By Marc Jones

LONDON, (Reuters) – Climate change could result in a loss of 4% global economic output by 2050. This would be devastating for many of the poorest parts of the globe. A new survey of 135 countries estimates that this is what climate change will do.

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 continue to avoid major changes in climate policy – referred to as RCP 4.5 by researchers – then countries with lower incomes will see an average of 3.6 times more gross domestic product loss than the ones who are richer.

South Asia is at 10%-18% risk from floods and wildfires in Bangladesh, India and Pakistan, as well as water shortages. This is roughly 10x the amount of Europe and North America’s most affected region.

Sub-Saharan Africa region, Central Asia, North Africa, and Middle East are all at risk. Sub-Saharan Africa is also vulnerable to East Asia and Pacific nations, though this exposure is more due to floods and storms than drought and heat waves.

“To different degrees, this is an issue for the world,” said S&P’s top government credit analyst, Roberto Sifon-Arevalo. One thing that stands out to me is the urgent need for international assistance for these poorer parts of the globe.

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

Smaller islands or countries near the Equator tend to be at greater risk. However, economies that are heavily dependent on agricultural sectors will be less affected than those that have large service sectors.

The cost of climate change is increasing for most countries. According to Swiss Re, the losses from climate change have been around 0.3% per annum over the last 10 years.

According to the World Meteorological Organization, (WMO), there have been 115 deaths per day and more than $202 million losses in weather-related disasters over the past 50 years.

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.

He said that the data would not be integrated into their sovereign rating models as they were too uncertain about how the countries will adapt.

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 stated, “We try to tell what’s relevant and where.” “But, we don’t rate to the worst-case scenarios. We rate to the base-case scenarios.”