Interconnections between Air Pollution, Climate Change and Health

Transcription

1 Interconnections between Air Pollution, Climate Change and Health Denise Mauzerall Princeton University National Academies Institute of Medicine San Francisco, CA September 10, 2007

2 Air Pollution Adversely Impacts Health The World Health Organization identified ambient air pollution as a high public health priority, based on estimates of air pollution related death and disability-adjusted life years derived in its Global Burden of Disease initiative Particulate matter (PM) and ozone (O 3 ) exposure lead to adverse health effects for which concentration:response relationships have been established. Ozone is associated with premature mortalities and respiratory ailments. (Bell et al., JAMA, 2004, Epidemiology, 2005; Levy et al., Epidemiology, 2005; Ito et al., Epidemiology, 2005). Both long and short-term exposure to PM can result in premature mortality and cardio pulmonary disease. (Dockery et al., New England Journal of Medicine, 1993; Pope et al., JAMA, 2002; Laden et al., Am J Respir Crit Care Med, 2006)

3 Air Pollution and Climate Change are Interconnected Air pollutants and GHG are often emitted by the same sources. Hence changes in these activities can effect both types of emissions Some air pollutants increase radiative forcing (eg. ozone, black carbon (soot)); others decrease it (eg. sulfate and organic aerosols). Higher temperatures increase ozone concentrations through increases in chemical reaction rates and increases in biogenic emissions of hydrocarbons which are precursors of ozone Tropospheric ozone (O 3 ) is a critical link between air pollution and climate change. Ozone is a GHG. Ozone is a precursor for OH which removes air pollutants and reactive GHG from the atmosphere. Ozone is also a criteria air pollutant with adverse effects on health and ecosystems.

4 Radiative Forcing of Climate, 1750-Present Important Contributions of Air Pollutants IPCC, 2007

5 Tropospheric O 3 and Aerosols versus Well-mixed Greenhouse Gases (WMGG) Characteristic Tropospheric O 3 & Aerosols WMGG Atmospheric Concentration Depends on precursor emissions, chemistry, transport and deposition Determined primarily by direct emissions Distribution Variable in space and time Approximately homogenous Lifetime Weeks Years to decades Radiative forcing (RF) Other Effects Depends on vertical and horizontal distribution. Some have positive, others negative RF Adverse impacts on human health and ecosystems Relatively uniform and positive Small contribution of CH 4 to O 3 concentrations

6 Climate Warming is Likely to Increase Regional Air Pollution Episodes in the US Severity and duration of summer regional pollution episodes in the mid-west and northeastern US are predicted to increase in 2050 relative to present. Pollution episodes are more effected by climate change than mean values. Pollutant concentrations during episodes are predicted to increase 5-10%. Mechanism: increased stagnation in a warmer climate resulting from reduced ventilation of surface air from convection and frontal passages. With predicted climate change by 2050, additional emission controls are needed to meet a given ozone air quality target. Mickley et al., Geophys. Res. Lett., 2004; Wu et al. JGR, in press 2007

7 Linkages between Emission Sources and Control Options End-of-pipe controls can reduce emissions of reactive air pollutants that directly harm health, but these controls require energy and hence increase CO 2 emissions. Increases in efficiency reduce emissions of both reactive air pollutants and CO 2. Some energy technologies permit simultaneous reductions in emissions of air pollutants and GHG (eg. wind or solar power substituting for coal reduces emissions of CO 2, SO 2, Hg, NO x ), advanced coal gasification technology (eg. IGCC) allows separation of air pollutants and sequestration of CO 2.

8 Co-Benefits Concept Opportunities exist to simultaneously improve air quality and reduce radiative forcing. The main GHG and the main air pollutants largely come from the same sources. Reductions in some air pollutants reduce radiative forcing (eg. BC, CO, VOCs) Reductions in some GHG (eg. CH 4 ) reduce air pollutants and associated health impacts globally (eg. O 3 ).

9 It s Not Just about Climate Change: How Reducing Methane Emissions Can Improve Air Quality and Global Public Health Jason West, Arlene Fiore, Larry Horowitz & Denise Mauzerall Global Health Benefits of Mitigating Ozone Pollution with Methane e Emission Controls, Proceedings of the National Academy of Science, vol. 103, no. 11, pp , March 14, 2006

10 Tools Use MOZART-2 - Global 3-D Atmospheric Chemistry Transport Model to simulate global chemical distributions Model includes: chemical emissions, chemical reactions, chemical transport, winds, convection, solar radiation, surface deposition. Model evaluated with surface, sonde and aircraft data. Use GFDL Radiative Transfer Model to simulate radiative fluxes for MOZART-2 simulated chemical distributions Graedel and Crutzen, 1997

11 Methane Emissions Affect Ozone Air Quality as well as Climate Methane contributes to the formation of ozone, a primary component of photochemical smog. VOCs + NO x + sunlight O 3 Ozone is associated with premature mortalities (Bell et al., 2004, 2005; Levy et al., 2005; Ito et al., 2005). Background concentrations of ozone are increasing globally due in part to increasing methane.

12 Background Ozone is Growing and Will Continue to Grow! Historic and future increases in background ozone are due mainly to increased methane and NO X emissions (Wang et al., 1998; Prather et al., 2003) (IPCC A2) Ozone trend at European mountain sites, (Marenco et al., 1994).

13 Can methane emission reductions be justified for ozone air quality purposes? Objectives: 1) Estimate the global benefits to human health (lives saved) by controlling methane emissions and hence reducing background O 3 concentrations. 2) Compare the global health benefits with the costs of controlling methane.

14 Global Methane Emissions Natural: 180 Mton CH 4 yr -1 Termites Ocean Coal Oil Gas Biofuel Wetlands Rice Other Wastewater Landfills Biomass burning Animals Anthropogenic: 300 Mton CH 4 yr -1 * USA is ~9% of global anthropogenic emissions. EDGAR3.2 & Houweling et al., 1999

15 How Much Can Methane Be Reduced? West & Fiore (2005) Methane reduction potential from IEA (2003), for coal, oil and gas operations, wastewater, and landfills; maximum technically feasible in Comparison: Clean Air Interstate Rule reduces O ppb over the eastern US, at $0.88 billion yr -1, through NO X control.

16 A 20% decrease in global anthropogenic methane emissions decreases ozone globally by ~1 ppb. Change in annual average 8-hr. ozone

17 Avoided Premature Mortalities in 2030 from a 20% reduction in CH 4 emissions A 65 Mton yr -1 decrease (~20%) in methane emissions will prevent ~30,000 premature mortalities in 2030 (~0.04% of total deaths), and ~370,000 from

18 Multiple Benefits of Reducing Methane Reducing ~20% of anthropogenic methane emissions will: Be possible at a net cost-savings. Reduce 8-hr. average ozone globally by ~1 ppb. Reduce global radiative forcing by ~0.14 W m -2. Provide ~2% of global natural gas production. Prevent ~30,000 premature deaths globally in 2030, ~370,000 from

19 Double dividend of methane emission controls: - Decreased greenhouse warming - Improved air quality everywhere US ozone concentration Standard Local Regional Background Historical Future Continued domestic emission controls Opportunity for global methane controls Methane abatement can be a cost-effective component of international long-term ozone management.

20 Reductions in which O 3 precursor emissions are most effective at simultaneously reducing radiative forcing and surface O 3 concentrations? Goal: Determine which emission reductions lead to the greatest reduction in radiative forcing per unit reduction in surface O 3. West, J.J., A.M. Fiore, V. Naik, L.W. Horowitz, M.D. Schwarzkopf,, D.L. Mauzerall, Ozone Air Quality and Radiative Forcing - Consequences of Changes in Ozone Precursor Emissions, Geophys. Res. Lett., 34, 2007.

21 Radiative Forcing of Climate, 1750-Present Important Contributions from Ozone and Methane

22 Ozone Precursors Affect Both Ozone Air Quality and Climate Forcing Urban Global hν hν O 3 O 3 NO NO 2 NO NO 2 HO 2 OH HO 2 OH NMVOCs, CO NMVOCs, CO, CH 4

23 Ozone Precursors Affect Both Ozone Air Quality and Climate Forcing Global rapid local decadal global hν NO NO 2 O 3 NO X O 3 OH CH 4 O 3 HO 2 OH VOCs, CO O 3 NMVOCs, CO, CH 4 OH CH 4 O 3 decadal global CH 4 O 3 OH CH 4 O 3

24 Objectives 1) Estimate the consequences of 20% reductions in emissions of ozone precursors: NO x, NMVOCs, CO, CH 4 on - surface ozone ( O 3 srf ) and - net radiative forcing ( RF net ). 2) Consider the climate forcing implications of actions to improve ozone air quality, by estimating the change in net radiative forcing per unit change in surface ozone ( RF net / O 3 srf ).

25 Effect of global 20% anthropogenic emission reductions on 8-hr daily maximum surface O, averaged over 3 month period with highest O, at steady state. Surface ozone changes due to 20% reduction in anthropogenic emissions

26 RF net / O srf 3 Effects of 20% reductions in anthropogenic emissions RF net O 3 srf global populationweighted 8hr. 3-month average 0.04 NOX NMVOC CO CH4 0 NOX NMVOC CO CH W m ppbv METHANE OZONE RF net / O 3 srf W m -2 ppbv NOX NMVOC CO CH4 Reducing methane emissions causes the greatest reduction in RF per unit improvement in O 3 air quality.

27 Conclusions Based on 20% reductions of anthropogenic emissions: NO x reductions best decrease population-weighted O 3 srf. CH 4 reductions best decrease global annual O 3 srf. CH 4 reductions best decrease RF net (NO x reductions slightly increase RF net ). Of the means to improve ozone air quality, CH 4 emission reductions best decrease climate forcing per unit reduction in surface ozone ( RF net / O 3 srf ). CH 4 is followed by CO, NMVOCs, and NO x Because of long-term reductions in both radiative forcing and surface ozone concentrations, increased effort to reduce CH 4 emissions and increased emphasis on CO and NMVOC abatement is justified.

28 Summary Higher temperatures and changing meteorology from climate change will likely worsen air pollution episodes in the eastern and mid-western US given constant emissions. Our research shows that opportunities exist to simultaneously improve ozone air quality globally (and hence health) and reduce radiative forcing by reducing emissions of methane, CO and NMVOCs. Certain energy technologies (eg. renewables, advanced coal gasification technology, improved efficiency, etc.) can simultaneously reduce emissions of GHG and air pollutants which directly damage health.

29 More information about our work is available at: