Since the discovery of a striking correlation between 1-2-2-2-1 filtered solar cycle lengths and the 11-year running average of Northern Hemisphere land air temperatures there have been widespread speculations as to whether these findings would rule out any significant contributions to global warming from the enhanced concentrations of greenhouse gases. The "solar hypothesis" claims that solar activity causes a significant component of the global mean temperature to vary in phase opposite to the filtered solar cycle lengths. In an earlier paper we have demonstrated that for data covering the period 1860-1980 the solar hypothesis does not rule out any significant contribution from man-made greenhouse gases and sulphate aerosols. The present analysis goes a step further. We analyse the period 1579-1987 and find that the solar hypothesis - instead of contradicting - appears to support the assumption of a significant warming due to human activities. We have tentatively "corrected" the historical Northern Hemisphere land air temperature anomalies by removing the assumed effects of human activities. These are represented by Northern Hemisphere land air temperature anomalies calculated as the contributions from man-made greenhouse gases and sulphate aerosols by using an upwelling diffusion-energy balance model similar to the model of Wigley and Raper employed in the Second Assessment Report of The Intergovernmental Panel on Climate Change. It turns out that the agreement of the filtered solar cycle lengths with the "corrected" temperature anomalies is substantially better than with the historical anomalies. Therefore our findings support a total reversal of the common assumption that a verification of the solar hypothesis would challenge the IPCC assessment of man-made global warming.
|Journal||Journal of Atmospheric and Solar-Terrestrial Physics|
|Publication status||Published - 1999|