What was done
The author ruminates on the findings of Lockwood et al. (Nature 399: 437-439).  See our Journal Review More Evidence for a Solar-Climate Link.

What was learned
The author notes that, in addition to the discovery of Lockwood et al. that the general magnetic field of the sun has more than doubled over the past 100 years, the number of sunspots has also doubled over the same time period, and that one consequence of the latter phenomenon is "a much more vigorous Sun" that is slightly brighter.  Parker also draws our attention to the fact that NASA spacecraft measurements have revealed that the brightness of the sun varies by an amount, "change in B/B = 0.15%, in step with the 11-year magnetic cycle."  We are next alerted to the fact that during times of much reduced activity of this sort (such as the Maunder Minimum of 1645-1715) and much increased activity (such as the twelfth century Mediaeval Maximum), brightness variations on the order of change in B/B = 0.5% typically occur.  Parker then notes that the mean temperature (T) of the northern portion of the earth varied by 1 to 2°C in association with these variations in solar activity, stating finally that "we cannot help noting that change in T/T = change in B/B."

And that's not all that the author wonders about.  Knowing that sea surface temperatures are influenced by the brightness of the sun, and that they have risen since 1900, Parker states that "one wonders to what extent the solar brightening [of the past century] has contributed to the increase in atmospheric temperature and CO2" over that period.  Indeed, it is Parker's "inescapable conclusion" that "we will have to know a lot more about the Sun and the terrestrial atmosphere before we can understand the nature of the contemporary changes in climate."

What it means
With respect to the standard hue and cry that is raised about potential CO2-induced global warming in many governmental and political circles, Parker states the obvious: that "it is essential to check to what extent the facts support these conclusions before embarking on drastic, perilous and perhaps misguided plans for global action," noting further that "the biggest mistake that we could make would be to think that we know the answers when we do not."