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CLIMATE CHANGE AND EXTREME WEATHER - ABSTRACTS
Floods
Mirza, M. Monirul Qader, R. A. Warrick,
and N. J. Ericksen. 2003. "The Implications of Climate
Change on Floods of the Ganges, Brahmaputra and Meghna Rivers
in Bangladesh," Climatic Change, Vol. 57, No. 3, April,
pp. 287-318.
ABSTRACT: Climate change in the future would have implications
for river discharges in Bangladesh. In this article, possible
changes in the magnitude, extent and depth of floods of
the Ganges, Brahmaputra and Meghna (GBM) rivers in Bangladesh
were assessed using a sequence of empirical models and the
MIKE11-GIS hydrodynamic model. Climate change scenarios
were constructed from the results of four General Circulation
Models (GCMs) - CSIRO9, UKTR, GFDL and LLNL, which demonstrate
a range of uncertainties. Changes in magnitude, depth and
extent of flood discharge vary considerably between the
GCMs. Future changes in the peak discharge of the Ganges
River are expected to be higher than those for the Brahmaputra
River. Peak discharge of the Meghna River may also increase
considerably. As a result, significant changes in the spatial
extent and depths of inundation in Bangladesh may occur.
Faster changes in inundation are expected at low temperature
increases than of higher temperature changes. Changes in
land inundation categories may introduce substantial changes
in rice agriculture and cropping patterns in Bangladesh.
Reduction of increased flood hazard due to climate change
requires strengthening of flood management policies and
adaptation measures in Bangladesh.
Mirza, M. Monirul Qader. 2002.
"Global warming and changes in the probability of occurrence
of floods in Bangladesh and implications," Global Environmental
Change, Vol. 12, No. 2, July, pp. 127-138.
ABSTRACT: Bangladesh is very prone to flooding due to
its location at the confluence of the Ganges, Brahmaputra
and Meghna (GBM) rivers and because of the hydro-meteorological
and topographical characteristics of the basins in which
it is situated. On average, annual floods inundate 20.5
per cent area of the country and this can reach as high
as about 70 per cent during an extreme flood event. Floods
cause serious damage to the economy of Bangladesh, a country
with a low per capita income. Global warming caused by the
enhanced greenhouse effect is likely to have significant
effects on the hydrology and water resources of the GBM
basins and might ultimately lead to more serious floods
in Bangladesh. The use of climate change scenarios from
four general circulation models as input into hydrological
models demonstrates substantial increases in mean peak discharges
in the GBM rivers. These changes may lead to changes in
the occurrence of flooding with certain magnitude. Extreme
flooding events will create a number of implications for
agriculture, flood control and infrastructure in Bangladesh.
Reynard, N. S., C. Prudhomme,
and S. M. Crooks. 2001. "The Flood Characteristics
of Large U.K. Rivers: Potential Effects of Changing Climate
and Land Use," Climatic Change, Vol. 48, No. 2-3, February,
pp. 343-359.
ABSTRACT: A continuous flow simulation model (CLASSIC)
has been used to assess the potential impact of climate
and land use changes on the flood regimes of large U.K.
catchments. Climate change scenarios, based on the HadCM2
experiments from the Hadley Centre, are applied to the Severn
and Thames rivers. The analysis shows that, for the 2050s,
the climate change scenarios result in an increase in both
the frequency and magnitude of flooding events in these
rivers. The various ways of applying the rainfall scenario
can have a significant effect on these general conclusions,
although generally do not affect either the direction or
consistency of the changes. While `best guess' land use
changes show little impact on flood response, a 50% increase
in forest cover could counter-act the impact of climate
change. As would be expected, a large change in the urban
cover of the catchments does have a large effect on the
flood regimes, increasing both the frequency and magnitude
of floods significantly beyond the changes due to climate
alone. Further research is required into the potential impacts
of seasonal changes in the daily rainfall and potential
evaporation regimes, land use changes and the interaction
between the two.
Schreider, S. Yu., D. I. Smith,
and A. J. Jakeman. 2000. "Climate Change Impacts on
Urban Flooding," Climatic Change, Vol. 47, No. 1-2,
October, pp. 91-115.
ABSTRACT: This paper estimates changes in the potential
damage of flood events caused by increases of CO2 concentration
in the atmosphere. It is presented in two parts: 1. the
modelling of flood frequency and magnitude under global
warming and associated rainfall intensities and 2. the use
of greenhouse flood data to assess changes in the vulnerability
of flood prone urban areas, expressing these in terms of
direct losses. Three case studies were selected: the Hawkesbury-Nepean
corridor, the Queanbeyan and Upper Parramatta Rivers. All
three catchments are located in southeastern Australia,
near Sydney and Canberra. These were chosen because each
had detailed building data bases available and the localities
are situated on rivers that vary in catchment size and characteristics.
All fall within a region that will experience similar climate
change under the available greenhouse scenarios. The GCMs'
slab model scenarios of climate change in 2030 and 2070
will cause only minor changes to urban flood damage but
the double CO2 scenarios estimated using the Stochastic
Weather Generator technique will lead to significant increases
in building damage. For all the case studies, the hydrological
modelling indicates that there will be increases in the
magnitude and frequency of flood events under the double
CO2 conditions although these vary from place to place.
However, the overall pattern of change is that for the Upper
Parramatta River the 1 in 100-year flood under current conditions
becomes the 1 in 44-year event, the 1 in 35-year flood for
the Hawkesbury-Nepean and the 1 in 10 for Queanbeyan and
Canberra. This indicates the importance of using rainfall-runoff
modelling in order to estimate changes in flood frequencies
in catchments with different physical characteristics.
Droughts
Joubert, A. M., S. J. Mason, J.
S. Galpin. 1996. "Droughts Over Southern Africa in
a Doubled-CO2 Climate," International Journal of Climatology,
Vol. 16, No. 10, pp. 1149-1156.
ABSTRACT: The southern African region is susceptible
to climatic extremes and particularly to extended dry periods.
Possible changes in the probability of dry years under doubled-CO2
conditions are examined using output from the CSIRO nine-level
general circulation model. Changes in annual mean rainfall
are not expected to be significant. However, the model simulates
an increase in the probability of dry years in the tropics,
to the south-west of the subcontinent, as well as over the
western and eastern parts of South Africa and southern Mozambique,
where large percentage increases in the most intense dry
spells are indicated. A decrease in the frequency of dry
years is simulated over much of the interior of the subcontinent
south of 10°S. In regions where the frequency of dry
years decreases, the most severe events occur less often.
The CSIRO nine-level model indicates a shift in the frequency
distribution of daily rainfall events under doubled-CO2
conditions. A small change in the frequency distribution
of daily rainfall events may have further implications for
the frequency of mid-summer droughts during the peak summer
rainfall period of December-February. Increases in the frequency
of mid-summer droughts are simulated over the eastern part
of the subcontinent south of 20°S.
Rosenzweig, C., and D. Hillel.
1993. "The Dust Bowl of the 1930s: Analog of greenhouse
effect in the Great Plains?," Journal of Environmental
Quality, Vol. 22, pp. 9-22.
ABSTRACT:For nine sites in the southern Great Plains,
the decade of the Dust Bowl was consistently warmer than
the 1951 to 1980 "normal." It also tended to be
drier, but less consistently so. At four of the nine sites,
the combination of consistently higher temperatures and
mostly lower precipitation had a cumulative effect over
the 1930s, making the entire decade a period of agricultural
drought as characterized by the Palmer Drought Severity
Index (PDSI). Episodes of extreme drought occurred at many
sites, particularly in 1934 in Nebraska. Temperature and
precipitation changes predicted by two general circulation
models (GCMs) at the upper range of current climate model
predictions for doubled concentrations of CO2 (+4.2°C
and +4.0°C mean global surface air temperature warming)
suggest drought conditions as defined by the PDSI that are
worse than those for the 1930s for all stations. Droughtiness
is projected to increase overall, even when the GCM climate
change scenarios produce little change or even increases
in precipitation. In most instances, the mean GCM-predicted
drought conditions equal or exceed the extreme drought years
of the decade. When dynamic crop growth models were run
in combination with the GCM-predicted climates, simulated
wheat (Triticum aestivum L.) and corn (Zea mays L.) yields
were obtained that were generally lower (~30%) than those
of simulations for the actual climate of the 1930s. The
crop model simulations indicated that the predicted climate
change is likely to be less detrimental to a crop such as
wheat, whose main growing period is in the spring, than
to a typical summer crop such as corn. The overall results
of this study suggest that the Dust Bowl experience of the
1930s may be characterized as a preliminary analog of possible
future climate conditions for the southern Great Plains,
with the important difference that the higher projections
of GCM warming produce more severe climatic consequences
than the Dust Bowl.
Storms
Dorland, C., R. S. J. Tol, and
J. P. Palutikof. 1999. "Vulnerability of the Netherlands
and Northwest Europe to Storm Damage under Climate Change,"
Climatic Change, Vol. 43, No. 3, November, pp. 513-535.
ABSTRACT: Storms occasionally bring havoc to Northwest
Europe. At present, a single storm may cause damage of up
to 7 billion U.S.$, of which a substantial part is insured.
One scenario of climate change indicates that storm intensity
in Northwest Europe could increase by 1-9% because of the
doubling of CO2 concentrations in the atmosphere. A geographic-explicit,
statistical model, based on recent storms and storm damage
data for the Netherlands, shows that an increase of 2% in
wind intensity by the year 2015 could lead to a 50% increase
in storm damage to houses and businesses. Only 20% of the
increase is due to population and economic growth. A 6%
increase could even triple the damage. A simpler model -
based on national average data and combined with a stochastic
storm generator - shows that the average annual damage could
increase by 80% with a 2% increase in wind intensity. A
6% wind intensity increase could lead to an average annual
damage increase of 500%. The damage in Northwest Europe
is about a factor 6 higher than the damage in the Netherlands.
Little potential seems to exist for reducing the vulnerability
to storms in the Netherlands. More attention should be given
to planning at the government level for disaster relief
and to the development of coping strategies.
Tropical Cyclones
Walsh, K., and A.B. Pittock. 1998.
"Potential Changes in Tropical Storms, Hurricanes,
and Extreme Rainfall Events as a Result of Climate Change,"
Climatic Change, Vol. 39, No. 2-3, July, pp. 199-213.
ABSTRACT: Our current understanding of the ability of
climate models to provide insight into the possible impacts
of the enhanced greenhouse effect on the climatology of
tropical cyclones and extreme rainfall events is reviewed.
At present, because of the insufficient resolution of climate
models and their generally crude representation of sub-gridscale
and convective processes, little confidence can be placed
in any definite predictions of such effects, although a
tendency for more heavy rainfall events seems likely, and
a modest increase in tropical cyclone intensities is possible.
In the view of the authors, it would be unwise to exclude
substantial local changes in the climatologies of these
phenomena, especially at a regional (sub-continental) scale.
Royer, J.-F., F. Chauvin, B. Timbal,
P. Araspin and D. Grimal. 1998. "A Gcm Study of the
Impact of Greenhouse Gas Increase on the Frequency of Occurrence
of Tropical Cyclones," Climatic Change, Vol. 38, No.
3, March, pp. 307-343.
ABSTRACT: In order to make inferences on the possible
future changes of tropical cyclogenesis frequency, we apply
the diagnostic computation of the Yearly Genesis Parameter
(YGP) proposed by Gray (1975) to the large-scale fields
simulated by a GCM. The YGP is an empirical diagnostic of
the frequency of Tropical Cyclones (TCs) based on six physical
parameters computed from seasonal means of atmospheric and
oceanic variables. In this paper, we apply the YGP diagnostic
to the results of three climate simulations performed with
the atmospheric General Circulation Model (GCM) of Météo-France:
ARPEGE-Climat. In a control simulation of the current climate,
it is shown that the model has a realistic tropical climatology
and that the computed YGP reproduces the geographical distribution
of the tropical cyclogenesis frequency. The YGP is then
applied to two simulations corresponding to two scenarios
of doubled carbon dioxide concentration. The two experiments
differ by the sea surface temperatures (SSTs) used as a
lower boundary condition. In both simulations the YGP gives
a large increase of total cyclogenesis frequency, but without
extension of the area of possible cyclone genesis. The increase
in YGP is due essentially to the contribution of the ocean
thermal energy factor in the thermodynamical potential.
The dynamical parameters, on the contrary, limit the cyclogenesis
increase and are a major explanation of the difference between
the two experiments. This is in agreement with the results
of the previous similar study of Ryan et al. (1992) concerning
the importance of large-scale atmospheric circulation modifications
on tropical cyclone climatology. After discussing the observed
relationships between ocean surface temperature and large-scale
convection, and questioning the use of a fixed temperature
threshold in the diagnosis of tropical cyclone frequency,
we propose a modification to the YGP consisting in replacing
the thermodynamical potential by a term proportional to
the convective precipitation computed by the GCM. For the
simulation of the present climate this modification affects
only marginally the geographical distribution of tropical
cyclone genesis, but for the doubled CO2 case, the modified
YGP diagnoses a more limited increase in TC genesis in the
Northern Hemisphere and a small reduction in the Southern
Hemisphere, which seems in better agreement with other recent
modelling studies with high resolution climate models (Bengtsson
et al., 1996). We conclude that the modified YGP based on
convective precipitation could serve as a useful diagnostic
of tropical cyclone genesis, and should be tested in simulations
with other GCMs.
