The Income-Temperature Relationship in a Cross-Section of Countries and its Implications for Predicting the Effects of Global Warming.

Hotter countries are poorer on average. This paper attempts to separate the historical and contemporaneous components of this income-temperature relationship. Following ideas by Acemoglu et al. (Am Econ Rev 91(5):1369-1401, 2001), we use colonial mortality data to account for the historical role of temperature since colonial mortality was highly correlated with countries' average temperatures. The remaining income-temperature gradient, after colonial mortality is accounted for, is most likely contemporaneous. This contemporaneous effect can be used to estimate the consequences of global warming. We predict that a 1°C temperature increase across all countries will cause a decrease of 3.8% in world GDP. This prediction is robust across functional forms and an alternative method for separating historical effects.