Thirty Year Climate Forecast
..The geologic record shows clearly that the sun is the main climate driver. The Milankovitch multi-millennial orbital cycles in NH insulation are firmly established in the record as are the Schwab and deVries cycles. Other millennial and decadal variations in solar activity are present in the record. TSI is not the only or even the best indicator of solar activity - variations in EUV radiation and the GCR flux (via cloud formation and earth's albedo) seem to be more important on decadal and centennial scales . Earth's climate is the result of complex resonances between all these solar cycles with the lunar declination cycles and endogenous earth processes.
At this time the sun has entered a quiet phase with a dramatic drop in solar magnetic field strength since 2004. This suggests the probability of a cooling phase on earth and it seems possible that Cycle 23 is more or less equivalent to Cycle 4 so that a Dalton type minimum is likely.
It is now clear that the patterns of the earth's ocean and atmospheric current systems provide the most immediate guide to the current state of the climate when climate is considered as the result of the complex processes discussed above and these systems provide the best clues as to likely developments over the next 20 - 30 years. Beyond that time span predictions are currently of little practical value. The small effect of anthropogenic CO2 cannot be calculated with any useful accuracy until we can better quantify the effect of the natural variations.