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Half Earth, no title

Half Earth, no title. Robert J. Charlson Departments of Atmospheric Sciences and Chemistry University of Washington, Seattle. Or… An idiosyncratic view of how aerosol-climate research arrived at where it is today….

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Half Earth, no title

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  1. Half Earth, no title

  2. Robert J. Charlson Departments of Atmospheric Sciences and Chemistry University of Washington, Seattle Or…An idiosyncratic view of how aerosol-climate research arrived at where it is today… Or…An idiosyncratic view of how aerosol-climate research arrived at where it is today… Half Earth, title slide I. Aerosol effects on climate: A short history Photo credit: “The Blue Marble” http://visibleearth.nasa.gov/view_rec.php?id=2429

  3. 1. Role of Volcanism 1. The Climatic Role of Volcanism • Plutarch (44 B.C.)Re: cooling caused by Etna eruption • Tambora Eruption (1815)Caused “year without a summer,” 1816, as far away as New England • Mitchell (1961)Volcanoes cause interannual temperature change • Franklin (1784)Re: cool summer in Europe caused by Laki eruption • Humphreys (~1912)Attempted quantification of cooling from volcanic aerosols • Lamb (1970)Dust veil index • Minnis et al. (1993) Satellite (ERBE) observation of cooling of -1 to -2 W/m2 caused by Mt. Pinatubo, T~ -0.5C • Robock (1995)Review

  4. Krakatoa, 1883 artist’s rendering Krakatoa

  5. 2. Atmospheric Haze Optics 2. Atmospheric Haze Optics • Tyndall (1861) Particles scatter visible light • Ångström (1929) Defined atmospheric “turbidity” and its wavelength dependence • Volz (1956) Popularized measurement of turbidity • Flowers et al. (1969) Network of turbidity observations showed horizontal scale of ca. 1000 km

  6. cai.blogware.com/_photos/Smog.jpg Smog

  7. 2. continued 2. Atmospheric Haze Optics, cont. GMCC/CMDL (1976 – ), WMO-BSRN (early 1990s – ) Nephelometric and radiometric monitoring data in rural /remote locations Charlson and Pilat (1969) Aerosols can either heat or cool the Earth depending on light absorbing property Lin et al (1973) First filter data on light absorption by urban aerosols (Samples from NYC 1967)

  8. 3. Visibility 3. Visibility Koschmieder (1924) Theory of visual range Bergeron (1929) Observation in Sweden of long-range transport of visible hazes from the south Middleton (1952) Book: Vision Through the Atmosphere Rossano and Charlson (1965 – ca. 1972) Project: “Influence of aerosol characteristics on visibility” Duntley (1948 – ca. 1966) The Visibility Laboratory; Scripps Institution of Oceanography: Theory and observation of visibility in atmosphere and oceans

  9. 4. Wartime & Cold War 4. Wartime and ”Cold War ” Aerosol Research and High Level of Secrecy (1914 to mid 1960s) Waldram (1945) Measurement of optical transmission of atmosphere; both absorption and scattering (illuminated white target on ground with balloon-borne radiometer, at night) Beuttell and Brewer (1949) Integrating nephelometer development during WWII Green and Lane (1964) Described basic aerosol science needed by militaries (respirable chemical and biological agents; smoke screens for visibility degradation etc., from the U.K. Chemical Defence Experimental Establishment, Porton Down)

  10. Nephelometer Nephelometer

  11. 4. Wartime, continued 4. Wartime and ”Cold War" Aerosol Research, cont. Anonymous (1940s – 1950s) Use of GE condensation nucleus counter for tracking snorkeling submarines; declassified ca. 1964 Fuchs (1955) Soviet textbook on aerosol mechanics; classified version available to US military and US Public Health Service Fuchs (1964) Declassified book published in the West HASL (1940s until ca. 1965) High altitude sampling of radioactivity; discoveries of slow interhemispheric transport Ahlquist and Charlson (1967) UW obtains US patent on the high-sensitivity version of the integrating nephelometer

  12. Snorkel Snorkel

  13. 5. Astro Approach 5. Astronomical Approach; Solar Irradiance • Langley (1884)Method of estimating solar constant from flux at different air masses; yields both atmospheric optical depth and solar constant • Abbot (1911)Aerosol correction factor for determination of “solar constant” • Danjon (1928)Albedo of Earth via observation of the moon when illuminated by “Earthshine” • Hodge et al. (1968 – ca.1972)Project ASTRA, using observations with astronomical telescopes by NASA of star brightness to infer atmospheric aerosol optical depth • NASA Pioneer 5 (1959)Beginnings of satellite monitoring of solar flux; detailed solar flux record

  14. 6. Tropospheric “Background” 6. Tropospheric “Background Aerosol” Effects • Bryson (1967, 1974)Cooling due to anthropogenic changes in dust, e.g., from deserts • McCormick and Ludwig (1967)Increase in turbidity might be the cause of global cooling since the 1940s • Cobb (1970, 1973)No change in electrical conductivity of air over North Pacific and Southern Hemisphere; decrease over North Atlantic due to aerosol pollution • Mitchell (1970)Cooling from ca. 1940s to 1960s was an enigma and possibly part of a climatic “rhythm” • Mitchell in SCEP (1971)Lengthy discussion of heating versus cooling by anthropogenic aerosols

  15. 6. Tropospheric, continued 6. Trop. “Background Aerosol” Effects, cont. • Rasool and Schneider (1971)“An increase by only a factor of 4 in global aerosol background concentration may be sufficient to reduce the surface temperature by as much as 3.5° K”; suggested that this might “trigger an ice age” • Kellogg (various)Anthropogenic perturbation of “background aerosol”; used GNP as proxy for aerosol in global dispersion model

  16. 6. Tropospheric, continued 6. Trop. “Background Aerosol” Effects, cont. • Junge (1975)Suggested use of 2- or 3-D tropospheric source-transport-removal model; identified aerosol by region, not by chemical composition; defined background aerosol that fills “80% of the volume of the troposphere” • Robock (1978)Estimated the effect of anthropogenic aerosols by scaling to anthropogenic increase of CO2 • Coakley et al. (1983)“Background aerosol” cools Earth surface by 2 – 3° K

  17. 7. Climatology 7. Climatology; Indices of Climate Change • Avicenna (11th century) • Hotness and coldness measured by expansion of a gas • de Medici (1654) • Alcohol thermometer • Fahrenheit (1724) • Temperature scale • Celsius (1742) • 100 degree temperature scale based on freezing point and boiling point of water • Anon. (ca. 1850) • Beginnings of instrumental T record; T as index of climate

  18. 7. Climatology, cont. 7. Climatology; Indices of Climate Change, cont. • Keeling (1957, 1960) • Beginning and first data for continuous monitoring of CO2; change of CO2 as index of climate change; definition of T2x • Ramanathan (1980) • Concentrations of numerous GHG as indices of climate change (CO2, CH4, N2O etc.) • Dickinson and Cicerone (1986) • Magnitude of the imposed change in heat balance as index of climate change (W/m-2); emphasized that it was more certain than modeled temperature changes or forecasts • Charlson, Lovelock, Andreae, and Warren (1987) • CLAW hypothesis proposing a feedback of aerosol from marine dimethylsulfide on cloud albedo

  19. 8. Cloud Physics 8. Cloud Physics • Coulier (1875) and Aitken (1880) • Particles are necessary for formation of droplets in an expansion cloud chamber • Arrhenius (1896) • “Nebulosity” is a key factor in global heat balance • C. T. R. Wilson (1912) • Expansion cloud chamber; detection of subatomic particles • Köhler (1936 and earlier) • Theory: Water soluble particles act as cloud condensation nuclei (CCN); equation describing equilibrium cloud droplet size as a function of supersaturation

  20. 8. Cloud Physics, cont. 8. Cloud Physics, cont. • Junge (1975) • Differentiated between direct effect of aerosols on solar radiation and indirect effect of aerosol CCN on cloud albedo • Twomey (1971, 1977) • Theory of the effect of CCN on cloud albedo • Charlson et al. (1987) • Proposed that changes in emission of marine algal dimethylsulfide would influence cloud albedo

  21. 9. Aerosol Sci & Atmos Chem 9. Aerosol Science and Atmospheric Chemistry • World War I • British physicochemist F. G. Donnan coined term “aerosol”, meaning particles suspended in a gaseous medium; analogous to “hydrosol” • 1940s until mid 1960s • Stratospheric sampling of radioactive bomb debris • Junge (1962) • Summarized measurements of aerosol properties and size distributions in book “Air Chemistry and Radioactivity” • Bullrich (1964) • Book describing aerosol effects on atmospheric radiative transfer; largely the results of post WWII research on atmospheric optics/radiative transfer in Germany sponsored by US Air Force

  22. From Journal of the Air Pollution Control Association, 1969 9. Aerosol / Atmos, cont. 9. Aerosol Sci. and Atmospheric Chem., cont. • Whitby and Clark (1966) • Electronic method for measuring “complete” size distribution based on ion mobility • Whitby et al. (1972) and Husar et al. (1972) • First measurements and dynamical explanation of bimodal size distribution of Los Angeles smog • Charlson et al. and Waggoner et al. (1967-1976) • Summarized light scattering efficiency of tropospheric aerosols • (ca. 3 m2/g for sub m or “accumulation mode” aerosol)

  23. 9. Aerosol / Atmos, cont. 9. Aerosol Sci. and Atmospheric Chem., cont. • Covert et al. (1974) • Measurement of the increase in aerosol scattering caused by increased RH, utilizing a (then) modern version of the Beuttell & Brewer nephelometer. • Waggoner et al. (1976) • Sulfate-light scattering ratio; empirical observations from aircraft of scattering efficiency by sulfates: (5 m2/g dry; 8.5m2/g at average PBL RH)

  24. 10. Chemically-identified 10. Chemically-Identified Anthropogenic Aerosol • Date? • Chemical mechanism; SO2 as source of SO4 = aerosol via gas-to-particle conversion • Bolin and Charlson (1976) • Loss of solar radiation and cooling in industrial regions due to • anthropogenic sulfate aerosol; predicted temperature decrease in industrial regions; missed the connection to regional sulfur mass balance • Charlson, Langner and Rodhe (1990, 1991) • Radiative forcing of climate by anthropogenic sulfate, global mean • ca. -0.6 W/m2(hereafter “climate forcing”) • Penner and Dickinson (1992) • Forcing by smoke from biomass combustion • Charlson et al. (1992) • Review of climate forcing by anthropogenic aerosol; • emphasized the need for “separation of the forcing by anthropogenic sulfate aerosol from…” the total

  25. 11. Modeling 11. Modeling • Arrhenius (1896) • Simple equilibrium model of incoming solar radiation and outgoing longwave radiation; included “nebulosity” due to clouds as an influence on albedo • Plass (1961) • Equilibrium surface temperature as f (CO2) • Manabe and Wetherald (1967) • 1-D radiative convective model, no aerosols • Rasool and Schneider (1971) • 1-D planetary radiation model with aerosols and fixed clouds • Budyko (1969) • Climatic effect of loss of solar radiation (Tellus) • Manabe and Wetherald (1975) • 3-D radiative-convective model with fixed clouds and no aerosol • Granat, Rodhe, and Hallberg (1976) • Global sulfur budget of the atmosphere (SCOPE 7)

  26. 11. Modeling, cont. 11. Modeling, cont. • Isaksen and Rodhe(1980) • 2-D model of atmospheric sulphur, including sulfate aerosols • Zimmerman (1987) • 3-D model of cycling of atmospheric tracers (MOGUNTIA) • Langner and Rodhe (1991) • 3-D model of atmospheric sulfur, using MOGUNTIA • Charlson, Langner and Rodhe (1990, 1991) • Climate forcing by anthropogenic sulfate aerosols; utilized a 0-D and then a 3-D mass balance model of anthropogenic sulfur (MOGUNTIA) plus empirical scattering efficiency and angular scattering information • Knutti and others (early 2000s) • Inverse calculation using a climate model and known/assumed sensitivity to yield aerosol climate forcing • Anderson et al. (2003) • Inverse calculation of aerosol forcing yields a narrower range of possible forcings and smaller magnitude forcings than forward calculations

  27. R. J. Charlson Department of Atmospheric Sciences, University of Washington, Seattle J. Langner, H. Rodhe Department of Meteorology, Stockholm University, Sweden FSO2–SO2– 4 4 (3.3  106 g s-1) (5  105 s) BSO2–: 4 ~ BSO2–= A 4 2.5  1014 m2 ~ 6.6  10-3 g m-2) FSO2– 4 where is the average flux of this SO 2– through the atmosphere in the Northern Hemisphere (equivalent to about half of 70 Tg yr -1 of sulphur emitted as SO2);  SO2– is the mean sulphate aerosol particle lifetime (about 6 days) and A is the area of the northern Hemisphere. We assume that all anthropogenic SO 2– originates and stays in the Northern Hemisphere. 4 4 4 12. Simple Calculation 12. Sulphate aerosol and climate, Nature, Vol. 348, p. 22 (1990). … A simple box-model calculation illustrates the expected magnitude of the mean column burden of anthropogenic sulphate,

  28. An empirical optical scattering efficiency,  (10 m2 g-1, ref. 2), then yields an estimate of optical depth SO2– , for solar wavelengths due to anthropogenic SO 2– : 4 4  BSO2– 4 ~ 0.066 SO2–= 4 L ~ (1 - f )  SO2– (2 SO2–) ~ 0.8% 4 4 12. Simple Calculation 12. Sulphate aerosol and climate, Nature, Vol. 348, p. 22 (1990), cont. Finally, an empirical backscatter fraction,  (0.15, ref. 3), and estimated cloud fraction, f (~0.6), allow for estimation of the energy lost from the Earth’s surface, L (we disregard the effect of aerosols above cloudy areas): where the factor of two is the secant of solar zenith angle averaged over the sunlit hemisphere…

  29. 13. Aersol Sensing from Satellites 13. Aerosol Sensing from Satellites (Examples) • Stowe, Durkee et al. (1978 – )Advanced Very High Resolution Radiometer (AVHRR); aerosol optical depth (inverse method) • McCormick et al. (1979 – ) • Stratospheric Aerosol and Gas Experiment (SAGE); limb scanner; volcanic plumes • Cess, Ramanathan et al. (1984 – ?) • Earth Radiation Budget Satellite (ERBS); ERBE on NOAA 9, 10; scanning multi-band radiometer (broadband) • McCormick et al. (1994) • Lidar In-Space Technology Experiment (LITE) aboard Shuttle • Wielicki et al. (1997, 1999 – ) • Clouds and the Earth’s Radiant Energy System (CERES); based on successful ERBE instrument • French Space Agency (1996-7, 2002-3, – ) • Polarization and Directionality of the Earth’s Reflectances (POLDER) • Winker et al. (2006 – ) • Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Obseration (CALIPSO)

  30. 14. International Collab. 14. International Collaborative Reviews That Included Aerosol Effects on Climate • Matthews et al. (1971) • Study of Critical Environmental Problems (SCEP) • SMIC (1971) • Inadvertent Climate Modification • GARP (1975) • The Physical Basis of Climate and Climate Modeling (GARP 16) • SCOPE (1971-1986…) • Several books on biogeochemical cycles

  31. 15. Political Recognition 15. Political Recognition of Climate Change and Aerosols • Revelle et al., in White House conference on the environment (1965) • Anthropogenic CO2 increase amounts to an unplanned and unpredictable “vast geophysical experiment” • Dubridge (1970) • “If we were clever enough to balance these two effects – the reflectivity of particulate matter and the concentration of carbon dioxide – the Earth's temperature might stay constant.” (U.S. News and World Report, Jan. 1970) • US NRC (1991) • Discussed the possibility of adding aerosols to cancel out GHG effects • J. Climatic Change (2006) • Special issue on geoengineering with articles by Cicerone, Crutzen, and others; “Geoengineering” by adding aerosols to the stratosphere might be necessary • IPCC (1990, 1992, 1995, 2001, 2007) • Aerosols included as climate forcing agents first in 1992, introduced to IPCC by Rodhe and Watson

  32. 15. Political Recognition 15. Political Recognition of Climate Change and Aerosols, cont. Steven Schwartz (2007), personal communication

  33. II. Conclusions II. Conclusions 1. Many areas of scientific endeavor have contributed to current knowledge of aerosol effects, from astronomy to geology and atmospheric chemistry. 2. Many of these areas are isolated from one another and interchange has been slow and dependent upon random efforts by individuals. 3. All of the necessary information to calculate global climate forcing by anthropogenic sulfates was available by ca. 1976, but the key to doing it appeared to be the emphasis of forcing as an index of climate change rather than temperature.

  34. II. Conclusions II. Conclusions, cont. 4. Projecting to the future, the need for faster/more certain progress would seem to require interdisciplinary coordination as well as accurately posing the scientific questions re: what we do not yet understand and cannot yet measure with sufficient accuracy. 5. International coordination is needed. 6. Example of a large uncertainty that presently impedes progress: Measurement of global albedo and sensitivity of albedo to perturbations from either climate change or aerosols.

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