A rising tide may lift all boats. But when it comes to economic prosperity, the same can't be said for rising temperatures.
That's the conclusion of a new study that looks at the gap between the world's richest and poorest nations, and determines that the gap would be smaller without anthropogenic climate change.
"We find that global warming has very likely exacerbated global inequality," Stanford University researchers Noah Diffenbaugh and Marshall Burke write in the Proceedings of the National Academy of Sciences.
"Although there is uncertainty in whether historical warming has benefited some temperate, rich countries, for most poor countries there is a 90 percent likelihood that per capita gross domestic product (GDP) is lower today than if global warming had not occurred."
GDP, one of the primary indicators used to measure the health of a nation's economy, is the value of all goods and services provided within the nation during a given year.
The researchers took climate model simulations that are normally used to predict future conditions and instead used them to estimate what today's global economy would look like if the world had not been heating up for the past half-century. The team utilized "empirical evidence of the relationship between historical temperature fluctuations and economic growth."
That includes Burke's 2015 study, which found that the relationship between temperature and economic output is surprisingly straightforward. He reported that productivity peaks "at an annual average temperature of 13 degrees Celsius (55 degrees Fahrenheit), and declin[es] strongly at higher temperatures. This relationship is globally generalizable, unchanged since 1960, and apparent for agricultural and non-agricultural activity in both rich and poor countries."
This new research suggests that a loss of productivity substantially hurts the economies of poorer, warmer nations, which tend to be closer to the equator than richer ones.
"Although between-country inequality has decreased over the past half-century, there is a 90 percent likelihood that global warming has slowed that decrease," they conclude. "Over the course of decades, [climate change] has accumulated robust and substantial declines in economic output in hotter, poorer countries—and increases in many cooler, wealthier countries—relative to a world without anthropogenic warming."
The potentially positive take on these findings is that slowing climate change by moving to more sustainable energy sources could decrease the worldwide wealth gap. But that's not much of a call to arms for residents of richer nations, who might not want to give up the economic advantages they've long enjoyed.
Perhaps a more persuasive argument is that climate change is already creating economic refugees—the exodus of Central Americans to the southern United States border is partially due to the phenomenon—and many, many more are likely to migrate in the decades to come. This latest research suggests that limiting global warming could help protect migrants' home economies from deteriorating, giving them less incentive to emigrate to more prosperous nations.
Build wind turbines today, and you may not need to build walls tomorrow.