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Study of the sun-climate link was energized in 1991 by Friis-Christensen and Lassen, who showed a strong correlation between solar-cycle length and global temperature:

This evidence that much of 20th century warming might be explained by solar activity was a thorn in the side of the newly powerful CO2 alarmists, who blamed recent warming on human burning of fossil fuels. That may be why Lassen and Thejll were quick to offer an update as soon as the 1997-98 El Nino made it look as if temperatures were suddenly skyrocketing:

The rapid temperature rise recently seems to call for a quantitative revisit of the solar activity-air temperature association …

We conclude that since around 1990 the type of Solar forcing that is described by the solar cycle length model no longer dominates the long-term variation of the Northern hemisphere land air temperature.



In other words, there was now too much warming to account for by solar cycle length, so some other factor, such as CO2, had to be driving the most recent warming. Of course everyone knew that the 1998 warming had actually been caused by ocean oscillations. Even lay people knew it. (El Nino storm tracks were all the news for six months here in California.)

When Lassen was writing his update in mid ’99, temperatures had already dropped back to 1990 levels. His 8 year update was outdated before it was published. 12 years later the 2010 El Nino year shows the same average temperature as the ’98 El Nino year, and if post-El Nino temperatures continue to fall off the way they did in 99, we’ll be back to 1990 temperatures by mid-2011. Isn’t it about time Friis-Cristensen, Lassen and Thejll issued another update? Do they still think there has been too much recent warming to be accounted for by solar activity?

The most important update may be the discovery that, where Lassen and his colleagues found a correlation between the length of a solar-cycle and temperatures over that cycle, others have been finding a much stronger correlation to temperatures over the next cycle (reported at WUWT this summer by David Archibald).

Click source to read FULL report from Alec Rawls (guest post at WUWT)