et al., 2006) 6

Summary: Connecting climate and air quality via O3 & CH4 CLIMATE AND AIR QUALITY BENEFITS FROM CH4 CONTROL Decreased hemispheric background O3 (robust across models) Complementary to NOx, NMVOC controls Independent of reduction location (but depends on NOx) IMPACT OF CHANGING CLIMATE ON METHANE TRENDS ? 1990 to 2004 model trend driven by increasing T, OH Trends in global lightning activity? Other potential climate feedbacks (on sources and sinks) (Fiore et al., 2002, 2006; West and Fiore, 2005; Fiore et al., 2008, 2009) 7

NEW DIRECTION: Impact of Future Changes in Climate on Air Quality 20-year AM3 simulations with annually-invariant emissions of ozone and aerosol precursors (except for lightning NOx), to isolate role of climate change Present Day Simulation (“1990s”): observed SSTs and sea ice (1981-2000 mean) Future Simulation (“A1B 2090s”): observed SSTs and sea ice + average 2081-2100 changes from 19 IPCC AR-4 models CHANGES IN SUMMER (JJA) MEAN DAILY MAX 8-HOUR OZONE 8