"This is a substantial sum but the economic returns from adopting low-carbon policies far outweigh the costs," Juzhong Zhuang, ADB's deputy chief economist, said. "The region can generate more than $2 in gains for each $1 of cost it bears to reach the Paris goal—if the right steps are taken."
Reduced investment in fossil fuel extraction could also help offset 20 percent of the total costs, the report said.
In December, global governments pledged to mitigate greenhouse gas emissions in order to keep average temperature increases below 2 degrees Celsius.
The ADB's developing member countries—which include the bulk of Asia, with the exception of Japan—are among the main players in global climate change. Three of the region's most populous economies, China, India and Indonesia, ranked among the top five greenhouse gas emitters in 2015, according to the World Resources Institute.
"If uncontrolled, climate change may lead to economic losses equivalent to 10 percent of gross domestic product (GDP) in 2100, reversing many hard-won socioeconomic gains in the region," the ADB report cautioned.
But it was not just GDP losses at stake, according to the report.
The $300 billion annual spend on green infrastructure, including renewable power, smart grids and energy storage, could lead to improved air quality and preserve more than 45 million hectares of forest, the ADB said.
Air pollution is the fourth-highest risk factor for deaths worldwide, according to the World Bank. And Southeast Asia boasts a higher deforestation rate than any other major tropical region, the ADB noted.