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 10, NUMBER 3, MARCH 1997
"Further Estimates of Radiative Forcing Due to Tropospheric Ozone
Changes," P.M. de F. Forster (Dept. Meteor., Univ. Reading, Reading RG6
6AU, UK; e-mail: email@example.com), C.E. Johnson et al., Geophys. Res.
Lett., 23(23), 3321-3324, Nov. 15, 1996.
Estimates made by two 2-D (latitude-height) chemical transport models show
large uncertainty, but continue to support the case that tropospheric ozone
changes make a substantial contribution (about 15%) to the total greenhouse gas
radiative forcing. Results also show that ignoring clouds and the effects of
stratospheric adjustment in the radiative forcing calculations overestimates the
global average forcing by about 66%.
"Climate Forcing by Stratospheric Ozone Depletion Calculated from
Observed Temperature Trends," W. Zhong (Dept. Phys., Imperial College,
London SW7 2BZ, UK), R. Tuomi, J.D. Haigh, ibid., 23(22),
3183-3186, Nov. 1, 1996.
Previous studies have concluded that ozone depletion leads to a net negative
radiative forcing, estimated by Ramaswamy et al. to be -0.08 W m-2 during the
period 1979-1990 (global-annual average). This effect has been considered
possible compensation for positive radiative forcing due to anthropogenic
greenhouse gases over the same period. More realistic radiation calculations
presented here show a much lower value of -0.025 W m-2, although inclusion of
some omitted factors would raise this value somewhat.
Special section: Clim. Change, 34(3-4), Nov.-Dec.
1996. Consists of three papers relating to global warming potentials: an
editorial comment on two-dimensional models and two papers that employ such
"Three-Dimensional Chemistry in the Greenhouse," D.J. Wuebbles
(Dept. Atmos. Sci., Univ. Illinois, 105 S. Gregory Ave., Urbana IL 61801),
397-404. Emphasizes that zonally-averaged, 2-D models of atmospheric chemistry
and transport processes, such as those used in the following two papers, can
provide important insights, but are inadequate for definitive evaluation of
tropospheric chemistry processes for a number of reasons that are discussed
"Estimates of Indirect Global Warming Potentials for CH4, CO and NOx,"
J.S. Fuglestvedt (Ctr. for Intl. Climate & Environ. Res. (CICERO), Univ.
Oslo, POB 1129 Blindern, N-0317 Oslo, Norway), I.S.A. Isaksen, W.-C. Wang,
"Relative Radiative Forcing Consequences of Global Emissions of
Hydrocarbons, Carbon Monoxide and NOx from Human Activities Estimated with a
Zonally-Averaged Two-Dimensional Model," C.E. Johnson (Meteor. Off., London
Rd., Bracknell, Berkshire RG12 2SY, UK), R.G. Derwent, 439-462.
"First Estimates of the Radiative Forcing of Aerosols Generated from
Biomass Burning Using Satellite Data," S.A. Christopher (Inst. Atmos. Sci.,
South Dakota Sch. of Mines & Technol., Rapid City SD 57701; e-mail: sundar@
cloud.ias.sdsmt.edu), D.V. Kilche et al., J. Geophys. Res., 101(D16),
21,265-21,273, Sep. 27, 1996.
Most previous studies have estimated the radiative impact of aerosols from
biomass burning by using some form of the radiative transfer equation. This
study measures the quantity using a combination of data from two satellite
instruments (AVHRR and ERBE), and finds net radiative forcing of about -36 W m-2
for areas with heavy aerosol loading, and about -16 W m-2 for optically thin
"Clouds and the Earth's Radiant Energy System (CERES): An Earth
Observing System Experiment," B.A. Wielicki (Atmos. Sci. Div., MS-420,
NASA-Langley Res. Ctr., Hampton VA 23681), B.R. Barkstrom et al., Bull.
Amer. Meteor. Soc., 77(5), 853-868, May 1996.
The CERES program will extend and improve on the Earth Radiation Budget
Experiment (ERBE) by flying broadband scanning radiometers on several NASA-EOS
satellites starting in 1998 and extending over at least 15 years. CERES will
also combine simultaneous cloud property data derived using EOS narrowband
imagers to provide a consistent set of cloud/radiation data at the surface and
at several selected levels of the atmosphere. [Technical details are available
Two items in Atmos. Environ., 30(10/11), May 1996:
"Radiative Forcing Due to Increased Tropospheric Ozone Concentrations,"
S. Chalita (Service d'Aéronomie du CNRS, Univ. Paris, 6 Pl. Jussieu,
Boite 102, 75252 Paris, Cedex 05, France), D.A. Hauglustaine et al., 1641-1646.
To determine their radiative forcing impact, pre-industrial and present-day
tropospheric ozone concentrations are simulated by a 3-D chemical transport
model in conjunction with a general circulation model. Ozone forcing is
regionally heterogeneous with a marked interhemispheric difference; it peaks
over the Northern Hemisphere continents in summer and locally reaches more than
1 W m-2. Changes in concentration in the high troposphere have about 10 times
more radiative impact than those in the planetary boundary layer. A 10% per
decade growth rate of ozone in the future implies an increase of 2 W m-2.
"The Role of Anthropogenic Emissions of NOx on Tropospheric Ozone over
the North Atlantic Ocean: A Three-Dimensional, Global Model Study," C.S.
D.D. Parrish (Aeron. Lab., NOAA, 325 Broadway, Boulder CO 80303) et al.,
1739-1749. The model is run with a baseline scenario and one in which North
American fossil fuel NOx emissions are reduced 50%. The NOx reduction produces a
30% reduction in the total mass of tropospheric ozone exported from North
America to the North Atlantic Ocean.
"The Greenhouse Earth: A View from Space," J.E. Harries
(Imperial College of Science, Blackett Lab., Imperial College, London SW7 2BZ,
UK), Quart. J. Royal Meteor. Soc., 122(532), 799-818, Apr. 1996
A review. Radiative cooling of the Earth in the absence of clouds has
recently been shown to be dominated by emission from water vapor in the upper
troposphere. The role of clouds is presently less clear, but in both cases, more
accurate global observations are needed. The paper is illustrated by data from
"Impacts of Increased Anthropogenic Emissions in Asia on
Tropospheric Ozone and Climate. A Global 3-D Model Study," T. Berntsen
(Inst. Geophys., Univ. Oslo, POB 1022, Blindern, 0315 Oslo, Norway), I.S.A.
Isaksen et al., Tellus, 48B(1), 13-32, Feb. 1996.
Asia was selected for study because its emissions are rapidly increasing,
and there is a large potential for future increases. A doubling of NOx emission
leads to ozone increases up to 30% in the upper troposphere. Increased
tropospheric ozone causes a positive radiative forcing of about 0.5 W m-2, which
is 30-50% of the estimated negative radiative forcing due to the direct effect
of sulfate aerosols.
"An Assessment of the Radiative Effects of Anthropogenic Sulfate,"
C.C. Chuang (Atmos. Sci. Div. L-103, Lawrence-Livermore Natl. Lab., POB 808,
Livermore CA 94550; e-mail: firstname.lastname@example.org), J.E. Penner et al., J.
Geophys. Res., 102(D3), 3761-3778, Feb. 20, 1997.
Uses a coupled climate-chemistry model with cloud nucleation processes to
investigate both direct and indirect sulfate radiative forcings. Estimates a
global direct radiative forcing of about -0.4 W m-2, with a maximum over Europe
where the strongest anthropogenic sulfur emissions occur. Different approaches
for estimating the indirect forcing yield a range of -0.6 to -1.6 W m-2.
Simulations indicate that anthropogenic sulfate may cause important increases in
reflected solar radiation, which would mask locally the warming from greenhouse
"Climate Implications of Biomass Burning Since the 19th Century in
Eastern North America," J.S. Clark (Dept. Botany, Duke Univ., Durham NC
27708), B.J. Stocks, P.J.H. Richard, Global Change Biology, 2(5),
433-442, Oct. 1996.
Recent predictions that tropospheric aerosols have counterbalanced
greenhouse warming assume aerosol emissions were low before 1850 and then
increased dramatically with industrialization of the Northern Hemisphere and
biomass burning in the tropics. This analysis of the lake sediment record of
emissions across North America indicates that aerosols could have actually decreased
during the 20th century, suggesting that the offset hypothesis requires further
analysis using different assumptions of past emissions. [The following entry
relates to this topic.]
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Index of Abbreviations