Just when you thought the news about climate change couldn’t get any worse, consider this.

Not only will global warming put a massive dent in the world’s GDP over the coming decades, but it “is essentially a massive transfer of value from the hot parts of the world to the cooler parts of the world,” according to a new study in Nature. “This is like taking from the poor and giving to the rich.”

Researchers Stanford University analyzed 166 countries over a 50-year period (from 1960 to 2010) and compared economic output when country’s experienced normal temperature to abnormally cold or warm temperatures. Controlling for factors such as geography, economic changes, and global trade shifts, they found the optimum temperature where humans are good at producing stuff: 55ºF (13ºC).

Applying this finding to climate change forecasts, they found that 77% of countries will experience a decline in per capita incomes by 2099, with the average person’s income shrinking by 23%. Unusually high temperatures will hurt agriculture, economic production, and overall health, researchers say.

Stanford

However, some cold countries will benefit hugely, including Mongolia, Finland, Iceland, and Canada. Most European countries will see slight economic gains.

The Middle East, Africa, Asia and South America, where the world’s poorest are concentrated, are expected to be hit hardest by climate change. These countries are either already at or passed the economic Goldilocks temperature, so productivity will only fall as temperatures increase.

By showing how future climate change will cost the global economy, researchers hope policymakers will significantly invest in reducing emissions. World leaders are set to convene in Paris to negotiate an international climate treaty next month. Many have promised to cut emissions, but environmentalists have warned that current pledges aren’t enough to mitigate the worst-case scenario.