The influence of solar changes on decadal-to-millennial scale climate variability is a matter of some dispute. In a previous study the PIs correlated atmospheric 14C records with a number of different indices of climate and found that the correspondence was quite weak for many records. However, the correlation was significantly higher for one record in China, and other studies continue to provide some support for a sun-climate connection. The PIs therefore believe it is appropriate to suggest a sun-climate connection that may be statistically significant, but at the same time contributes only a modest amount of the variance to centennial-scale climate change. Viewed from this perspective, several objectives for further work suggest themselves; expanded analysis of climate records in order to more systematically examine the sun-climate connection, with special emphasis on trying to determine the amount of variance explained by any significant correlations, and whether there is some larger-scale coherence to regions of poor or good correlation. It is also necessary to determine whether the proposed sensitivity of the climate system on centennial-time scales is consistent with both solar and climate models. The PIs therefore specifically propose the following: (1) refined statistical analyses of a greater number of paleoclimate records, including climate correlations with both 14C and 10Be solar indices; and (2) modeling the geographic response to periodic solar constant variations. This research should help clarify the significance of a sun-climate connection, and perhaps why some records seem to show a connection while others do not.
