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Cambodia - Climate

Temperatures in Cambodia can range from 10 degress to 38 degress Celsius. The country is subject to tropical monsoons, with the southwest monsoon blowing inland in northeasterly direction bringing moisture-laden winds from Gulf of Thailand/Indian Ocean from May to October with period of heaviest precipitation between September and October. The northeast monsoon blowing in southwesterly direction toward coast ushers in dry season, from November to March, with period of least rainfall between January and February.

Cambodia's climate--like that of the rest of Southeast Asia--is dominated by the monsoons, which are known as tropical wet and dry because of the distinctly marked seasonal differences. The monsoonal airflows are caused by annual alternating high pressure and low pressure over the Central Asian landmass. In summer, moisture-laden air--the southwest monsoon--is drawn landward from the Indian Ocean. The flow is reversed during the winter, and the northeast monsoon sends back dry air. The southwest monsoon brings the rainy season from mid-May to mid-September or to early October, and the northeast monsoon flow of drier and cooler air lasts from early November to March. The southern third of the country has a two-month dry season; the northern two-thirds, a four-month one.

Short transitional periods, which are marked by some difference in humidity but by little change in temperature, intervene between the alternating seasons. Temperatures are fairly uniform throughout the Tonle Sap Basin area, with only small variations from the average annual mean of around 25°C. The maximum mean is about 28°C; the minimum mean, about 22°C. Maximum temperatures of higher than 32°C, however, are common and, just before the start of the rainy season, they may rise to more than 38°C. Minimum temperatures rarely fall below 10°C. January is the coldest month, and April is the warmest. Typhoons--tropical cyclones--that often devastate coastal Vietnam rarely cause damage in Cambodia.

Cambodian farmers grow rice in both seasons. Cambodia’s rainy season typically arrives in May and ends in October and dry season runs from November until April. Having land to farm crops, especially rice, is central to the lives of many Cambodians. It is what gives them a sense of security, community and family. Eighty-five percent of Cambodia’s approximately 16 million people depend on subsistence agriculture for their livelihoods.

The total annual rainfall average is between 100 and 150 centimeters, and the heaviest amounts fall in the southeast. Rainfall from April to September in the Tonle Sap Basin-Mekong Lowlands area averages 130 to 190 centimeters annually, but the amount varies considerably from year to year. Rainfall around the basin increases with elevation. It is heaviest in the mountains along the coast in the southwest, which receive from 250 to more than 500 centimeters of precipitation annually as the southwest monsoon reaches the coast.

This area of greatest rainfall, however, drains mostly to the sea; only a small quantity goes into the rivers flowing into the basin. The relative humidity is high at night throughout the year; usually it exceeds 90 percent. During the daytime in the dry season, humidity averages about 50 percent or slightly lower, but it may remain about 60 percent in the rainy period.

Cambodia is prone to extreme weather events, especially floods, droughts and typhoons. Climate change is predicted to increase the frequency and intensity of such events. The Cambodian population is highly vulnerable to the impacts of these events due to poverty; malnutrition; agricultural dependence; settlements in flood-prone areas, and public health, governance and technological limitations. Water-borne diseases are of particular concern in Cambodia, in the face of extreme weather events and climate change, due to, inter alia, a high pre-existing burden of diseases such as diarrhoeal illness and a lack of improved sanitation infrastructure in rural areas.

Cambodia is ranked one of the most vulnerable countries in the world to climate change. Cambodia is identified as having ‘extreme’ vulnerability to climate change, ranking eighth out of 193 countries in Maplecroft’s Climate Change Vulnerability Index in 2014, based on a composite of exposure to extreme weather events (predominantly floods and droughts), sensitivity and adaptive capacity.

Many of its people rely on agriculture, and the changes to the country’s climate, leading to more droughts or more floods, makes them particularly vulnerable. In Asia, Cambodia ranks with Bangladesh and the Philippines in terms of its exposure to climate change, in large part due to its dependence on a changing monsoon pattern. Climate change has the potential to increase the frequency and intensity of flooding and/or drought, both of which already cause severe hardship to communities in Cambodia.

According to UNDP statistics, 22,695 Cambodians out of every million were impacted by natural disasters in the country between 2005 and 2012, especially by flood and drought. With nearly 15 million living in the country, that leaves hundreds of thousands vulnerable to the changing climate. Flooding in 2009, 2011 and 2013 led to more than $1 billion in damage and 461 fatalities.

In 2015, Cambodia experienced its worst drought in half a century, with most of its 25 provinces experiencing water shortages, and about 2.5 million people severely affected. By early 2019 drought had affected more than 20,000 hectares of rice fields in 13 provinces, according to Cambodia’s National Committee for Disaster Management. That’s because a warmer world means a change in fundamental water cycles, including the monsoons, which are a major part of Cambodia’s annual farming routine. Climate research suggests that more countries can expect more droughts and more floods as this cycle changes. And because Cambodia has so little infrastructure and other mitigation methods, it has little means of moderating the impact of these changes. That puts Cambodia at the bottom of the Global Climate Risk Index, put together by Germanwatch, a think tank.

“In recent years, countries including Cambodia and Vietnam have regularly appeared in the bottom 10 list, and this year was no exception,” according to Germanwatch’s 2015 index. “Cambodia’s ranking is connected with 2013’s particularly sever monsoon season, which induced heavy rainfall and widespread flooding throughout a country that was still recovering from the damage of previous year’s floods.”

Cambodia maintains roughly 58 percent forest cover, compared with 73 percent prior to the civil war, which began in 1970, and is rich in biodiversity. It is home to the third-largest lowland dry evergreen forest in Southeast Asia, with 2,300 plant species, 14 endangered animals, and one of seven elephant corridors left in the world. However, only 24 percent of Cambodia’s land is protected. Threats to Cambodia’s forest landscapes and biodiversity include clearing and degradation, overexploitation of key species, and undervaluing of ecological services such as carbon sequestration. Industrialized agriculture and mine exploration continue to degrade forests significantly.

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Page last modified: 19-03-2019 09:53:22 ZULU