The Sun is apparently more active now that it has been for 1000 years. Could this have anything to do with global warming? Well . . . they're working on it.

Comments

[Patrick R. Sullivan]

Sally Baliunas is the go to girl on this, and has been for many years. Here's an interview with her, conducted by the Postrel's:

http://reason.com/9810/fe.baliunas.shtml

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Reason: How do you know magnetic records of the sun from the 17th century?

Baliunas: The records of sunspots go back to 1609, to Galileo's day, and that's almost long enough to see this episode. But we have some unbiased records: The sun has a wind that carries the magnetic field toward the earth and acts as a shield. There's a rain of cosmic rays coming from deep space. When the sun's magnetic field is strong, these cosmic rays tend to be deflected. When the magnetic field is weak, these cosmic rays penetrate the upper atmosphere of the earth. When the cosmic rays come in, they make radiocarbon in the upper atmosphere, and that carbon-14 ends up in carbon dioxide molecules. It's breathed in by a tree and put in its tree ring, so the amount of carbon-14 over time in tree rings tells you what the sun has been doing in the past. Those records trace the sun back about 10,000 years. So we know the ups and downs of the sun's magnetism for the last 10,000 years or so.

After looking at this, I began to ask, How well do the climate simulations handle this relatively new knowledge about the sun? And the answer is, not very well. We don't know the mechanism for change in the sun very well. We don't know the response of the earth to such changes. So I thought, How do you make predictions 100 years in the future if you don't even know what all the sources of change are?

Reason: If the magnetic activity on the sun is changing, what mechanisms are there that might affect the earth's climate?

Baliunas: It depends what time scale one is talking about. The sun brightens and fades over the sunspot cycle, the 11-year cycle. But also the intensity of the 11-year cycles has been building over the centuries.

Reason: What do you mean by "intensity"?

Baliunas: Looking back several hundred years, the sun's magnetism is at an all-time high. The last four peaks have been quite high.

Reason: Do these fluctuations produce a big effect?

Baliunas: It's relatively small from cycle to cycle, but we estimate that from the 17th century to now it could have been four or five tenths of a percent of the sun's energy output. Run that through a climate model, and that's enough to explain the temperature change.

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[David Bradley]

I heard Baliunas talking on this subject earlier in 2003 and did a write-up for Reactive Reports chemistry news webzine at the time (issue 32, July 2003). Her talk was interesting, but I believe she gets lots of opposition from the "pro" lobby. Any thoughts?

db