A new study from Stanford University says global warming has increased the wealth gap between the world’s countries by enriching cooler, wealthier countries and dragging down growth in hotter, poorer countries.
The study found that “most of the poorest countries on Earth are considerably poorer than they would have been without global warming,” climate scientist Noah Diffenbaugh, lead author of the study, said in a statement from Stanford.
The study, which looked at the period from 1961 to 2010, was published Monday in the Proceedings of the National Academy of Sciences. It was co-authored by Marshall Burke, a Stanford assistant professor of Earth system science.
Overall income disparity between countries has dropped in recent decades, but the gap would have narrowed faster without climate change, the study found.
Burke and co-authors had previously looked at the records of annual temperature and GDP measurements for 165 countries to estimate the effects of temperature changes on economic growth.
“The historical data clearly show that crops are more productive, people are healthier and we are more productive at work when temperatures are neither too hot nor too cold,” Burke said in the statement. “This means that in cold countries, a little bit of warming can help. The opposite is true in places that are already hot.”
In the new study, the researchers combined their previous work with data from more than 20 climate models developed around the world. Researchers used the models to figure out how much each country had warmed over the period, and then, after thousands of simulations, determined what the country’s economic output would have been if the temperatures had not warmed, the statement said.
Burke said that as far as tropical countries go, “There’s essentially no uncertainty that they’ve been harmed” by the increasing heat.
Diffenbaugh noted in a telephone interview that there was less confidence about the beneficial economic effect of global warming on cooler countries. “That’s a less robust result than the negative impact,” he said.
Countries in the mid-latitudes, including the United States, haven’t seen as large an effect, but that could change if there’s a large amount of warming in the future, Burke warned in the statement.
“A few of the largest economies are near the perfect temperature for economic output. Global warming hasn’t pushed them off the top of the hill, and in many cases, it has pushed them toward it,” Burke said. “But a large amount of warming in the future will push them further and further from the temperature optimum.”
Here are some examples of what the researchers found in terms of the difference between what their economic growth could have been and where they actually were in 2010, in terms of per capita gross domestic product:
Countries whose economies were harmed by the warming
Sudan (population 41 million): -36 percent
India (population 1.3 billion): -31 percent
Nigeria (population 191 million): -29 percent
Indonesia (population 264 million): -27 percent
Brazil (population 209 million): -25 percent
Countries who were helped by the warming
Norway (population 5 million): +34 percent
Canada (population 37 million): +32 percent
Sweden (population 10 million): +25 percent
Great Britain (population 66 million): +9.5 percent
France (population 67 million): +4.8 percent
The countries with the three biggest economies
USA (population 327 million): -0.2 percent
China (population 1.4 billion): -1.4 percent
Japan (population 127 million): -1.1 percent
Diffenbaugh said that the study also offered looked at how much each country had been affected economically by global warming, relative to its historical greenhouse gas contributions.
“Our results show that, in addition to not sharing equally in the direct benefits of fossil fuel use, many poor countries have been significantly harmed by the warming arising from wealthy countries’ energy consumption,” the study said.