In another section of his recent “trip report ” (see “westling” post below), James Hansen, head of the NASA Goddard Institute for Space Studies, answers in careful but fairly accessible detail, the question of whether the sun can reasonably be blamed for recent global warming.
Thus if the sun remains “out”, i.e., stuck for a long period in the current solar minimum, it can offset only about 7 years of CO2 increase. The human-made greenhouse gas climate forcing is now relentlessly, monotonically, increasing at a rate that overwhelms variability of natural climate forcings. Unforced variability of global temperature is great, as shown in Figure 4, but the global temperature trend on decadal and longer time scales is now determined by the larger human-made climate forcing. Speculation that we may have entered a solar-driven long-term cooling trend must be dismissed as a pipe-dream.