Using models based on Britain's 2006 Stern Review, the ADB predicts that the cost of inaction on climate change could reach 6.7 percent of economic output by 2100 in Indonesia, Thailand, Vietnam, and the Philippines. This outstrips a global loss of 2.6 percent using the same scenario. It includes potential losses from weather events like typhoons and floods, as well as the cost of relocating millions of vulnerable people.
A warmer climate also poses unexpected challenges to health authorities, as the peak period for mosquito-borne diseases is extended. For vulnerable communities, shifts in such outbreaks go hand in hand with increased flooding, violent storms, and other climate-driven threats.
"It's very obvious when a cyclone hits you…. It's much harder for the collective consciousness to grapple with the idea that there is a changing pattern of disease in a city," says Ashvin Dayal, managing director in Asia for the New York-based Rockefeller Foundation, which is funding adaptation projects in six cities in Vietnam and India as part of a five-year, $70 million program.
Scientists generally agree that global temperatures will continue to rise, even if efforts to cap greenhouse-gas emissions bear fruit. But forecasting exact temperatures and how they affect various ecosystems is complex. Moreover, climatologists say that monsoon patterns are equally, if not more, crucial to farmers in regions like Southeast Asia.
The ADB predicts that Indonesia, Thailand, and Vietnam will face drier conditions over the next two to three decades, before the pattern reverses mid-century and brings more rainfall. By contrast, the Philippines should expect increasing precipitation. Using a 1990 baseline and a high-emissions scenario, annual temperatures in the four countries by 2100 could rise by 4.8 degrees C., as hot seasons become even hotter, putting greater stress on water resources.