The whole thrust of that article hinges on Willson’s ACRIM dataset. Here’s a quote from Lockwood & Frohich 2008 (see yesterday’s post).

 Fröhlich (2006) has shown that the PMOD composite is consistent with the independent, but relatively noisy, ERBE data, whereas the ACRIM and IRMB are not. Here, we point out that the TSI modelling of Wenzler et al. (2006) from ground-based magnetograms is also consistent with the PMOD composite and inconsistent with ACRIM and IRMB.

This is a killer point, you cannot ignore it if you want to be considered scientific. A text search of the D’Aleo document  for “Wenzler” reveals no instances. ERBE is discussed, claiming it is in support of an upward trend. But as Frohlich 2006 found ERBE actually supports PMOD, and if there’s any confusion here it can be cut through by the agreement between Wenzler and PMOD.

That’s before we get to the issue of what the small increase of ACRIM implies if it does indeed support a driving of global temperature. Because if we are to accept that the small increase in ACRIM since 1975 was the driver of the observed warming over that period, there was an even more massive increase of TSI from 1900 to 1950 e.g.
http://lasp.colorado.edu/sorce/data/tsi_data.htm
- proportionately this should have resulted in a temperature increase massively greater than that since 1975. This did not happen.

Solar output correlates well with global and northern hemisphere temperature up to the middle of the last century. Yet neutron flux shows no trend. To claim cosmic rays and committed warming explains the post 1975 warming is clutching at straws. There is no formal modelling supporting this claim. And all this when over 100 years of physics predicts that higher CO2 will cause warming, physics supported by formal modelling, with warming occurring at the same time as the CO2 increase is occurring. To be clear: NO model shows warming when only natural factors are included, ALL the models show the post 1975 warming at the same time when forced with anthropogenic and natural forcings showing that it is a forced response, whereas the 1940s warming does not occur to the same degree in all models suggesting that warming had a large component of internal variability (e.g. Johanessen et al 2004, “Arctic climate change: observed and modelled temperature and sea-ice variability”).

There is no need to resort to some solar factor X to explain the recet hiatus in the warming trend. Kaufman et al 2011 “Reconciling anthropogenic climate change with observed temperature 1998-2008″ and Foster & Rahmstorf, 2011, “Global temperature evolution 1979–2010″ both find that ENSO, sulphate aerosols and solar variability account for the abatement of the warming trend in the first decade of the 21st century. That’s two different papers by two different groups of scientists using different methods that are in broad agreement. To quote from Kaufman:

“The finding that the recent hiatus in warming is driven largely by natural factors does not contradict the hypothesis: “most of the observed increase in global average temperature since the mid 20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.”"
So let’s apply Occam’s Razor.

The good agreement between temperatures and solar pre 1975 is accepted in both cases. 1975 is chosen as the start of the ~0.17degC warming trend in the GISS LOTI dataset, that warming trend started in the mid 70s hence 1975 as a reasonable extimate of inflection.

Option 1, It’s all solar. This requires a new solar factor to manifest itself after 1975 to explain the observed warming and to be congruent with the lack of increase of surface insolation observed by Wild et al. To be clear this is a solar factor not apparent prior to that period because the preceding correlation between solar and temperature does not require recourse to an unknown factor, merely using long standing estimates of solar flux based on sunspots. Furthermore the introduction of a new ‘factor X’ implies an additional burden – to explain why the increase of CO2 is not causing warming when longstanding physics tell us it will.

Option 2. The pre-1975 warming had a large solar component, explaining much of the preceding warming and cooling back to the LIA and MWP. However after 1975 human emissions of CO2 took over from solar factors driving the observed warming.

From Wikipedia – “{Occam’s Razor} is a principle urging one to select among competing hypotheses that which makes the fewest assumptions and thereby offers the simplest explanation of the effect”.

Option 2 offers the simplest explanation, therefore as the most parsimonious solution it is to be preferred.

I believe Motl to be a sharp guy. But why doesn’t he publish?
Get his rebuttal into the science circles. If he doesn’t play the science game how is he supposed to have an impact?

http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-7.html#2-7-1

2.7.1 Solar Variability

The remaining text is at the link.

The most likely mechanism is considered to be some combination of direct forcing by changes in total solar irradiance, and indirect effects of ultraviolet (UV) radiation on the stratosphere. Least certain, and under ongoing debate as discussed in the TAR, are indirect effects induced by galactic cosmic rays (e.g., Marsh and Svensmark, 2000a,b; Kristjánsson et al., 2002; Sun and Bradley, 2002).

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Those that can’t stand the idea of AGW jump to the cosmic puddle every chance they get. All these papers above for cosmic rays don’t really understand the mechanism yet. That’s still being studied.

It is also disturbing that you join in with what amounts to a sordid bullying campaign against Dr Mann, when I count 16 other authors in the studies shown on that page. All of those authors contributed to studies that show that the current warming is highest temperature in at least 1000 years.
Furthermore changes in solar radiation seems likely to be the main driver of changes in temperature during the LIA/MWP. However this clearly does not aply now. For example Wild et al, 2007, “Impact of global dimming and brightening on global warming.” investigated results from the GEBA and BSRN surface insolation monitoring networks. They find that the global warming is not being driven by changes in sunlight.
I quote:”Despite the fact that surface insolation at the turn of the millennium is rather lower than in the 1960s, land surface temperatures have increased by 0.8
C over this period (Figure 1). This suggests that the net effect of surface solar forcing over the past decades cannot be the principal driver behind the overall temperature increase, since over the past 40 years, cooling from solar dimming still outweighs warming from solar brightening. Rather, the overall temperature increase since the 1960s can be attributed to greenhouse forcing as also evident in the BSRN data outlined above. Thus, speculations that solar brightening rather than the greenhouse effect could have been the main cause of the overall global warming over the past decades appear unfounded.”

This is also supported in terms of direct satellite observations of solar output. Lockwood & Frohlich produced a 2008 paper: Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature. http://rspa.royalsocietypublishing.org/content/464/2094/1367.fullThis finds that there is no conceivable way the Sun could be resonsible for the post 1975 global warming, and that other datasets (e.g. ACRIM) have substantial problems in explaining the warming.
I quote:”Hence, like many authors before us, we conclude there is no credible way that the recent rise in air surface temperature can be attributed to solar effects. As in paper 1, Lockwood et al. (1999) and Solanki & Krivova (2003), we have not drawn on complex general circulation climate models to draw this conclusion.”

Lockwood has publicly stated:”I even believe that you can detect in the climate record a solar influence up until about 1940… …The trouble is that about 1960 solar variability started to become dominated by fossil fuel burning and greenhouse gases.”

Carl Wunsch, notable for his scepticism and challening of established
scientific ideas (e.g. “Abrupt climate change: An alternative view” Quaternary Research 2006) has also publicly stated: “In terms of the last 30 years I’d have to agree that there’s nothing in these records that suggests solar variability could be giving rise to warming global temperatures.”

So we know that in a period when CO2 is rising due to human activities the sun, whilst responsible for past warmings and cooling is not responsible. We also know that CO2 causes an increase in the greenhouse effect causing warming.

I have to wonder what is driving your arguments – because it clearly is not the evidence!

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Back to your conclusion. As I read through summations on the literature on MWP, there were definite warm areas and also areas that were cool.

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http://www.skepticalscience.com/new-remperature-reconstruction-vindicates.html

Figure 2.  Comparison of northern hemisphere and global temperature reconstructions.  Northern hemisphere instrumental temperature records shown for comparison (CRUTEM land only, and HADCRUT land/ocean).

Someone has done the work for us to show several reconstructions during this period. MWP and LIA is recognized in their work. Along with present day temperatures. They show temperatures about equivalent to mid 20th century.

http://www.skepticalscience.com/medieval-warm-period-i ntermediate.htm

figures 2 and 3 as I’ve discussed in a previous post when compared to the 1961 to 1990 average shows todays globe to be substantially warmer.

 http://www.skepticalscience.com/medieval-warm-period-basic.htm

the Medieval Warm Period has known causes which explain both the scale of the warmth and the pattern. It has now become clear to scientists that the Medieval Warm Period occurred during a time which had higher than average solar radiation and less volcanic activity (both resulting in warming). New evidence is also suggesting that changes in ocean circulation patterns played a very important role in bringing warmer seawater into the North Atlantic.

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The knowledge of today shows we have a good idea of why the MWP was warm locally and not globally.

Today we are warming globally and understand why. Mostly human emissions of GHG’s which has no precedent in human or geological history.