PHNOM PENH, June 5 (Xinhua) -- If the global rise in temperatures is kept below 2 degree Celsius by 2100 and Cambodia maintains current levels of investment in climate change adaptation, climate change will reduce Cambodia's GDP by 9.8 percent in 2050, the United Nations Development Program (UNDP) said on Tuesday.

The UN agency said in a statement that reduced labor productivity - caused by workers slowing down or becoming fatigued due to higher temperatures - will be the main cause of GDP loss, accounting for 57 percent of the economic loss and damage caused by climate change in the country in 2050, citing a macro-economic report titled "Cambodia Climate Economic Growth Impact Model."

The report was prepared by the Ministry of Economy and Finance and the National Council for Sustainable Development with technical support from the UNDP.

This GDP loss is significantly higher than previous modelling work done in Southeast Asia, the statement said, adding that much of the focus of climate change spending has been on mitigation and adaptation measures in relation to natural disasters, but rising temperatures pose a bigger threat when it comes to the economic impact of climate change in Cambodia.

Nick Beresford, UNDP country director for Cambodia, said that in Cambodia, sectors such as construction, manufacturing and agriculture accounted for 52 percent of GDP in 2016 and 75 percent of the employed population in 2013.

"Current adaptation activities underestimate the importance of heat stress on these industries where air-conditioning is a rarity and workers are highly vulnerable," he said.

He added that more research needs to be done on ways to protect supply chains and workers from heat stress.

Cambodia's GDP in 2015 was already 4.6 percent lower than it would have been without climate change over the 1993-2015 period, the statement said.

The report, which is the first of its kind, was launched by the Ministry of Economy and Finance on April 27.

"The ministry will be able to use the results to inform the new five-year development strategy, budget priorities and policy reforms for Government," said Ros Seilava, undersecretary of state of the Ministry of Economy and Finance, in his remarks at the launch.

Tin Ponlok, secretary general of the National Council for Sustainable Development, said the methodology was fully transparent, using existing climate change macro-economic models and simplifying them.

"It integrates local evidence and case studies on the impacts of climate change, and has been calibrated using national data and interviews in key sectors," he said.

Results indicate that additional research and evidence is needed on the impacts of high levels of heat in various working conditions so that new technological solutions and labor regulations can be put in place to protect workers and the economy, the release said.

The report concluded that, if maintained, current levels of spending on adaptation in Cambodia would help to avoid 33 percent of impact by 2050, but that strengthened policies could help avoid up to 66 percent.