Don,


http://science.nasa.gov/science-news/science-at-nasa/2013/08jan_sunclimate/


You state:"So, unless the Sun itself gets hotter, it isn't going to cause global warming, and we know that the Sun is in a phase where it is, very slowly, cooling."

You assume that the sun is constant, and not variable.

"There are no direct measurements of the longer-term variation and interpretations of proxy measures of variations differ; recent results suggest about 0.1% variation over the last 2,000 years,[4] although other sources suggest a 0.2% increase in solar irradiance since 1675.[5] The combination of solar variation and volcanic effects has very likely been the cause of some climate change, for example during the Maunder Minimum.

A 2006 study and review of existing literature, published in Nature, determined that there has been no net increase in solar brightness since the mid 1970s, and that changes in solar output within the past 400 years are unlikely to have played a major part in global warming.[6] However, the same report cautions that "Apart from solar brightness, more subtle influences on climate from cosmic rays or the Sun's ultraviolet radiation cannot be excluded, say the authors. They also add that these influences cannot be confirmed because physical models for such effects are still too poorly developed."[7]"




"Dan Lubin of the Scripps Institution of Oceanography pointed out the value of looking at sun-like stars elsewhere in the Milky Way to determine the frequency of similar grand minima. "Early estimates of grand minimum frequency in solar-type stars ranged from 10% to 30%, implying the sun's influence could be overpowering. More recent studies using data from Hipparcos (a European Space Agency astrometry satellite) and properly accounting for the metallicity of the stars, place the estimate in the range of less than 3%."   This is not a large number, but it is significant.
Indeed, the sun could be on the threshold of a mini-Maunder event right now. Ongoing Solar Cycle 24 is the weakest in more than 50 years. Moreover, there is (controversial) evidence of a long-term weakening trend in the magnetic field strength of sunspots. Matt Penn and William Livingston of the National Solar Observatory predict that by the time Solar Cycle 25 arrives, magnetic fields on the sun will be so weak that few if any sunspots will be formed. Independent lines of research involving helioseismology and surface polar fields tend to support their conclusion. (Note: Penn and Livingston were not participants at the NRC workshop.)
"If the sun really is entering an unfamiliar phase of the solar cycle, then we must redouble our efforts to understand the sun-climate link," notes Lika Guhathakurta of NASA's Living with a Star Program, which helped fund the NRC study. "The report offers some good ideas for how to get started."