By Marc Jones

LONDON, (Reuters) – Climate change could result in 4% global economic output being lost by 2050. This would be disproportionately devastating many parts of the globe that are poorer than others. A new survey of 135 countries estimates this.

Ratings firm S&P Global (NYSE:), which gives countries credit scores based on the health of their economies, published a report on Tuesday looking at the likely impact of rising sea levels, and more regular heat waves, droughts and storms.

If governments tend to avoid major changes in climate policy – referred to as RCP 4.5 by researchers – then countries with lower incomes and higher average GDP losses will experience 3.6 times more than the richer.

South Asia is at 10%-18% risk from floods, wildfires, and major storms. This includes Sri Lanka, Pakistan, India and Pakistan. Its GDP also faces risks in Sri Lanka, Bangladesh and India.

Sub-Saharan Africa region, Central Asia, North Africa, and Middle East are all at risk. Sub-Saharan Africa’s exposure to East Asia, Pacific and other countries is similar. This is mainly due to flooding and hurricanes more than heat waves or drought.

“To different degrees, this is an issue for the world,” said S&P’s top government credit analyst, Roberto Sifon-Arevalo. The need to provide international assistance for the poorest parts of the planet is what really stands out.

GRAPHIC: Regions being hit hardest by climate change (https://fingfx.thomsonreuters.com/gfx/mkt/zjpqkmydxpx/Pasted%20image%201651013882764.png)

Countries near the equator and small islands are most at risk. However, economies heavily dependent on agricultural sectors will be less affected than those that depend more heavily upon services.

Most countries are now more exposed to climate change, with rising costs. Globally, losses due to storms, wildfires and floods have reached 0.3% of the GDP over the past 10 year according to Swiss Re (OTC).

World Meteorological Organization(WMO) calculates that every 50 years there has been an average of one weather, climate or water-related catastrophe. This means that 115 people have died and $202 millions in losses each day.

S&P’s Sifon-Arevalo said that some countries have already suffered credit ratings downgrades due to extreme weather, such as some Caribbean Islands after major hurricanes.

However, he stated that the updated data wasn’t going to be used in the firm’s sovereign ratings models because there was still uncertainty about the future.

A study https://www.reuters.com/article/us-climate-change-ratings-idUSKBN2BA2XW last year by a group of UK universities looking at a more extreme rise in global temperatures, predicted that over 60 countries could see their ratings cut because of global warming by 2030.

A sliding scale in rating system has also been suggested by experts. This would allow highly-exposed countries to have one credit score for 10 years, and then another for later when there are more likely to be problems.

Sifon Arevalo explained that “we strive to determine what is relevant, and where.” “But, we don’t rate to the worst-case scenarios. We rate to the base-case scenarios.”