Analyzing Inter‐Hemispheric Climate Change Asymmetries With a Cointegrated Vector Autoregression

We study the heterogeneity in climate change patterns between hemispheres using a cointegrated vector autoregression (CVAR) derived from an energy balance model. We provide new estimates of the responses of hemispheric climate conditions to shocks in radiative forcing, indicating stronger responses of surface temperature in the Northern than in the Southern Hemisphere, and similar responses of ocean heat content. The difference in equilibrium climate sensitivity between hemispheres is estimated to be around 1.2°C and statistically significant. We also use the model to make projections of the inter-hemispheric difference in temperature anomalies, conditional on the scenarios of forcing considered by the Intergovernmental Panel on Climate Change. The projections range from 0.5°C to 2.1°C in 2100, depending on the scenario. Stochastic forecasts based on the estimated CVAR model are used to assess the probability of alternative scenarios. Possible economic implications of asymmetries are discussed.