Global warming will harm sovereign creditworthiness around the world this century, with poorer nations the worst hit, Standard & Poor’s Ratings Services said.

Climate change is one of two “global mega-trends” alongside aging populations that dominate global economic risks, the agency said in a report. It identified the most vulnerable nations as Vietnam, Bangladesh and Senegal. Luxembourg, Switzerland and Austria were deemed least at risk.

Global warming “will put downward pressure on sovereign ratings during the remainder of this century,” S&P analysts led by Moritz Kraemer in Frankfurt wrote. “The degree to which individual countries and societies are going to be affected by warming and changing weather patterns depends largely on actions undertaken by other, often far-away societies.”

Temperatures have warmed by about 0.85 degree Celsius since 1880 and are likely to warm by another 0.3 to 4.8 degrees by 2100, according to the United Nations. U.N. scientists warned in March that the world is ill-equipped to deal with impacts of warming such as melting glaciers, rising sea levels and more prolonged droughts.

While extreme weather events such as tropical storms and floods appear to have been increasing in frequency since the 1980s, S&P said it has so far not revised any country’s credit rating as a result. Unlike aging, there’s insufficient reliable data to make accurate predictions, heightening the unpredictability caused by rising temperatures, the report said.

“However, assuming that extreme weather events are on the rise in terms of frequency and destruction, how this trend could feed through to our ratings on sovereign states bears consideration,” the analysts wrote.

Changing rainfall patterns could affect agricultural yields, and altered weather could spread disease and pests, hitting productivity, they said.

The agency devised a “crude” ranking of 116 nations according to their vulnerability across three indicators: proportion of population living lower than 5 meters above sea-level, share of agriculture in economic output and a vulnerability index compiled by Notre Dame University.

Vietnam, Bangladesh and Senegal were followed in the vulnerability ranking by Mozambique, Fiji, the Philippines, Nigeria, Cameroon, Papua New Guinea and Indonesia.

“Unlike in the case of aging, individual societies cannot by themselves meaningfully reduce the impact they will feel as the climate changes,” the analysts said. “A society may choose to reduce its carbon emissions unilaterally to reduce the risk of the potential consequences of global warming, but due to the global character most of the benefits of that society’s sacrifice will accrue to other nations.” (Bloomberg)