No matter how it is measured, income declines with global warming

The contemporaneous relationship between temperature and income is important because it enables economists to estimate the economic impact of global warming without assuming a structural model. Until recently, empirical evidence generally suggests that there is a negative relationship between temperature and income, and, therefore, global warming has an adverse impact on economic activity. However, Nordhaus (2006) argues that the temperature-income relationship depends on how income is measured. We show in this paper that the results of Nordhaus (2006) may be due to an omitted-variable problem. Based on a well-motivated temperature-income model, we find that the relationship between temperature and income is not dependent on income measurement. Our regression results show that the adverse impact of an increase of 1. °C in temperature can be as much as a 3% decrease in total income for the G-7 nations. Therefore, our results suggest an aggressive climate mitigation policy.