The Fed’s Climate Studies Are Full of Hot Air

One finds a correlation by assigning equal weight to all countries, from China to tiny St. Vincent

By David Barker. Mr. Barker runs a real-estate and finance company. He has taught economics and finance at the University of Chicago and the University of Iowa and worked as an economist at the Federal Reserve Bank of New York. He has a doctorate in economics from the University of Chicago. Excerpts:

"I took a close look at two Fed studies on the subject and found shockingly poor analysis. These studies on the effect of temperature on U.S. and world economic growth are cited without a hint of skepticism and widely lavished with media attention. I’ve managed to debunk both. 

In the September issue of Econ Journal Watch, I discredited a paper from the Richmond Fed claiming that warming reduces economic growth in the U.S. I showed that the paper had serious problems with its statistical reasoning and robustness. My analysis concluded that the data used in the paper showed no meaningful relationship between temperatures and growth.  

More recently I published a critique of a study from the Federal Reserve Board claiming that a year of above-normal temperatures in countries around the world makes economic contraction more likely. The original study used sophisticated statistical techniques but failed to report that its primary finding was statistically insignificant. My request to the study’s author for computer code to reproduce the paper’s results went unanswered. 

I managed to write the code from scratch and exactly replicate the results, allowing me to run additional tests that the author didn’t report. The author’s primary result—that temperature has a bigger effect in bad than in good economic times—turned out to be statistically insignificant. Additional analysis showed that there is no reliable effect of temperature on growth at all.

There are two main reasons why the Fed study appeared at first to show a statistically significant effect of temperatures on economic growth. First, each country in the sample had equal weight in the analysis. China had the same weight as St. Vincent though China’s population is 13,000 times as large. Equal weighting means that some small countries with unusual histories of economic growth greatly influenced the results.

The paper’s results disappeared when countries like Rwanda and Equatorial Guinea—which had economic catastrophes and bonanzas unrelated to climate change—were omitted. Omitting similar countries representing less than 1% of world gross domestic product was enough to eliminate the paper’s result. The complicated statistical techniques used in the Fed study magnified the influence of these unusual countries.

There’s a second reason why the Fed study appears to find that temperature affects growth: Many poor countries have warm climates. A warm climate doesn’t preclude economic growth, as is demonstrated by Florida, Arizona, Taiwan, Singapore and several Persian Gulf states. But the average poor country is warmer than the average rich country. Debate continues as to whether this correlation is random or causal, but the hypothesis of the Fed paper is that year-to-year increases in temperature reduce annual economic growth. The paper claims that its method controls for long-term differences in climate, but using simulated data I found that the Fed paper’s method can be fooled into finding an effect that doesn’t exist."