The policy of Doi Moi, first introduced in 1986, has made a dramatic impact on the reduction of poverty in Viet Nam. From a high of 70% in 1990, the poor, as a percentage of the population, fell to 58% in 1993, 37% in 1998 and around 29% in 2002. Worldwide, the decade has also experienced a surge in hydrometeorological natural disasters (floods, droughts, extreme temperature events and windstorms). In developing countries, the frequency of hydrometeorological natural disasters has increased nearly 3-fold from 55 events per year in the 70s to around 140 events in the 90s. Vietnam has had more than its share of natural disasters. The floods in 1999 in Central Vietnam caused an estimated damage of USD 340 million and had set the development of the region back for many years. Vietnam, with its long coast line and low lying plains where most people live, is particularly exposed to hydrometeorological natural disasters.
This paper will describe the hydrometeorological natural hazards to which Vietnam has been exposed over past decades and the vulnerability of the country to such hazards. We will then briefly explore the question of how such hazards may change in the future, due to global climate change. The paper5 will also describe briefly the policies and activities that the Vietnamese Government has implemented to address hydrometeorological natural hazards.
1. Climate Change – The Global Perspective
The assessment published by the Intergovernmental Panel on Climate Change in 2001 [IPCC, 2001a] notes it is very likely6 that globally the 1980s was the warmest decade, and 1998 the warmest year, in the instrumental record (1861 – 2000). The increase in surface temperature over the 20th century for the Northern Hemisphere is likely to have been greater than for any other century in the past 1000 years. The IPCC concluded: “There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities”.
The IPCC also concluded that over the 20th Century it is very likely that:
- global surface temperature increased by 0.6 ± 0.2°C;
- the number of hot days increased;
- the number of frosts decreased for nearly all land areas, likely that Northern Hemisphere continental precipitation (rain and snowfall) increased by 5-10%;
- heavy precipitation events increased at mid- and high northern latitudes, and that the frequency and intensity of drought increased in some regions.
Over the 20th Century, globally averaged sea level increased at an average of 1 to 2 mm per year, and there was an increased frequency of coral reef bleaching, especially during El Niño events. During the last forty years the growing season increased by about 1 to 4 days per decade years in the higher latitude Northern Hemisphere, and global weather-related economic losses (inflation adjusted) rose by an order of magnitude. Part of this trend in economic losses was linked to socio-economic factors, and part to climatic factors.
The 2001 IPCC assessment provided projections of climate changes expected to occur over the 21st Century, for a range of plausible greenhouse gas emission scenarios (the so-called SRES scenarios, which do not include the effect of any policies specifically directed at decreasing greenhouse gas emissions). These projections are for a rise in globally averaged surface temperature of 1.4 to 5.8°C – a rate of global warming very likely to be without precedent over the last 10,000 years. Globally averaged annual precipitation is projected to increase, though at regional scales both increases and decreases are projected of typically 5 to 20%. Global mean sea level is projected to rise by somewhere between 9 and 88 cm by 2100, but with significant regional variations.
Changes are also expected in various climatic extremes through the coming century. For example more hot days and heat waves and fewer frost days and cold waves, are very likely over nearly all land areas. More intense rainfall events are very likely over many areas, with associated increased risk from flood, landslide, avalanche and mudslide. Increased summer drying and risk of drought is likely over most midlatitude continental interiors, and increased variability is likely in precipitation from the Asian summer monsoon. Also, increases are likely over some areas in tropical cyclone peak wind intensities, and mean and peak precipitation intensities in these cyclones.
2. Climate Variability and Change over Vietnam
Predictions of climate change at regional or smaller scales are subject
to higher uncertainties than projections of globally-averaged changes. Also, the
effects of natural climate variations (for example those associated with the El Niño
and La Niña) show up more strongly in climate statistics from smaller areas,
and make it more difficult to unambiguously detect trends and determine whether these
are caused by human activities.
The Working Group II Report of the 2001 IPCC Assessment contains a set of regional chapters (IPCC, 2001b). However the chapter that includes Vietnam covers the whole of Asia within 55 pages, from Siberia down to Indonesia, and from Syria across to Japan. This means there is little specific detail given on Vietnam. Relevant points regarding projections out to 2100 from the Working Group II report and the chapter about regional climate information in the Working Group I report (IPCC, 2001c) includes:
- For South-East Asia as a whole, warming is likely to be less than the global average in June - July – August
- December-January-February precipitation is likely to show little change in South-East Asia.
- Modelling studies of tropical cyclones suggest it is likely that peak wind intensities will increase by 5 to 10% and mean and peak precipitation intensities by 20 to 30% in some regions.
- 23% of the population of Vietnam would be exposed to a sea level rise of 100cm (about twice the “mid-range” IPCC projection for 2100).
climate change in Vietnam is provided below. This is drawn from the work of
organizations such as the Vietnamese Hydrometeorological Service (responsible for
the National Action Plan of Vietnam for climate change issues), the Asian Disaster
Preparedness Centre (ADPC, 2003), the Centre for Environmental Research,
Education and Development in Hanoi, and international collaborators (e.g. Kelly and