February 28, 2007
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A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 11, NUMBER 9, SEPTEMBER 1998
OF GENERAL INTEREST
Contribution of Hurricanes to Local and Global Estimates of Air-sea
Exchange of CO2, N. R. Bates, A. H. Knap, and A. F.
Michaels, Nature 395, 58-61 (Sept. 3, 1998).
The Sargasso Sea was sampled before and after hurricane Felix in 1995.
Measurements of surface seawater temperature showed a cooling of about 4°C
that lasted 2 to 3 weeks. At the same time, the seawater partial pressure
of CO2 decreased by almost 60 matm. From these figures, an
increase of almost 55% was estimated in the summertime efflux of CO2
into the atmosphere over this part of the Sargasso Sea. Extrapolating this
rate to all hurricanes led to an estimate that those storms contribute
0.04 to 0.51 Pg C to the atmosphere per year. Such effluxes would exert an
important influence on ocean-atmosphere CO2 exchange and on
the annual variability of CO2 fluxes over the subtropical
Global Variations in Droughts and Floods: 1900-1995, A. Dai,
K. E. Trenberth, and T. R. Karl,Geophysical Research Letters 25
(17), 3367-3370 (Sept. 1, 1998).
Regions of the Earth experiencing unusually wet or dry conditions have
increased during the past 30 years. The overall trend is small. Increases
were found in drought-affected areas in Africa and Asia and in both
extremely wet and extremely dry areas in Europe and the United States.
These changes were particularly noticeable in regions affected by El Niño.
These findings are in accord with predictions of climate researchers, who
say that global warming could promote drought in some areas and extreme
wetness in others.
Key Issues in Global Change, K. Y. Kondratyev
(email@example.com),Tiempo No. 28,
(June 1998); this article also appeared as Key Issues of Global
Change at the End of the Second Millennium, European Geophysical
Society Newsletter No. 63 (June 1997).
Kondratyev lays out five principles that, he believes, should underlie
all global-change research: (1) The Earth is a unique planet in the solar
system in that life exists on it in the form of biota. (2) Homo
sapiens is one of the species of the biota; if that species
principal aim were not to support the global biosphere, it would be
impossible to develop sustainment. (3) Simple approximations indicate that
a stable biosphere can be guaranteed only if not more than 1% of the
biospheric resources are used; at present, this number is close to 10%.
(4) Parity in the use of existing resources by the developed and the
developing countries must be established through relevant international
agreements. (5) More efforts are necessary to develop clean and efficient
technologies, minimize the use of energy and raw materials, and reduce the
A Neoproterozoic Snowball Earth, P. F. Hoffman
(firstname.lastname@example.org), G. P. Halverson, and D. P. Schrag, Science
281, 1342-1346 (Aug. 28, 1998).
Studies of carbon-isotope anomalies in Neoproterozoic carbonate rocks in
glacial deposits in Namibia were combined with estimates of thermal
subsidence history. The results suggested a multimillion-year-long
collapse of biological productivity in the surface ocean. An explanation
of such a collapse is proffered in the form of a global glaciation (i.e.,
a snowball Earth). The postulated snowball is expected to have ended
relatively abruptly under the influence of a massive greenhouse effect
produced by atmospheric carbon dioxide concentrations about 350 times
those seen today. Such CO2 levels are attributed to volcanic
outgassing. These high CO2 concentrations are expected to have
rapidly warmed the Earth to extreme greenhouse conditions. Absorption of
the atmospheric carbon dioxide by the ocean would then have resulted in
the rapid precipitation of calcium carbonate producing the cap carbonate
rocks that are observed globally today.
Asynchrony of Antarctic and Greenland Climate Change During the Last
Glacial Period, T. Blunier et al., Nature 394,
739-743 (Aug. 20, 1998).
Rapid temperature oscillations of about 15° C called Dansgaard-Oeschger
events occurred in Greenland about every 3000 years during the last
glaciation. Examination of the Antarctic temperature record for the same
general period indicates analogous warming/ cooling events. Ice cores from
central Greenland (GRIP) and west Antarctica (Byrd) were compared in
detail to determine whether these temperature variations occurred
simultaneously in the two hemispheres or led in one hemisphere or the
other. Variation in the isotopic distribution of oxygen in the ice cores
was used to determine the temperature records for each site. Correlation
of the cores from the two sites was made possible by maintaining
consistency between their respective 10Be peaks and methane data. The
results indicated that two Greenland warming events that occurred 36
thousand and 45 thousand years ago lagged behind their Antarctic
counterparts (of much lower magnitude) by more than a thousand years.
Moreover, on the average, Greenland climate changes lagged behind
Antarctic changes by 1 to 2.5 thousand years during the period 47,000 to
23,000 BP. Thus, the ocean must be the connecting medium because an
atmospheric link would produce a quicker connection.
A 3000-Year Climatic Record from Biogenic Silica Oxygen Isotopes in
an Equatorial High-Altitude Lake, M. Rietti-Shati, A. Shemesh, and
W. Karlen,Science 281, 980-982 (Aug.14, 1998). Biogenic
opal was collected from a glacial lake on Mount Kenya in East Africa. The
oxygen isotopes of those opal samples were analyzed to provide a record of
the temperature when the opal was formed, which ranged from 1200 to 4200
years ago. The temperature record shows long-term variations, but it also
shows short-term fluctuations with durations on order of centuries. The
long-term variations are attributed to changes in lake temperature, and
the short-term fluctuations to changes in the temperature of the glacial
meltwater entering the lake. Specifically, the data indicate the
occurrence of a period that was warmer than the current climate in
Equatorial East Africa from 2300 to 1500 years before the present. Other
temperature records from Africa and other continents indicate a similar
warm period at that time.
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