Has the climate recently shifted? (PDF)
Here are the paper's conclusions:
"Finally, it is vital to note that there is no comfort to be gained by having a climate with a significant degree of internal variability, even if it results in a near-term cessation of global warming. It is straightforward to argue that a climate with significant internal variability is a climate that is very sensitive to applied anthropogenic radiative anomalies (c.f. Roe [2009]). If the role of internal variability in the climate system is as large as this analysis would seem to suggest, warming over the 21st century may well be larger than that predicted by the current generation of models, given the propensity of those models to underestimate climate internal variability [Kravtsov and Spannagle 2008].
"Finally, it is vital to note that there is no comfort to be gained by having a climate with a significant degree of internal variability, even if it results in a near-term cessation of global warming. It is straightforward to argue that a climate with significant internal variability is a climate that is very sensitive to applied anthropogenic radiative anomalies (c.f. Roe [2009]).
When they can also account for phenomena external to our atmosphere, I might get concerned about a minor increase in a trace gas.
If the role of internal variability in the climate system is as large as this analysis would seem to suggest, warming over the 21st century may well be larger than that predicted by the current generation of models, given the propensity of those models to underestimate climate internal variability [Kravtsov and Spannagle 2008].
I'll believe in a model when they have one that can reproduce the historical data.
This is an example of the well-known "save-the-grant-money" quote. Catalog it with "more research is needed." Obviously, a huge system with high variability will be less susceptible to miniscule imfluences, not more. If you doubt it, go out in a raging river sometime and hold out your arms-- see what impact you have.