* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download PPT
Climate change denial wikipedia , lookup
Soon and Baliunas controversy wikipedia , lookup
Atmospheric model wikipedia , lookup
Citizens' Climate Lobby wikipedia , lookup
Mitigation of global warming in Australia wikipedia , lookup
Climate change adaptation wikipedia , lookup
Climate engineering wikipedia , lookup
Climate change in Tuvalu wikipedia , lookup
Climate governance wikipedia , lookup
Economics of global warming wikipedia , lookup
Intergovernmental Panel on Climate Change wikipedia , lookup
Climatic Research Unit documents wikipedia , lookup
Climate change and agriculture wikipedia , lookup
Climate change and poverty wikipedia , lookup
Global warming controversy wikipedia , lookup
Media coverage of global warming wikipedia , lookup
Effects of global warming on humans wikipedia , lookup
Climate change in the United States wikipedia , lookup
Criticism of the IPCC Fourth Assessment Report wikipedia , lookup
Clean Air Act (United States) wikipedia , lookup
Global Energy and Water Cycle Experiment wikipedia , lookup
Effects of global warming on Australia wikipedia , lookup
Scientific opinion on climate change wikipedia , lookup
Physical impacts of climate change wikipedia , lookup
Fred Singer wikipedia , lookup
Surveys of scientists' views on climate change wikipedia , lookup
Global warming hiatus wikipedia , lookup
Instrumental temperature record wikipedia , lookup
Years of Living Dangerously wikipedia , lookup
Climate sensitivity wikipedia , lookup
General circulation model wikipedia , lookup
Politics of global warming wikipedia , lookup
Global warming wikipedia , lookup
Solar radiation management wikipedia , lookup
Attribution of recent climate change wikipedia , lookup
Climate change feedback wikipedia , lookup
Climate change, industry and society wikipedia , lookup
TROPOSPHERIC OZONE AS A CLIMATE GAS AND AIR POLLUTANT: THE CASE FOR CONTROLLING METHANE Daniel J. Jacob with Loretta J. Mickley, Arlene M. Fiore, Yaping Xiao MILLENIAL TEMPERATURE TREND [Mann et al., 1999; adopted by IPCC 2001] RADIATIVE FORCING AS INDEX OF CLIMATE FORCING Climate models (GCMs) indicate DTsurface = l DF where l (climate sensitivity parameter) ranges from 0.3 to 1.4 K m2 W-1 depending on the GCM RADIATIVE FORCING OF CLIMATE, 1750-PRESENT IPCC [2001] “Kyoto also failed to address two major pollutants that have an impact on warming: black soot and tropospheric ozone. Both are proven health hazards. Reducing both would not only address climate change, but also dramatically improve people's health.” (George W. Bush, June 11 2001 Rose Garden speech) TROPOSPHERIC vs. STRATOSPHERIC OZONE NOx = NO + NO2: nitrogen oxide radicals VOC (volatile organic compounds) = light hydrocarbons and substituted organic compounds TERRESTRIAL RADIATION OBSERVED FROM SPACE Scene over Niger Valley, northern Africa Ozone absorption feature at 9.6 mm; pressure-broadened in troposphere Ozone also has “shortwave forcing” by absorption of solar UV radiation GLOBAL BUDGET OF TROPOSPHERIC OZONE Tropospheric ozone is the primary source of OH, the main atmospheric oxidant Global sources and sinks, Tg O3 yr-1 (GEOS-CHEM model) O2 hn O3 STRATOSPHERE 8-18 km Chem prod in troposphere 4900 Chem loss in troposphere 4200 Transport from stratosphere 500 Deposition 1200 TROPOSPHERE hn O3 Deposition NO2 NO OH HO2 hn, H2O Pacman of the atmosphere! CO, CH4, VOC Main sink for CH4 H2O2 NOx EMISSIONS (Tg N yr-1) TO THE TROPOSPHERE NOx is the limiting precursor for tropospheric ozone formation LIGHTNING 5.8 STRATOSPHERE 0.2 SOILS 5.1 BIOMASS BURNING BIOFUEL 5.2 AIRCRAFT 2.2 0.5 FOSSIL FUEL 23.1 GLOBAL DISTRIBUTION OF TROPOSPHERIC OZONE Lifetime is < 1 wk in surface air, several wks in free troposphere Climatology of observed ozone at 400 hPa in July from ozonesondes and MOZAIC aircraft (circles) and corresponding GEOSCHEM model results for 1997 (contours). GEOS-CHEM tropospheric ozone columns for July 1997 Li et al. [2001] CURRENT GENERATION OF OZONE MODELS (IPCC) UNDERESTIMATES OZONE RISE IN 20th CENTURY Preindustrial ozone models } Observations at mountain sites in Europe [Marenco et al., 1994] RADIATIVE FORCING BY TROPOSPHERIC OZONE COULD THUS BE MUCH LARGER THAN IPCC VALUE Global simulation of late 19th century ozone observations with the GISS GCM Standard model: DF = 0.44 W m-2 “Adjusted” model (lightning and soil NOx decreased, biogenic hydrocarbons increased): DF = 0.80 W m-2 [Mickley et al., 2001] RADIATIVE FORCING FROM TROPOSPHERIC OZONE Annual mean values: note heterogeneity Mickley et al. [1999] DF = 0.46 W m-2 How good is radiative forcing as an indicator of climate change, when forcing is so heterogeneous? GISS GCM ANALYSIS OF CLIMATIC RESPONSE TO TROPOSPHERIC OZONE CHANGE OVER 20th CENTURY GCM equilibrium simulation for present-day climate with present vs. preindustrial tropospheric ozone; sea surface temperatures allowed to respond equilibrium climate present-day ozone Preindustrial ozone DF = 0.46 W m-2 DT = 0.3oC L.J. Mickley, Harvard INHOMOGENEITY OF CLIMATE RESPONSE TO OZONE CHANGE OVER 20th CENTURY • Greater warming in northern hemisphere (due to more ozone and albedo feedback in Arctic) •Strong cooling in stratosphere: Stratospheric ozone Tropospheric ozone 9.6 mm L.J. Mickley, Harvard Surface CLIMATE RESPONSE EXPERIMENTS WITH IDENTICAL GLOBAL RADIATIVE FORCINGS (0.46 W m-2) FROM: 1. 2. 3. Tropospheric ozone Uniform tropospheric ozone (18 ppv) Carbon dioxide (25 ppmv) • CO2 is a more effective warming agent at surface • In lower stratosphere, CO2 causes warming while tropospheric ozone causes cooling L.J. Mickley, Harvard LOWER STRATOSPHERIC COOLING FROM TROPOSPHERIC OZONE IS STRONGEST IN ARCTIC WINTER particularly sensitive region for recovery of ozone layer! GCM temperature change in lower stratosphere in DJF (oC) from increasing tropospheric ozone over 20th century L.J. Mickley, Harvard WHY IS CO2 MORE EFFECTIVE THAN OZONE FOR SURFACE WARMING AT SAME RADIATIVE FORCING? Correlation of forcing with 500 hPa humidity in tropics (25N-25S) Ozone CO2 DFCO2 – DFO3 Overlap of CO2 and H2O bands causes CO2 forcing to shift poleward where ice feedback enhances warming L.J. Mickley, Harvard GCM SURFACE WARMING PATTERNS (oC) FROM INCREASING TROPOSPHERIC OZONE OVER 20th CENTURY – JJA SURFACE Tropospheric ozone Equivalent uniform CO2 Difference (white = insignificant or high altitude) Largest warmings downwind of ozone source regions L.J. Mickley, Harvard SURFACE OZONE IS THE #1 AIR POLLUTANT IN U.S. Mean # summer days (1980-1998) exceeding U.S. ozone air quality standard (84 ppbv, 8-hour average) EPA/AIRS data [Lin et al., 2001] ANTHROPOGENIC ENHANCEMENT OF TROPOSPHERIC OZONE BACKGROUND IS A SIZABLE INCREMENT TOWARDS VIOLATION OF U.S. AIR QUALITY STANDARDS (even more so for European standards!) Europe (8-h avg.) Europe (seasonal) 0 preindustrial 20 40 present background U.S. (8-h avg.) 60 80 U.S. (1-h avg.) 100 120 ppbv SUMMER 1995 MEAN AFTERNOON OZONE IN SURFACE AIR Fiore et al. [2002] AIRS observations GEOS-CHEM model (r2 = 0.4, bias=3 ppbv) “Background ozone” produced outside the North American boundary layer contributes 15-35 ppbv to mean surface air concentrations in the model Combined effects of future anthropogenic emission trends on U.S. ozone air quality and on global climate Ozone pollution IPCC scenario Fossil fuel NOx emissions (2020 vs. present) Global U.S. Methane concentration (2020 vs. present) A1 +80% -30% +35% B1 +10% -60% +20% Fiore et al. [2002] HISTORICAL METHANE TRENDS AND IPCC PROJECTIONS Recent methane trend Historical methane trend IPCC projections All IPCC scenarios project increases in CH4 emissions over next 50 years – but can we try to decrease CH4 instead? PRESENT-DAY EMISSIONS OF METHANE: ASIA IS A MAJOR SOURCE REGION Y. Xiao, Harvard QUANTIFYING ASIAN SOURCES OF METHANE USING AIRCRAFT OBSERVATIONS OF ASIAN OUTFLOW NASA/TRACE-P mission, Feb-Apr 2001 TESTING a priori ASIAN METHANE SOURCE ESTIMATES WITH TRACE-P CORRELATIONS FOR CH4-C2H6-CO Y. Xiao, Harvard GEOS-CHEM vs. observed CH4: a priori Asian CH4 source too high by 25% GEOS-CHEM vs. observed C2H6/CH4: Coal mining CH4source likely too high