Australia: The Land Where Time Began

A biography of the Australian continent 

Cause of Decoupling Between Solar Radiation and Temperature - the Evidence

Throughout the Holocene the Sun has been a major external forcing to the climate system, but in the last few decades opposite trends have been identified empirically The authors¹ used the Granger causality analysis, an inferential method, to analyse this situation their results showing for the first time that there has evidently been a causal decoupling between solar irradiance and global temperature that has been apparent since the 1960s.

It has been indicated by a number of studies, that the Sun major role throughout the Holocene in contributing to the driving of the climate (cf. Jansen et al., 2007+refs). It has been found by more recent studies using simple correlation and graphical methods that a behaviour that is contrary is evident when compared with the trend in temperatures since the 1980s (Lockwood & Fröhlich, 2007; Stauning, 2011). 

According to the authors¹ it therefore appears there has been a decoupling between recent temperature behaviour and solar forcing, leading to their asking of the question, is the decoupling causal? If this is the case another question arises, when did the solar radiation lose its importance as an influence on temperature? In this paper the authors¹ use an inferential method, the Granger causality analysis, to address these problems.

A number of studies have applied this method to specific climate system problems (Diks & Mudelsee, 2000; Kaufmann et al., 2003; Elsner, 2006, 2007;  Kaufmann et al., 2007; Mohkov et al., 2011). Other studies have applied the method to climate attribution (Sun & Wang, 1996; Kaufmann & Stern, 1997; Reichel et al, 2001; Triacca, 2001, 2005; Mohkov & Smirnov, 2008; Kodra et al, 2011; Attanasio et al, 2012).

See Source 1

The authors¹ say they are aware that Granger causality is 1 of a number of possible definitions of causality, and as Granger causality is based upon precedence and predictability it can be considered to be a tool that is helpful in determining the causality direction.

Conclusion

According to the authors¹ they have shown that in recent periods, between total solar radiance and global temperature there is an evident causal decoupling. The results of their study indicate that the loss of importance of solar influence on temperature occurred in the 1960s; the same time that the total radiative forcing due to greenhouse gases has shown a strong Granger link with temperature between the 1940s and the present.

The authors say it is obvious the results of their study suggest further research is required to extend their work to greater depth regarding the decoupling of the Sun-temperature relationship, though the results appear to be a clear contribution to the debate on the causes of the present global warming.

Sources & Further reading

1. Pasini, Antonello, Umberto Triacca, and Alessandro Attanasio. "Evidence of Recent Causal Decoupling between Solar Radiation and Global Temperature." Environmental Research Letters 7, no. 3 (2012): 034020.