A new study has established a clear link between climate change and the worsening income inequality plaguing the developing nations of the world.

It says warmer temperatures are widening the gap separating richer and poorer countries and effectively boosting the economies of many wealthy polluters while dampening growth in much of the developing world.

The published study by Stanford University in Palo Alto shows that inequality between the haves and have-nots is already 25 percent greater than it would be in a cooler world. It builds on previous research that found economic activity peaks at an average temperature of 13 degrees Celsius.

This “Goldilocks” condition means it’s neither too hot nor too cold for prosperous economic activity. On the other hand, lower temperatures can damage weather-dependent sectors like agriculture while hotter temperatures can destroy crops, sap workers’ energy and worsen social conflicts.

Climate scientist and study authors Noah Diffenbaugh and economist Marshall Burke, both at Stanford, used climate and economic models to reveal the economic impacts of climate change country by country, starting in 1961.

Their model compared how each country performed in hotter and colder years. At the same time, they accounted for other factors such as technological innovations and the ups and downs in the global economy.

Diffenbaugh and Burke created two “worlds” based on each country’s response to temperatures. One world reflected actual global warming and another without greenhouse gas (GhG) pollution.

Comparing them showed that between 1961 and 2010, many countries near the Equator (generally poorer) lost an average of more than 25 percent of potential growth in gross domestic product (GDP) because of global warming.

In contrast, many cooler, mostly wealthier countries enjoyed an economic boost of 20 percent or more, thanks to warmer weather. Since 1961, for example, Norway’s per capita GDP grew an extra 34 percent while India lost almost the same total.

“Even small changes in the growth rate compound over time and you can see big effects,” Burke said.

From 1961 to 2010, the median economic losses in countries closer to the equator including parts of South America, central Africa, and South East Asia were 25 percent greater than they would have been in a world without global warming, according to the study.

The negative economic impact, measured in per capita GDP, was 31 percent for India, 29 percent for Nigeria and 25 percent for Brazil. The countries that have become richer due to global warming include Canada, which experienced a 32 percent increase in per capita GDP, and Norway with a 34 percent increase, relative to a world without climate change.

Some other countries including China and the U.S. registered very little change in GDP due to climate change over the half century.

Another study published in 2017 showed the U.S. economy will lose some 1.2 percent of GDP with a 1 degrees Celsius increase in average temperatures.

Burke acknowledged that more complete economic data could make for more certainty. But he defends the results as “the best possible interpretation of the data.”

He also said they could feed discussions about whether richer nations responsible for the lion’s share of historic emissions should compensate poorer nations for climate damage.

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