Well, they only had accurate daily sunspot measurements dating back to 1854.
A much better article on the report:
http://news.nationalgeographic.com/news/2006/09/060913-sunspots.html
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Sun Not Off the Hook for Warming
The authors and other experts are quick to point out that more complicated solar mechanisms could possibly be driving climate change in ways we don't yet understand.
Climate change carries such high stakes that even more unlikely possibilities may capture scientific attention.
"There are numerous studies that find a correlation [between solar variation and Earth climate]," said Sami Solanki of the Max Planck Institute for Solar System Research in Lindau, Germany.
"These authors have looked at the simplest mechanism, and they find that this mechanism does not produce the same level of change that has been observed," he continued.
"This could be suggesting that there are other mechanisms acting for the way that the sun influences climate."
Solar ultraviolet (UV) rays are one possibility, though that theory creates its own challenges.
"UV is only a small fraction of total solar output, so you'd need a strong amplification mechanism in the Earth's atmosphere," study co-author Spruit said.
Magnetized plasma flares known as solar wind could also impact Earth's climate. Solar wind influences galactic rays and may in turn affect atmospheric phenomena on Earth, such as cloud cover.
Such complex interactions are poorly understood but could be crucial to unlocking Earth's climatic puzzle.
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Goldstein has studied the impact solar flares have on earth communications which are heavily impacted by the disappearance of the outer shield....it's not a big jump in reasoning to see that without the shielding,....particles from outer space reach deeper into the atmosphere....
So, even though there is clear correlation with sunspots, cosmic rays and climate, we have dozens of politicians claiming that "The debate is over. The science is in. Mankind is causing global warming".
Sickening.