With respect to solar radiation, take a look at Solar flux and sunspots. This site presents data on solar flux, sunspot numbers and a measure of magnetism called the A Index. Click on year 2000 and scroll down through the plots. Observe the striking correlation between solar flux and sunspot numbers. When sunspot numbers go up, so does solar flux. Then look at some year near the bottom of a sunspot cycle when there are few sunspots, like 1985. The level of solar flux is much lower in 1985 than in 2000.
The strong relation between sunspot numbers and solar flux would seem to explain the correlation between the Little Ice Age and the Maunder Minimum period that had almost no sunspots. Oh, I forgot. The IPCC has thrown out the Little Ice Age as a local phenomenon despite its appearance in temperature proxies all over the globe. Can't have that sun doing things to global temperatures.
Someone from the Wilson Observatory made the comment that doubling the CO2 concentration would have roughly the same effect as a 0.1% change in solar radiation. That is certainly in the range of what has been observed for solar variability.
All I can do is cite what appear to be reputable sources.
With respect to solar radiation, take a look at Solar flux and sunspots. This site presents data on solar flux, sunspot numbers and a measure of magnetism called the A Index. Click on year 2000 and scroll down through the plots. Observe the striking correlation between solar flux and sunspot numbers. When sunspot numbers go up, so does solar flux. Then look at some year near the bottom of a sunspot cycle when there are few sunspots, like 1985. The level of solar flux is much lower in 1985 than in 2000.
But there's no doubt about that! The question is whether or not changes in solar flux can appreciably affect climate. That's the reason for the whole search for a climate forcing mechanism related to solar variability. The Bond paper found a linkage because they also looked at radionuclides that are related to solar activity.
The strong relation between sunspot numbers and solar flux would seem to explain the correlation between the Little Ice Age and the Maunder Minimum period that had almost no sunspots. Oh, I forgot. The IPCC has thrown out the Little Ice Age as a local phenomenon despite its appearance in temperature proxies all over the globe. Can't have that sun doing things to global temperatures.
I've been over this with a lot of people. Until very recently, the evidence for the Medieval Warm Period was not as strong as for the Little Ice Age. The recent tree-ring data record of Esper (just published in Nature or Science) strengthens the "strength" of the MWP. Nobody ever really doubted there was one, because the Vikings couldn't have settled in Greenland without one. The Mann tree-ring reconstruction cited by the IPCC didn't eliminate the Little Ice Age (as some skeptics have claimed): it integrated records in which it was quite strong (England and some locations in Europe) with other records where it wasn't as strong or it was timed differently. In fact, Mann has an encyclopedia article on the Little Ice Age online that shows a number of these data sets (it's a PDF document):
Look at the figure on page 5. How anyone can look at this data and say that Mann and the IPCC tried to get rid of the "Little Ice Age" is incomprehensible.
Someone from the Wilson Observatory made the comment that doubling the CO2 concentration would have roughly the same effect as a 0.1% change in solar radiation. That is certainly in the range of what has been observed for solar variability.
And that's quite likely true for the full range of solar variability, including the Maunder Minimum. But the question that needs to be better addressed is what's happening now.