How extreme weather leaves a lasting mark on trees and shrubs POZNAŃ, Poland — In the Arctic’s harsh borderlands, where trees wage a constant battle for survival, an international research team has ...

Volcanic eruptions and cold summers leave lasting marks in the wood of northern trees, unlocking the secrets of past climate extremes.

So, if you see a tree that has blue paint marks, be respectful and avoid crossing the property owner's border. And what if you spot a tree painted entirely blue, even the tips of its branches?