Moreover, we caution that the shifts described here are presumably superimposed upon a long term warming trend due to anthropogenic forcing.

Mojib Latif has made similar arguments when discussing current GWMs inaccuracy at the decadal time scale. I wonder why no one has stepped forward to point out that a superpositional decomposition of this sort is completely invalid for the analysis of coupled non-linear, time-variant systems such as global climate dynamics. One simply can not separate “natural variations” from anthropogenic forcing in a system whose feedback sensitivities are functions of the output state, a fact easily provable and taught in every first year physics curriculum. Superposition only applies to linear, time-invariant (LTI) systems, which our climate is most assured not.

For the same reason, the only scientifically valid conclusion one can draw when observations exceed the confidence intervals of the model, as recent MGT observations have, is that the model is invalid. This is true whether exiting on the low side or high side. It is inaccurate to say AGW is better (or worse) than we thought and therefore or century scale projections must be adjusted downward (or upward). The only thing one can say is that at this point in GCMs development, they have nothing predictive to offer to the policy debate nor can they be used to identify the source of observed warming (or cooling) trends.

Again, I’ll make the point that if sulfates are not the primary reason for the episodic nature of the global temperature history of the past 100 years or so, then the climate models have some serious issues to deal with.

-Chip

Over the past 3 decades, there have been many observations that suggest natural variability have increased temperatures rather than decreaesed : el Nino dominant phase of the PDO, el Chichon+Pinatubo in the 80 & 90 and the exceptional 98 el Nino which conjure to skew the temperature trend up, the high solar activity of the past 3 solar cycles (they are among the 6 cycles with most sunspots for more than 3 centuries).

The fact that Swanson et al -and Dr Romm- chose only the high sensitivity hypothesis in their conclusion is evidence that their speculation is biased by at best PC conformity pressure, at worse unscientific and preconceived views.

It is definitely complicated. I agree with Dr. Swanson that when the climate shifts, then the temperature will increase at a faster rate (then present), but, I don’t necessarily agree that it will be at a rate much greater than expected. For instance, the warming during the 1980s and 1990s (presumably part of which was being stored up by the cooling state of the 1940-1970s) wasn’t greater than expected (from climate models). Observations seem to indicate that during Swanon&Tsonis’s “cool” periods, global temperature rise doesn’t occur very fast (despite increases in radiative forcing from growing greenhouse gas concentrations), and that during Swanson&Tsonis “warming” periods, the warming occurs along the lines of model expectations. Take the two periods together, and you get less total warming than projected.

-Chip

““When the climate kicks back out of this state, we’ll have explosive warming,” Swanson said. “Thirty years of greenhouse gas radiative forcing will still be there and then bang, the warming will return and be very aggressive.”” From the article in Discovery

““We realized a lot of changes in the past century from warmer to cooler and then back to warmer were all natural,” Tsonis said. “I don’t think we can say much about what the humans are doing,” he added.” From a local paper in Wisconsin.