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 9, NUMBER 1, JANUARY 1996
"The 1990-1995 El Niño-Southern Oscillation Event: Longest on
Record," K.E. Trenberth (Clim. & Global Dynamics Div., NCAR, POB 3000,
Boulder CO 80307), T.J. Hoar, Geophys. Res. Lett., 23(1), 57-60,
Jan. 1, 1996.
Statistical analysis of the 113-year record of tropical Pacific data shows
that both the recent trend for more ENSO events since 1976 and the prolonged
1990-1995 ENSO event are unexpected. This opens the possibility that the ENSO
changes may be partly caused by the observed increase in greenhouse gases.
"Recent Climatic Change in the World's Drylands," M. Hulme
(Clim. Res. Unit, Univ. E. Anglia, Norwich NR4 7TJ, UK), ibid., 61-64.
Precipitation and temperature trends in nine dryland regions are analyzed
for the period 1900 to 1994. No widespread desiccation in dryland climates is
found, the African Sahel being the only region to demonstrate a significant
drying trend. However all dryland regions have warmed, with the majority of the
warming probably being unrelated to regional dryland effects.
"The Elastic Response of the Earth to Interannual Variations in
Antarctic Precipitation," C.P. Conrad (Dept. Earth, Atmos. & Planetary
Sci., Mass. Inst. Technol., Cambridge MA 02139), ibid., 22(23),
3183-3186, Dec. 1, 1995.
Performs numerical experiments which show that the accumulation of ice mass
in Antarctica is a highly variable process and can cause large variations in
both sea level rise and in the Earth's elastic response to mass accumulation. If
climate change significantly accelerates mass changes on the large ice sheets,
these long-term trends could be detected in a few years by crustal displacement
"Twentieth-Century Variability in Snow-Cover Conditions and
Approaches to Detecting and Monitoring Changes: Status and Prospects," R.G.
Barry (NSIDC/CIRES, Univ. Colorado, Boulder CO 80309), J.-M. Fallot, R.L.
Armstrong, Prog. in Phys. Geog., 19(4), 520-532, Dec. 1995.
This review discusses which indices are the most suitable for detecting
trends in snow cover, and illustrates the use of passive microwave data for the
continental and regional scales. Data availability is also reviewed, and newly
available records for the former USSR discussed. Summarizes model projections of
changes in snow cover in several mountain regions that may result from
"Dynamic Contribution to Hemispheric Mean Temperature Trends,"
J.M. Wallace (Dept. Atmos. Sci., AK-40, Univ. Washington, Seattle WA 98195), Y.
Zhang, J.A. Renwick, Science, 270(5237), 780-783, Nov. 3, 1995.
A statistical study performed on Northern Hemisphere surface air
temperatures, for the period 1900 through 1990, relates to the identification of
a greenhouse "fingerprint" as predicted by climate models. Much of the
temporal variability of monthly, hemispheric mean temperature anomalies is
related to the amplitude of a distinctive spatial pattern of cold oceans and
warm continents. The authors argue that the variability associated with this
pattern is dynamically induced by the movement of warm and cold air masses, and
is not necessarily an integral part of the fingerprint of global warming.
However, the amplitude of the pattern increases between 1975 and 1990, and since
it does contain elements of the greenhouse warming fingerprint, it is not clear
whether greenhouse warming is a factor in this recent trend.
"Atmospheric Methane at Mauna Loa and Barrow Observatories:
Presentation and Analysis of in situ Measurements," E.J.
Dlugokencky (CMDL, NOAA, 325 Broadway, Boulder CO 80303), L.P. Steele et al.,
J. Geophys. Res., 100(D11), 23,103-23,113, Nov. 20, 1995.
Describes several semi-continuous, in situ measurements made between
1986 and 1994, and examines features of the records ranging from the diurnal
cycle to seasonal cycles and trends. The semi-continuous nature of the records
are necessary for understanding implications concerning methane sources and
sinks. The average trend at Mauna Loa was 9.7 ppb per year, decreasing at a rate
of 1.5 ppb per year; the trend at Barrow was 8.5 ppb per year, decreasing at 2.1
ppb per year.
"Increase in the Atmospheric Nitrous Oxide Concentration During the
Last 250 Years," T. Machida (Natl. Inst. Environ. Studies, 16-2 Onogawa,
Tsukuba 305, Japan), T. Nakazawa et al., Geophys. Res. Lett., 22(21),
2921-2924, Nov. 1, 1995.
Analysis of air samples extracted from an Antarctic ice core yielded a time
history of N2O with a precision of ±2 ppbv that is clearly less scattered
than previous analyses. Concentrations of N2O averaged about 276 ppbv in the
18th century, began to increase in the mid-19th century and reached 293 ppbv
around 1965. The trend, believed to be anthropogenic, is compared with results
of other studies.
"Evaporation Losing Its Strength," T.C. Peterson (NCDC, NOAA,
Asheville NC 28801), V.S. Golubev, P. Ya. Groisman, Nature, 377(6551),
687-688, Oct. 26, 1995.
Brief correspondence reporting a downward trend in evaporation of water as
measured in pan evaporimeters in the U.S. and the former Soviet Union (FSU).
Results imply that for large regions of the globe, the terrestrial evaporation
component of the hydrological cycle has been decreasing, and provide a partial
explanation for observed increases in runoff over the past two decades in the
European part of the FSU and the northern U.S. Results are also consistent with
speculation by Karl et al. that increased cloud cover may explain observed
decreases in daily temperature range.
"Trends in Air Temperature and Precipitation for Canada and
Northeastern USA," T.Y. Gan (Dept. Civil Eng., Univ. Alberta, Edmonton AB
T6G 2G7, Can.), Intl. J. Climatol., 15(10), 1115-1134, Oct.
Reports on an extensive statistical analysis of regional trends over the
period 1949-1989 based on carefully selected station records. Western Canada has
experienced significant warming in January and March, and to a limited extent in
April, May, and June, but no trend or some cooling was found in eastern Canada
and the northeastern U.S. No significant trend appeared in the precipitation
"Testing for Change in the Frequency of El Niño Events,"
A.R. Solow (Woods Hole Oceanog. Inst., Woods Hole MA 02543), J. Clim.,
8(10), 2563-2566, Oct. 1995.
Analysis of the El Niño record over the period 1525-1987 shows an
apparent increase in frequency, but it is consistent with an overall increase in
the completeness of the historical record. When the analysis is repeated for the
later part of the period and for strong events alone, no trend is found.
"Variations and Change in South American Streamflow," J.A.
Marengo (CPTEC, INPE, Rod. Presidente Dutra Km. 40, 12630-000 Cachoeira
Paulista, Sao Paulo, Brazil), Clim. Change, 31(1), 99-117, Sep.
Statistical analysis of long-term records of streamflow and rainfall in
large portions of South America show no clear evidence of trend or change in the
mean streamflow resulting from a climate change, even though significant trends
toward drier conditions have been found for rivers in parts of Peru and Brazil.
The effects of Amazon deforestation are not noticeable on the 1903-1992
interannual variability of the Rio Negro time series at Manaus nor in rainfall
"Greenland Ice Sheet Thickness Changes Measured by Laser Altimetry,"
W. Krabill (Lab. Hydrospheric Proc., NASA Wallops Flight Facility, Wallops Is.
VA 23337), Geophys. Res. Lett., 22(17), 2341-2344, Sep. 1, 1995.
Airborne laser-altimetry surveys that began in 1980 provide an indication of
ice-thickness changes across southern Greenland in unprecedented detail, and
show a thickening in western Greenland of up to two meters between 1980 and
1993. It is not yet possible to say whether this increase represents a long-term
trend, or the cumulative effect of interannual variability of snow-accumulation
"Ocean Variability and Its Influence on the Detectability of
Greenhouse Warming Signals," B.D. Santer (Lawrence-Livermore Natl. Lab.,
POB 808, Livermore CA 94550), U. Mikolajewicz et al., J. Geophys. Res.,
100(C6), 10,693-10,725, June 15, 1995.
Describes extensive analyses of output from the Max Plank Institute's
coupled ocean-atmosphere GCM that are intended to estimate when detectable
greenhouse warming signals might be observed in the ocean. Explores sources of
uncertainty related to the natural variability or noise, and sources inherent in
any time-evolving signals. By using multiple indicators of change and
statistical manipulation of data to reduce the signal-to-noise ratio, detection
time can be reduced to 10-45 years.
"Temperature Histories from Tree Rings and Corals," E.R. Cook
(Tree Ring Lab., Lamont-Doherty Earth Observ., Rte. 9W, Palisades NY 10964),
Clim. Dynamics, 11(4), 211-222, May 1995.
Recent temperature trends in long tree-ring and coral proxy temperature
histories from around the world are examined to objectively determine how
anomalous twentieth century temperature changes have been. Overall, the regional
temperature histories support the larger-scale evidence for anomalous twentieth
century warming based on instrumental records, but this warming cannot be
confirmed as unprecedented in all regions.
"A Note on the Recent Increase of Solar UV-B Radiation over Northern
Middle Latitudes," C.S. Zerefos (Lab. Atmos. Phys., Aristotle Univ.,
Thessaloniki, Greece), A.F. Bais et al., Geophys. Res. Lett., 22(10),
1245-1247, May 15, 1995.
Three years of measurements at 40° N support earlier findings of
increased solar UV-B irradiances under all-skies conditions associated with
observed ozone decline during the period.
"Changes in Winter Air Temperatures Near Lake Michigan, 1851-1993,
as Determined from Regional Lake-Ice Records," R.A. Assel (Great Lakes ERL,
NOAA, 2205 Commonwealth Blvd., Ann Arbor MI 48105), D.M. Robertson, Limnol.
Oceanog., 40(1), 165-176, Jan. 1995.
Used data from two locations in Michigan and Wisconsin that have among the
longest ice records available near the Great Lakes. Freeze-up and breakup dates
were translated into changes in air temperature using empirical and
process-driven models. Deduced temperatures show a 1.0-1.5° C increase in
late winter and early spring about 1890, additional warming of 1.2° C in
March since about 1940, and a warming of 1.1° C in January-March since
about 1980. Ice records will continue to provide an indication of anticipated
climatic warming, not only because of the large response of ice cover to small
changes in air temperature, but also because these records integrate climatic
conditions during the winter-spring seasons, when most warming is forecast to
"Study of Linear Trends of Time Series of Solar Radiation," Yu.
V. Zhitorchuk (Voeykov Main Geophys. Observatory, Russia), Atmos. &
Oceanic Phys., 30(3), 368-374, Dec. 1994. English edition.
Presents statistical analysis of data from 160 actinometric stations in the
CIS, Baltic and Transcaucasian regions, from 1960 to 1987. Over most of the
territory there was a significant per decade decrease in direct and global solar
radiation of -6.3% and -2.5%, respectively. Suggests that the drop in global
radiation is a manifestation of a negative cloud `feedback which helps offset
the rise in air temperature caused by the greenhouse effect.
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Index of Abbreviations