Role of the natural and anthropogenic radiative forcings in global warming: evidence from cointegration-VECM analysis

Over the last few years there has been much debate about the hypothe- sis that anthropogenic emissions of CO2 and other greenhouse gases increase global temperature permanently. By using recent advances in time series econometrics, this paper tries to answer the question on how human activity affects Earth’s surface tem- peratures. Bearing in mind this goal, we estimated the long-run cointegration relations between global temperatures and changes in radiative forcings by a set of perturbing factors. We found that the temperature response to a doubling in radiative forcing of anthropogenic greenhouse gases is +2.94 °C [95% CI : +1.91, + 3.97], in perfect accordance with prior research), and that the orthogonalized cumulated effect over a 100 year time period, in response to a unit increase of size of one standard de- viation in greenhouse gas radiative forcing, is +3.86 °C [95% CI : +0.03, + 6.54]. Conversely, the amplitude of solar irradiance variability is hardly sufficient to explain observed variations in the Earth’s climate. Our results show that the combined effect of stochastic trends attributable to anthropogenic radiative forcing variations are driving the Earth’s climate system toward an ongoing phase of global warming, and that such long-run movement is unlikely to be transient.