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The Indian Monsoon and
Climate Change
The Indian and South Asian monsoon affects the lives
of more than one third of the world’s population. How
might it change in the future?
Climate models suggest an increase in summer
rainfall over India – on average
Simulations with the Met Office coupled ocean-atmosphere
model (HadCM3) suggest a robust Asian summer monsoon indeed precipitation increases by around 5% over India.
The strengthening occurs due to a warmer Indian Ocean that
provides additional moisture for convection.
Model errors may prevent more authoritative projections of the
future climate. Tests to examine such errors in this model suggest
increases in the monsoon are qualitatively correct.
June-Sept rainfall changes for 2xCO2
850mb wind changes for 2xCO2
Surface temperature changes for 2xCO2
Of much greater interest to the agrarian societies of South Asia is the effect of climate
change on annual and intraseasonal variations in the monsoon…
Water consumers need advanced
warning of long and short term
variations in the monsoon in order to
adapt their requirements.
The dramatic break of July 2002.
Intraseasonal variability: during the
summer, active and break periods of
intense and reduced precipitation have a
dramatic impact on water supplies
available for agriculture.
Interannual variability: seasonally
Mumbai flooding in August 2005.
persistent floods or droughts can be
devastating to the Indian economy if
not correctly forecast.
PDF of daily rainfall
anomalies in
HadCM3. An
increased number of
very wet and dry days
are predicted during
the monsoon season.
PDF of summer rainfall
totals in HadCM3 shows
increased interannual
variability. The risk of
sustained heavy rain is
particularly enhanced.
Climate change may not manifest itself in simple changes alone. Variations on decadal
timescales can also influence the monsoon system…
Interdecadal variability: observed relationships between the monsoon and the El Niño-Southern
Oscillation over the Pacific have waxed and waned over the last century. Some measure of ENSO is often
used in statistical forecasts of the monsoon.
One version of the HadCM3 model suggests that ENSO may change between distinct regimes at 2xCO 2.
The regimes and their impact on the monsoon demonstrate that climate change may have more profound
effects than previously thought.
East Pacific seasurface temperatures
show long periods of
irregular and biennial
oscillation in HadCM3
at 2xCO2.
Dr Andrew Turner, Dr Pete Inness and Prof Julia Slingo
Correlations
between monsoon
rainfall and ENSO
are very different in
each regime.
Contact: [email protected]
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Global warming and climate change is one of the most extensively researched and
discussed topical issues affecting the environment. Although there are enough historical
evidence to support the theory that climate change is a natural phenomenon, many
research scientists are widely in agreement that the increase in temperature in the 20th
century is anthropologically related.
The associated effects are the variability of rainfall and cyclonic patterns that are being
observed globally. In Southeast Asia the link between global warming and the seasonal
atmospheric flow during the monsoon seasons shows varying degree of fuzziness. This
study investigates the impact of climate change on the seasonality of monsoon Asia and
its effect on the variability of monsoon rainfall in Southeast Asia.
The comparison of decadal variation of precipitation and temperature anomalies before the
1970s found general increases which were mostly varying. But beyond the 1970s, global
precipitation anomalous showed increases that almost corresponded with increases in
global temperature anomalies for the same period.
There are frequent changes and a shift westward of the Indian summer monsoon.
Although precipitation is observed to be 70% below normal levels, in some areas the
topography affects the intensity of rainfall. These shifting phenomenon of other monsoon
season in the region are impacting on the variability of rainfall and the onset of monsoons
in Southeast Asia and is predicted to delay for 15 days the onset of the monsoon in the
future.
The variability of monsoon rainfall in the SEA region is observed to be decadal and the
frequency and intensity of intermittent flooding of some areas during the monsoon season
have serious consequences on the human, financial, infrastructure and food security of the
region.
Schewe and Levermann (2012) predicted the increasing temperature in the late 21st
century and early 22nd century will cause frequent changes and shifts to the monsoon
precipitation up to 70% below normal levels. Not only will this affect the Indian summer
monsoon, but the onset of monsoon over Southeast Asia may also be delayed up to 15
days