Climate information

Because of its geographical position and by the fact that it is surrounded by oceans, South East Asia experiences a tropical climate with high temperatures and humidity. The region is also influenced by monsoonal winds that cause seasonal intensity of rainfall and is affected by inter-annual climatic variations events such as El Niño and La Niña.

Published reports on future climate change in Southeast Asia are few. The most comprehensive information on climate projections is found on the IPCC’s Third Assessment Report (TAR), which shows that Southeast Asia will become warmer and wetter in all seasons (an increase in annual temperature by 2.49ºC and an increase in annual precipitation by 5.1% in 2080s).

The report notes that extreme events (not limited to ENSO) have increased in intensity and frequency. Based on Southern Oscillation Index (SOI) values, the frequency of El Niño increased from once in 8 years (1876-1976) to once in every 4 (1977-2000). El Niño events with the highest intensity were recorded for 1982 and 1997. The increased numbers of forest fires hotspots are generally related to this El Niño events.

Indonesia

Based on data from BPS (Central Statistics Bureau), the average annual temperature of Indonesia at sea level is around 26-27ºC. The average sunshine in the coastal plain is about 50-70% and the mean humidity is about 80%. Temperature and the relative humidity are more or less constant and uniform throughout the year. The variation in the temperature occurs mostly due to the influence of topography. The annual rainfall is generally above 2,000 mm. In some parts of the country, such as Nusatenggara, the climate is drier with annual rainfall from 700 mm to 1,000 mm.

The dry season occurs in the month of June to September, and is driven by monsoonal winter anticyclone in the southern hemisphere that causes dry southeasterly wind from the Australian continent over Indonesia region. The rainy season occurs in the month of December to March, which is driven by the winter anticyclone in the northern hemisphere. The rests of the months in between the two seasons are known as transition months.

In general, climate change trends for Indonesia will be the same as for South East Asia. Projections on temperature show that it will increase at a lower rate than the global average. On the other hand, projected annual precipitation is expected to increase across Indonesia, with an exception of the south, including Java, Bali and Nusatenggara, regions that are drier.

El Niño events are characterized for causing severe drought. For example, they caused the area of harvested crops to drop by about 1.25 million ha in 1982 and by 1.18 million in 1997 (8.6% and 6.4% respectively).

Philippines

The Climate of the Philippines is tropical marine. It is characterized by relatively high temperature, high humidity and abundant rainfall. The mean annual temperature is 26.6ºC. The coolest month is January (25.5ºC) while the warmest is May (28.3ºC). The variation of temperature across the country is mainly caused by altitude. The average monthly relative humidity varies between 71% in March and 85% in September. Rainfall distribution varies from one region to another as controlled by the direction of the moisture-bearing winds and the orography. The average rainfall ranges from 965 to 4,064 millimeters annually.

Similar to Indonesia, this country experiences two major monsoonal seasons. Rainy season occurs from the months of June to November, and dry season from December to May.

Typhoons have a great influence on the climate and weather conditions of the Philippines. A great portion of the rainfall, humidity and cloudiness are due to the influence of typhoons. Their movements generally follow a northwesterly direction during the winter anticyclone in the northern hemisphere.

Projections for future climate do follow similar trends as those for the region, as described above.