February 28, 2007
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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 8, NUMBER 10, OCTOBER 1995
EARTH RADIATION BUDGET
"The Effect of Clouds on Atmospheric Absorption of Solar Radiation,"
M.-D. Chou (NASA-Goddard, Greenbelt MD 20771), A. Arking et al., Geophys.
Res. Lett., 22(14), 1885-1888, July 15, 1995.
Clouds reduce atmospheric solar heating over wide ranges of solar zenith
angle, cloud height and surface albedo. For the ratio of cloud forcing at the
surface to that at the top of the atmosphere to reach 1.5, cloud-specific
absorption must increase by a factor of 40 beyond what has been measured by
aircraft. Since there are no observations to support such strong absorption, the
excess cloud absorption, if it occurs, must be explained by other factors.
"Changes in Surface Radiation Caused by a Scattering Layer as
Calculated Using Radiative Perturbation Theory," M.A. Box (School Phys.,
Univ. New South Wales, Sydney NSW 2052, Australia), J. Geophys. Res.,
100(D6), 11,581-11,584, June 20, 1995.
Computes changes in irradiance and actinic flux for wavelengths of 300 nm
and 550 nm with a range of layer elevations and solar zenith angles. Large
enhancements occur at 300 nm when both layer elevation and solar zenith angle
are high. At 550 nm, an unexpected enhancement is seen in actinic flux for small
solar zenith angles.
"First Global WCRP [World Climate Research Program] Shortwave
Surface Radiation Budget Dataset," C.H. Whitlock (Atmos. Sci. Div., MS 420,
Hampton VA 26381), T.P. Charlock et al., Bull. Amer. Meteor. Soc., 76(6),
905-922, June 1995.
Describes the first dataset of the project, and gives sample results for
several climate parameters, emphasizing their validation and limitations. For
most of the globe, satellite estimates have bias values between ±20 W m-2;
rms values are about 25 W m-2. There are regions with much larger uncertainties.
"The Albedo of Amazonian Forest and Ranch Land," A.D. Culf
(Inst. Hydrol., Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, UK), G.
Fisch, M.G. Hodnett, J. Clim., 8(6), 1544-1554, June 1995.
Presents long-term measurements of albedo at three paired sites in Brazil.
The mean forest albedo, 0.134, is slightly higher than the value generally used
in general circulation models. The mean ranch-land albedo, 0.180, is slightly
lower than the value usually used.
Two items in Geophys. Res. Lett., 22(8), Apr. 15, 1995:
"An Observation of the Greenhouse Radiation Associated with Carbon
Monoxide," W.F.J. Evans (Environ. Resour. Studies, Trent Univ.,
Peterborough ON K9J 7B8, Can.), E. Puckrin, 925-928. Uses ground-based
Fourier-transform infrared emission spectroscopy to show that carbon monoxide
may contribute directly to the radiation imbalance of the atmosphere. Accurate
measurements of thermal radiative flux from greenhouse gases for various
locations and seasons will help to develop our understanding of global warming
models and provide insight into future climatic changes.
"Effect of Absorbing Aerosols on Global Radiation Budget," P.
Chylek (Atmos. Sci. Prog., Dalhousie Univ., Halifax NS B3H 3J5, Can.), J. Wong,
929-931. Derives an expression for a globally averaged value of direct radiative
forcing by absorbing aerosols, and applies it to the case of aerosols produced
by biomass burning. Shows that direct radiative forcing is a sensitive function
of the size distribution of aerosol particles.
"Validation of Clear-Sky Fluxes for Tropical Oceans from the Earth
Radiation Budget Experiment [ERBE]," W.D. Collins (Scripps Inst. Oceanog.,
La Jolla CA 92093), A.K. Inamdar, J. Clim., 8(3), 569-578, Mar.
Confirms earlier work on the coupling between sea surface temperature and
the atmospheric greenhouse effect, in particular the existence of a super
greenhouse effect for oceans warmer than 300 K. The net bias introduced in the
monthly clear-sky fluxes is generally less than the systematic error in
estimates of the instantaneous fluxes. Comparison of general circulation models
and ERBE clear-sky longwave fluxes will probably depend explicitly on
"Radiation Budgets in the Western Tropical Pacific," M.-D. Chou
(Lab. Atmos., Code 913, NASA-Goddard, Greenbelt MD 20771), ibid., 7(12),
1958-1971, Dec. 1994.
Demonstrates the usefulness of ERBE radiances measured by satellites by
comparing the data with model calculations. The agreement indicates that
long-term earth radiation budgets in the area can be computed in this manner.
"The Chemical and Radiative Effects of the Mount Pinatubo Eruption,"
D.E. Kinnison (Lawrence-Livermore Natl. Lab., POB 808, Livermore CA 94550), K.E.
Grant et al., J. Geophys. Res., 99(D12), 25,705-25,731, Dec. 20,
Used a 2D, zonally averaged, chemical radiative transport model, integrated
with time from before the eruption through December 1993, to compare the effects
of heterogeneous chemical processing on sulfate aerosols with those of aerosol
heating (modifying either circulation or temperature). Compares various
scenarios with observations.
"Radiative Flux Opens New Window on Climate Research," R.T.
Pinker (Dept. Meteor., Univ. Maryland, College Pk. MD 20742), I. Laszlo et al.,
Eos, 76(15), 145, 155, Apr. 11, 1995.
Discusses how the combination of satellite observations and atmospheric
modeling has provided information on the radiative flux at the top and bottom of
the atmosphere, which has a variety of research uses for geophysicists,
agronomists, environmentalists and others.
"The Roles of Carbon Dioxide and Water Vapour in Warming and Cooling
the Earth's Troposphere," J. Barrett (Dept. Chem., Imperial Coll., S.
Kensington, London SW7 2AY, UK), Spectrochim. Acta, 51A(3),
415-417, Mar. 1995.
The widely held notion that rising levels of CO2 will lead to atmospheric
warming, and current global model simulations of that effect, depend on certain
assumptions. The atmosphere is assumed to behave as a continuous emitter of
broad spectrum cavity-type radiation as it re-emits the initially absorbed
terrestrial radiation, and vibrational fluorescence of CO2 is assumed to occur
substantially at all altitudes. This article presents evidence countering these
assumptions. See Res. News entry on "Cool Reception for Warming Predictions"
(J. Emsley, New Scientist, p. 19, Oct. 8, 1994), in Global Climate
Change Digest, Apr. 1995.
"Evidence of a Long-Term Increase in Tropospheric Ozone from Pic du
Midi Data Series: Consequences: Positive Radiative Forcing," A. Marenco
(Lab. d'Aérologie, CNRS-URA 0354, Univ. P. Sabatier, 31062 Toulouse
Cedex, France), H. Gouget et al., J. Geophys. Res., 99(D8),
16,617-16,632, Aug. 20, 1994.
Old ozone measurements recently discovered at the Pic du Midi Observatory
(altitude 3000 m, southwestern France) were used to complete a time series
covering 1874 to 1993. Ozone has increased by a factor of five since the
beginning of this century. For the first two decades of the period, the mixing
ratio was stable at 10 ppb, representing the preindustrial era. A tentative
evaluation of radiative forcing confirms that ozone is currently the second most
significant greenhouse gas, accounting for 22% of the radiative forcing changes
in the Northern Hemisphere since 1980.
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