A group of researchers at the University of Edinburgh found that Galactic Cosmic Rays cause trees to grow faster.
The sun has an 11 year cycle of solar spots, when there is a lull in sunspots there is a lull in solar wind. The solar wind protects us from GCRs by creating a magnetic repellent.
When the solar wind is low and Galactic Cosmic Rays arrive on earth in larger numbers, trees grow faster. While we don’t know why it might have something to do with weather changes such as increased cloud cover that forms when the rays are hitting earth.
Galactic Cosmic Rays
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A relationship between galactic cosmic radiation and tree rings ( paper $ )