Impact on VietnamImpact on VietnamIn order to forecast the change in climate likely to affect Vietnam as global warming develops, it is necessary to use computer models of the climate system.
Because of uncertainties in the science of climate change, it is not possible to give firm predictions but a range of possible projections can be defined.
Climate model results have been used to assess likely changes in Vietnam's climate over the period to 2100 and estimates are presented here for the likely range of temperature and rainfall trends for the areas surrounding Hanoi and Ho Chi Minh City. The projections are based on the 1992 IPCC assessment.
According to the most likely estimate, annual temperatures in the area of Hanoi may rise by just over 1 deg. C by the year 2050 and by close to 2.5 deg. C by the year 2100. This is almost ten times the warming rate experienced over the past 80 years. If the most severe projections are correct, temperatures may rise by over 4 deg. C by the end of the 21st century.
The future change in temperature (left) and precipitation (right) for the area of Hanoi.
The central line indicates the most likely estimate and the shaded area shows the range
of uncertainty.
There is considerable uncertainty as far as the regional change in rainfall is concerned.
Although the forecasts tend towards an increase in rainfall amounts in the Hanoi area, the range of possibilities spans a decline of close to 15% below the present-day average through to an increase of over 30% by the year 2100. The most likely estimate is a minor increase in rainfall of 2% or so by the year 2050 and 5% by the year 2100.
The increase in rainfall in North Vietnam is consistent with more northward penetration of the summer monsoon.
Analysis of future conditions in the area of Ho Chi Minh City indicates that the change in temperature and rainfall in the south may not be as great.
The future change in temperature (left) and precipitation (right) for the
area of Ho Chi Minh City. The central line indicates the most likely estimate
and the shaded area shows the range of uncertainty.
The most likely projection is a rise in temperature of around 2 deg. C and a very slight increase in rainfall by the end of the 21st century. It is, however, possible that the change in climate may be more severe, with a rise in temperature of 3.6 deg. C and a 5% decline in rainfall amounts by the year 2100.
Available moisture throughout the country, and particularly in the south, is likely to be reduced due to increased evaporation as temperatures rise. This could well lead to a marked increase in the frequency of droughts and may prove the major impact of climate change.
Tropical cyclone numbers may also be affected by the regional change in climate, with an increase in frequency and, perhaps, strength expected to occur.
By the year 2100, global-mean sea level may stand between 32 and 64cm above the present-day level, with a rise of 45cm the most likely estimate. (In considering the regional implications of this change, it is necessary to take account of local tectonic and anthropogenic factors.)
The likely global trend represents an increase in the rate of change in sea level along Vietnam's coast by a factor of two to three. For Hondau, this would mean a rise in sea level of up to 64cm by the year 2100, compared with a rise of about 20cm if the trend of the most recent decades continues.
Further work is needed to provide a more detailed projection of Vietnam's climate in years to come. The results of climate modelling experiments must be supplemented by understanding of regional conditions based on the experience of Vietnamese experts.
Based on material provided by
Dr Nguyen Huu Ninh, Director, Center for Environment Research Education and Development
Dr Hoang Minh Hien, Hydrometeorological Service
Professor Nguyen Ngoc Thuy, Director, Marine Hydrometeorological Centre
Dr Tranh Thanh Xuan, Hydrometeorological Service
"Impact on Vietnam: Sea level rise impacts"
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