The Effects of Hydrometeorological Natural Hazards on Vietnam Development since Doi Moi, and Implications of Global Climate Change for Future Hazards

Tan Pham

Globally, the climate is changing 

From Fig 2-3, Synthesis Report, IPCC Third Assessment Report 

IPCC, 20001: “There is new and stronger evidence that most of the warming over the last 50 years is attributable to human activities”

Larger Global Changes are Expected in Future

IPCC projections for ~2100 AD, for the SRES emission scenarios are:

• Global temperature increase 1.4° to 5.8°C


• Regional changes in rainfall (+ and -)


• Global sea level rise 9 cm - 88 cm


• More hot days and heat waves


• More intense rainfall over some areas with increased flood, landslide, mudslide risk


• Increased rainfall variability in Asian summer monsoon


• Tropical cyclones: Peak wind intensities likely to increase 5 to 10%, peak rain intensity 20 to 30% in SOME regions 

 Vietnam’s temperature has increased over the past century

 

HadCRU Gridded Temperatures, annual, for box 10-20°N, 105-115°E
(Data from UK Met Office Hadley Centre + CRU Norwich)

The temperature over the region 10 to 20°N and 105 to 110°E trended upwards by 0.8 +/- 0.1°C over the 20th Century

Sea level has increased at some locations

 

At Hon Dau (the longest & most reliable record), there was a positive trend of 1.9 mm/year from 1995-1990 (Granich et al, 1993)

Varying decadal trends have been observed in Vietnam rain and typhoons

Typhoon Imbudo, July 24 2003, DSMP Satellite

• 1960s - 90s annual rainfall increase in north, decrease in south¹.


• Changes in runoff (eg increases in Mekong flow at Vientiane in 1960s) caused by combination of human influences & climate variations¹


• Since 1900 typhoon numbers have ranged from 1-12 per year², with typically³
  • More typhoon landfalls in La Niña years
  • Stronger typhoon intensity in El Niño years


• No firm evidence from observations to date, of long-term trend in typhoons²

References: ¹ Granich et al, 1993; ² Kelly & Adger, 2000; ³ Hoang Minh Hien, 2000

Vietnam is Very Vulnerable to Floods & Typhoons

Date	Location	Impacts
August 1996	Red River	Large floods plus high tides caused erosion to 120 km of dyke sections and threatened various essential economic activities
November 1996	Coastal Southern Vietnam	Typhoon Linda. Massive losses to life and property. 2,900 people killed or missing, 108,000 houses destroyed, 22,000 ha of rice fields washed away, 2,900 fishing ships sunk, 136,000 ha of shrimp and fish ponds broken
November & December 1999	Central Vietnam	Extremely heavy rainstorms inundated a large area, with massive losses (Estimate US$340M).
Three months in 2000	Mekong Delta	Floods affecting around 4 million people and causing about US$3 billion losses in Mekong Delta.
2001-02	Mekong Delta	Long lasting inundation affected 2 million people and caused economic loss of around US$100 million in 2001 and US$50 million in 2002

Sources: ADPC, 2003; Duong Lien Chau, 2000

Projected Changes over Vietnam: Temperature & Rainfall

• Annual mean temperature increase by 0.3°C to 2.5°C by 2070


• Largest rises (~2.5°C) inland.


• Increase ~1.5°C in coastal parts of Central & Mekong regions


• More very hot days


• Annual average rainfall might not be affected much by greenhouse warming for several more decades


• Areas affected by Northeast monsoon (including Central Vietnam) may get annual rainfall increases of up to 10% from 2050


• Frequency of extreme rainfall events likely to increase

(Projections reference: ADPC, 2003)

Projected changes: Sea level & Typhoons

DSMP Satellite, NOAA Website

• IPCC projects global mean sea level increase of 9 to 88 cm by 2100


• ADPC (2003) suggests 1 m Vietnam scenario for 2100, because of unknowns in future storm patterns & intensities which might affect storm surge & waves


• Vietnamese coastal areas MIGHT experience significant increases in peak rainfall, wind speed & storm surge / waves associated with typhoons


• IPCC (2001) suggested 5-10% increase in peak wind, 20-30% in peak rainfall in typhoons in SOME parts of globe - but did not say WHERE

Future Vulnerability: Typhoons, sea level, floods

Sea Level: 1 metre rise would subject 17 million people to annual flooding, of whom over 14M live in Mekong Delta provinces Projected increase in frequency of heavy rainfall events would give more flash floods, greater runoff	Typhoons presently account for about 80% of disasters affecting Vietnam (ADPC, 2003) Thus possible future increase of typhoon peak wind and rain intensity, & associated wave & storm surge effects is of great concern
Importance of National Action Plan of Vietnam for Climate Change issues, coordinated by the Vietnam Hydrometeorological Service.

Conclusions

Need to incorporate not only natural hazards but also global climate change into future development plans