I have also read only the abstract, which makes any comments somewhat tentative. However:
The paper does not appear to have taken into account the rise in cloud cover which others (Spencer, Lindzen) have proposed as providing negative feedback. It thus does not appear to address the Spencer work, or counter it, of course.

http://www.agu.org/pubs/crossref/2008/2008GL035333.shtml

It appears they are coming to exactly opposite conclusions based on the same satellite data.

Here is the link to Roy Spencer’s CA visit and thread on the cloud effects not as a feedback:

http://www.climateaudit.org/?p=2543#comments

I think Spencer’s model can obtain temperature changes of the magnitude of those in the modern day warm period without invoking PDO/ENSO. Applying his model to PDO/ENSO seems (on my quick read) more like confirming or at least giving evidence for them as internal variations.

For instance, the major features of global mean temperature variations since 1900 (Fig. 2a) have usually been explained as a combination of anthropogenic greenhouse gas and aerosol emissions, possibly combined with a small amount of increased solar forcing (IPCC, 2007). While this is indeed one possible explanation, it is also possible that some part of the temperature change represents internal variability in the climate system in the form of radiative forcing which is not the result of feedback. After all, it is well known that ENSO has warm and cool phases which occur irregularly every few years, and that the warm phase (El Nino) has been more frequent during the warming experienced since the 1970′s (see Fig. 2b). Similarly, the lower-frequency Pacific Decadal Oscillation (PDO, Mantua et al., 1997) was more often in its positive phase during the period of global mean warmth around 1940, as well as during the warming since the 1970s (Fig. 2c)…

..It is not unreasonable to hypothesize that the small changes in atmospheric and oceanic circulation associated with these modes of climate variability have caused corresponding non-feedback changes in clouds, which then impact the radiative budget of the Earth…

..We will hypothesize that the PDO and ENSO indices have associated with them some amount of internal radiative forcing due to cloud changes. Again using the basic form of Eq. 1, we now assume that the only heating term is a linear function of the SOI and PDO indices,

Cp dT/dt = α (βPDOPDO + βSOISOI ) – λT (2)

where βPDO + βSOI = 1. (3)

I think this closing statement is an important summarization of Spencer’s thesis vis a vis the conventional theory.

While it might be argued that the mechanism proposed here is speculative, it is also speculative to assume that the radiative flows of energy in and out of the Earth system are stable to much less than 1% of their mean (of about 235 W m-2) on multi-decadal time scales in the presence of known modes of internally generated climate variability.

For the benefit of other dodoes like me:

http://en.wikipedia.org/wiki/Roy_Spencer
“Roy Spencer is a principal research scientist for University of Alabama in Huntsville. In the past, he served as Senior Scientist for Climate Studies at NASA’s Marshall Space Flight Center in Huntsville, Alabama. Dr. Spencer is the recipient of NASA’s Medal for Exceptional Scientific Achievement.”

http://www.weatherquestions.com/Roy-Spencer-on-global-warming.htm
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To eliminate the effect to a degree commensurate with our ability to measure it you would have to average over 3 or 5 relaxation times. If there is also a known cyclic period to the forcing (sunspot cycles) you would want to adjust your averaging accordingly.

On top of that given sunspot period variability you might want to change the averaging period according to known sunspot cycles. Minimum to minimum.

So you might average over 30 years in some segments of the data and 35 years in other segments. What you do about a Maunder minimum is?????

In one relaxation period about 35% of the effect remains. In 3 relaxation periods only 5% of the effect remains.

In simpler terms: if the random walk has a “direction” due to a few consecutive moves in the same direction over some short span of time, about 35% of that direction will remain in one relaxation period and only 5% of what at first appeared to be a direction will remain after 3 relaxation time periods.