RECENT CLIMATE TRENDS
Over the past four decades, there have been noticeable changes in Vietnam’s climate particularly
regarding rise in temperatures and sea level:
18
Mean annual temperature has increased by 0.4oC since 1960, with the rate of increase more
rapid in the dry seasons (November, December, January and February, March, April) and more
intense in the southern parts of the country.
The frequency of ‘hot’ days and nights has increased significantly since 1960 in every season,
with an especially high rate of ‘hot’ day increase between September and November, and
‘hot’ night increases in June to August.
The annual frequency of ‘cold’ days and nights has decreased significantly,
19 with the rate of
decrease being strongest in December, January and February in each case.
Rainfall in Vietnam is characterized by high variability on both annual and inter-decadal time
scales, which make trends since 1960 difficult to categorize. Mean rainfall over Vietnam does
not show any statistically significant change since 1960, and neither does the proportion of
rainfall falling in heavy events, nor the maximum amount failing in 1-day or 5-day events.
The number of cold fronts affecting Vietnam has decreased since the 1970s.
20
The trajectory of typhoons affecting Vietnam appears to have moved southward in recent
years, and the peak month for landfall has shifted from August in the 1950s to November in
the 1990s.
21
The frequency of tropical cyclones operating in the East Sea has been observed to have
decreased over the past several decades, although the frequency of tropical cyclones that
affect Vietnam has increased by 0.43 event per decade in the past 50 years.
22 Higher-intensity
typhoons are noted to be occurring more frequently.
23
Regarding sea level change along the coast, observations show that average sea level has
decreased by 0.20 cm per year (1965-2006) at Hon Dau station, by 0.260 cm per year (1978-
2006) at Son Tra station, and has increased by 0.398 cm per year (1981-2006) at Vung Tau
station.