The physical structure of the oceans and atmosphere entails very long equilibrium dynamics due the slow accumulation of heat in the land and ocean. An ARMA analysis evaluates the potential of accumulation of solar anomaly to explain the global temperature changes over glacial/interglacial and recent time-frames.
Click image above for animation of the accumulation model for the 1950-2011 period.
The results of an early version of the accumulation theory are here.
Contrary to the consensus view, the historic temperature data displays high sensitivity (x10 gain) to solar variations when related by slow equilibration dynamics. A variety of results suggest that inappropriate specification of the relationship between forcing and temperature may be responsible for previous studies finding low correlations of solar variation to temperature. The accumulation model is a feasible alternative mechanism for explaining both paleoclimatic temperature variability and contemporary warming without recourse to increases in heat-trapping gases produced by human activities.
There are no valid grounds to dismiss the potential domination of 20th century warming by solar variations.
UPDATE: David Hagen alerted me to a post at WUWT where sun-spots were accumulated from 1500.
The sunspot record needs to be examined in its entirety rather than as individual sunspot cycles. The method to do this is by calculating the accumulated departure from the average of all the sunspot numbers of the entire 500-year index. This reveals the cooling during the Maunder Minimum and the current “global warming”. The current warming of 15 watts per square meter began in 1935, based on the sunspot record.