Transcript 4. - UW Atmospheric Sciences

Half Earth, no title
Half Earth, title slide
I. Aerosol effects on climate:
A short history
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…
Photo credit: “The Blue Marble”
http://visibleearth.nasa.gov/view_rec.php?id=2429
1. The Climatic Role of Volcanism
Plutarch (44 B.C.)
Re: cooling caused by
Etna eruption
Franklin (1784)
Re: cool summer in Europe
caused by Laki eruption
Tambora Eruption (1815)
Caused “year without a
summer,” 1816, as far
away as New England
Humphreys (~1912)
Attempted quantification of
cooling from volcanic
aerosols
Mitchell (1961)
Volcanoes cause
interannual temperature
change
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
1. Role of Volcanism
Krakatoa, 1883
artist’s rendering
Krakatoa
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
2. Atmospheric Haze Optics
cai.blogware.com/_photos/Smog.jpg
Smog
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)
2. continued
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
3. Visibility
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)
4. Wartime & Cold War
Nephelometer
Nephelometer
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
4. Wartime, continued
Snorkel
Snorkel
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
5. Astro Approach
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
6. Tropospheric
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
6. Tropospheric, continued
6. Trop. “Background Aerosol” Effects, cont.
Junge (1975)
Suggested use of 2- or 3-D tropospheric source-transportremoval 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
6. Tropospheric, continued
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
7. Climatology
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
7. Climatology, cont.
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
8. Cloud Physics
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
8. Cloud Physics, cont.
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
9. Aerosol Sci & Atmos
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)
From Journal of the Air Pollution
Control Association, 1969
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)
9. Aerosol / Atmos, cont.
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
10. Chemically-identified
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)
11. Modeling
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
11. Modeling, cont.
12. Sulphate aerosol and climate, Nature, Vol. 348, p.
22
(1990).
R. J. Charlson
Department of
Atmospheric Sciences,
University of Washington, Seattle
J. Langner, H. Rodhe
Department of Meteorology,
Stockholm University,
Sweden
… A simple box-model calculation illustrates the expected
magnitude of the
BSO2–
mean column burden of anthropogenic sulphate,
:4
BSO2–
= 4
FSO2– SO2–
4
A
4
~
(3.3  106 g s-1)(5  105 s)
2.5  1014 m2
~ 6.6  10-3 g m-2)
FSO2
where – 4 is the average flux of this SO42– 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
4
6 days) and A is the area of the northern Hemisphere. We assume that all
anthropogenic SO 42– originates and stays in the Northern Hemisphere.
12. Simple Calculation
12. Sulphate aerosol and climate, Nature, Vol. 348, p.
22
(1990), cont.
An empirical optical scattering efficiency,  (10 m2 g-1, ref. 2), then
yields an estimate of optical depth SO2– , for solar wavelengths due to
4
anthropogenic SO 2– :
4
SO2– =
4

~
BSO2– 4
0.066
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):
L ~ (1 - f )  SO2– (2 SO2–) ~
4
4
0.8%
where the factor of two is the secant of solar zenith angle averaged over
the sunlit hemisphere…
12. Simple Calculation
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)
13. Aersol Sensing from Satellites
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
14. International Collab.
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
15. Political Recognition
15. Political Recognition of Climate Change
and Aerosols, cont.
Steven Schwartz (2007), personal communication
15. Political Recognition
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.
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.
II. Conclusions