Human Activities and Global Warming: A Cointegration Analysis

Do human activities indeed cause global warming? This paper attempts to answer this question by reexamining the time series properties of climate variables and the existence of long-run relationships between them. Double unit root testing shows that most of the radiative forcings of greenhouse gases are integrated of order two. We then apply an I(1) and I(2) cointegrating rank analysis to identify the presence of I(2) components. After identifying a linear combination of I(2) variables that cointegrates to an I(1) process, we proceed with the I(1) cointegrating analysis and we identify two possible cases with different rank specifications. Estimation of the equation for temperature suggests that this variable reacts significantly to the radiative forcings of greenhouse gases in the long-run. This evidence allow us to conclude that human activities affect temperature variations.