Some trees alive today were already old when the oldest buildings in most cities were new. Bristlecone pines in the mountains of the western United States have been dated at more than four thousand years, and many oaks and yews in Europe are several centuries old.

We can count a tree’s age without cutting it down. A thin core drilled from the trunk shows its growth rings: one pale band of fast spring growth and one dark band of slower summer growth for each year. Wide rings mean good years; narrow ones, drought or cold.

Because neighbouring trees share the same weather, their patterns of wide and narrow rings match. Lining up those patterns, from living trees through old timbers to ancient wood, scientists have built records of climate reaching back thousands of years.

Every old tree is an archive. It is worth stopping beside one, now and then, to think about everything it has stood through.