2011-09-16 08:18:05New paper on internal climate variability
Julian Brimelow

Just saw this new paper by DelSole et al. in J. Climate



The problem of separating variations due to natural and anthropogenic forcing from those due to unforced internal dynamics during the twentieth century is addressed using state-of-the-art climate simulations and observations. An unforced internal component that varies on multidecadal time scales is identified by a new statistical method that maximizes integral time scale. This component, called the internal multidecadal pattern (IMP), is stochastic and hence does not contribute to trends on long time scales; however, it can contribute significantly to short-term trends. Observational estimates indicate that the trend in the spatially averaged “well observed” sea surface temperature (SST) due to the forced component has an approximately constant value of 0.1 K decade−1, while the IMP can contribute about ±0.08 K decade−1 for a 30-yr trend. The warming and cooling of the IMP matches that of the Atlantic multidecadal oscillation and is of sufficient amplitude to explain the acceleration in warming during 1977–2008 as compared to 1946–77, despite the forced component increasing at the same rate during these two periods. The amplitude and time scale of the IMP are such that its contribution to the trend dominates that of the forced component on time scales shorter than 16 yr, implying that the lack of warming trend during the past 10 yr is not statistically significant. Furthermore, since the IMP varies naturally on multidecadal time scales, it is potentially predictable on decadal time scales, providing a scientific rationale for decadal predictions. While the IMP can contribute significantly to trends for periods of 30 yr or shorter, it cannot account for the 0.8°C warming that has been observed in the twentieth-century spatially averaged SST.

And the last sentence is the kicker.  What concerns me is if the warming phase of the IMP kicks in when CO2 levels much higher than today, b/c on short time sclaes, the contribution in wamring can be quite significant.

2011-09-16 08:38:28
Dana Nuccitelli

Would be good to do a post on this and add it to the 'internal variability' rebuttal.

2011-09-16 08:41:15comment
Robert Way


He had this on his website long ago.. guess it finally got published. Like i've said many times in the past on here... the AMO is very important... It goes positive you get acceleration, negative the converse. A paper I submitted recently (fingers crossed) discusses this in a regional context.

2011-09-17 03:33:31


Talking of internal variability, what happened to this study which John warned us about earlier this year

NASA Study Goes to Earth's Core for Climate Insights 

Is anyone aware of any developments of underlying theories explaining how it could affect temperatures?  Should it the added to the rebuttal?