25 The frequency and intensity of tropical cyclones originating in the Pacific Ocean is increasing, affecting the Philippines and
Viet Nam in particular MMD, 2009. The frequency of typhoons increased more than fourfold between 1990 and 2003 ADB, 2009. In Viet Nam, communities have reported that storms are more violent, bringing heavier rainfall and flooding
Jennings and Magrath, 2009. Typhoons are occurring later in the year and now occur in southern regions, where they were previously uncommon ADB, 2009; MONRE, 2003; Vu, 2011. Coastal communities are reporting stronger and higher
tides that bring seawater further upriver than before Jennings and Magrath, 2009. Communities in eastern Cambodia have also experienced more frequent and severe storms RECOFTC, 2012.
Climate-related hazards have increased over the past five decades, most commonly flooding, landslides and water- or vector- borne diseases Boer and Perdinan, 2008. Severe droughts and floods are regularly affecting the region, with conditions
becoming more variable and frequent. For example, record-high water levels recorded in the Mekong River in 2008 were followed shortly after by record lows RECOFTC, 2013. Indonesia experienced a severe drought in 1997–1998, influenced
by the ENSO, followed by severe flooding associated with the LNSO in 2001. Lao PDR has seen the number of severe floods and droughts increase in the past three decades GOL, 2009.
Sea levels are currently rising by 1–3 mm every year. Forest fires have also increased over the past 20 years. These are attributed to the rise in temperatures and a decline in rainfall, in combination with changing land use patterns. Peat fires in
Indonesia in the 1997–1998 El Niño dry seasons affected more than 2 million ha of land and may have emitted up to 2.57 petagrams of carbon
29
into the atmosphere MMD, 2009.
3.1.2 Projected trends
Future climate scenarios indicate that, without concerted action to reduce greenhouse gas emissions, annual mean temperatures will continue to rise. The latest climate projections suggest a 2°–4°C increase by the end of this century
ADB, 2009; World Bank, 2012. Temperature increases in Southeast Asia are expected to be more extreme than the global average, with possible increases of up to 6°C by 2050 in certain parts of the Mekong River Basin Mekong ARCC, 2013.
In general, wet seasons are expected to become wetter, dry seasons will become drier RIMES, 2011. The dry season will also become longer, leading to more frequent drought conditions. Greater variations in river flows are expected;
for example, water levels in the Mekong River are expected to be higher in the wet season and lower in the dry season, suggesting increased risks of both flooding and water shortages. Rainfall patterns will become increasingly unpredictable,
with more rain falling in shorter periods of time, increased surface run-off and risk of flooding Hoanh et al., 2004. Heavy rains, floods and storms will damage crops, farmland, livestock, fisheries and forests and, combined with land use changes,
may result in greater soil erosion and more frequent landslides.
Sea levels in Cambodia and Myanmar are projected to rise by 15 cm by 2030 and up to 45 cm by 2070. Sea level in Viet Nam is expected to rise by 33 cm by 2050 and by as much as 1 m by 2100 ISPONRE, 2011. In Malaysia, sea levels have
been rising by 1.3 mm per year and are projected to rise by 50 cm by 2050 NRE, 2011. Sea-level rise, combined with stronger storms and storm surges, present a serious threat to coastal settlements.
These impacts will have considerable adverse impacts on a range of natural and human systems, such as food production, water supply, infrastructure, property, economic activity, human health and security. Without greater effort on mitigation
and adaptation, the costs associated with future climate change in the region could be as high as 6.7 percent of GDP per year ADB, 2009. The impact of climate change will be disproportionally felt by poor people in rural areas because their
incomes, livelihoods and survival are more dependent upon natural resources and agriculture.
3.1.3 Projected impacts of climate change on forests and forest-dependent people
