The global climate system is exceedingly complex. Every year, new reports force us to rethink our existing climate knowledge. The United Nations recently found that, even if countries meet their Paris Agreement targets, the Arctic could still warm nine degrees Celsius by 2100.
Climate change is already happening. Though we will likely never be able to quantify all the ways that climate change has affected our lives—and, indeed, it's all probably worse than we think—researchers at Stanford University recently quantified the extent to which global warming has already slowed the economic growth of warmer countries, thereby making it harder to close the global wealth gap.
Using historical data, the researchers report that, "although between-country inequality has decreased over the past half-century, there is a 90 percent likelihood that global warming has slowed that decrease." Hot days already decrease productivity in poorer, hotter countries, but when exacerbated by anthropogenic global warming, that effect becomes more pronounced, the team has found. Meanwhile, they report that the richer, more temperate countries, which are causing most of the warming, have gotten off scot-free in an economic sense—and may even be benefiting from the warming.
Noah Diffenbaugh, one of the authors of the recent Stanford study, spoke with Pacific Standard about how climate change has exacerbated global inequality, and how we can stop that vicious cycle.
What are the main takeaways from your study on climate change and global inequality?
In this study, we're bringing together two existing research threads. One is what my co-author, Marshall Burke, has been working on for a number of years: quantifying the empirical relationship between temperature fluctuations and economic growth. So what [Burke's calculations] find is this parabolic relationship, where cold countries tend to have a bit faster economic growth in warm years, whereas some countries on the other side of the hill, on the downward part of the parabola, tend to have slower economic growth in warm years. That econometric relationship has been used to project future damages from further global warming.
What we did in this analysis is to combine that econometric analysis with multiple climate models to run the experiment of what the climate would have been like without human emission of greenhouse gases and aerosols. Those climate models are used to generate the counterfactual hypothesis of what the climate of the world would have been without humans. For each country, we run more than 20,000 realizations of what its economic trajectory would have been without global warming. And then we use that large set of counterfactual realizations to calculate the uncertainty in each country, and for inequality across the world.
What's the significance of using historical data only, instead of projected impacts?
We've now had a degree Celsius of global warming over the last century or so, and we're already experiencing impacts from that global warming. It's frequently stated that the countries and populations that are most vulnerable to climate change are also least responsible for contributing to global warming, but it has not yet been quantified exactly what the economic impact in each country has been.
There have been quite a bit of analyses trying to quantify the likely economic damages from future global warming and different levels of future global warming. Marshall Burke and I had a paper in Nature last year conducting that quantification for the United Nations' Paris targets, to calculate the differences in economic damages between targets and what their likelihoods are.
You conclude that increasing the use of low-carbon energy sources would help remove some hindrances to growth in poorer countries. How would that happen?
Lack of energy resources is a major impediment to economic development. Regardless of the source of the energy, whether the electricity is being generated by combusting coal or by wind farms, the most important benefit is the access to electricity.
The argument we're making is that, because warming has already slowed economic growth in countries that are not only warm, but also, in many cases, have large poor populations [and] low access to energy resources, further warming is highly likely to increase further burdens on economic growth. Increasing energy access through technologies that do not increase warming as much as fossil fuels [do] would have a secondary benefit of decreasing this drag on economic growth that comes from the warming. To be clear, the primary benefit is access to energy, regardless of the energy source, but if that energy source doesn't create further global warming, then that will provide a secondary benefit by decreasing this drag on economic growth.
These findings confirm that global warming is driving global inequality, which is something we've known for a while. How does your study build on previous research?
The countries and populations that are most vulnerable to climate change have contributed relatively little to the cause of climate change, in terms of greenhouse gas emissions. So this is not a new concept. What our study does provide is the first country-level specific quantification of the economic impact of the historical global warming that's already happened.