Cointegration Analysis of Hemispheric Temperature Relations

In this paper, we use cointegration procedures to estimate a time series model of the relation among temperature and the radiative forcing of solar irradiance, greenhouse gases, and tropospheric sulfates. The results are consistent with some basic hypotheses regarding the effect of changes in radiative forcing on temperature and offer several lines of evidence that indicate human activity is partially responsible for the increase in temperature over the last 150 years. The same methods are applied to output from the SUL experiment run on the Hadley Centre climate model. Although we do identify a model that indicates a relation between the model data radiative forcing and the surface temperature, we cannot reject alternative specifications. The lack of a definitive results may be caused by important differences between the historical and SUL data. These differences are caused in part by smoothing techniques applied to the data for radiative forcing used to simulate the model and serve as a caution to those who use climate models to analyze the temporal relation between radiative forcing and temperature.