Tree Rings Reveal 1,000 Years of Solar Activity

Solar activity over the last 1000 years (blue, with error interval in white), sunspot records (red curve) going back less than 400 years. The background shows a typical eleven-?year cycle of the sun. CREDIT ETH Zürich

The Sun has a lot of rhythm and goes through different cycles of activity. The most well-known cycle might be the Schwabe cycle, which has an 11-year cadence. But what about cycles with much longer time scales? How can scientists understand them?

As it turns out, the Sun has left some hidden clues in tree rings.

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