Learning to read a glacier

We left the hut at five, roped in teams of three, boots biting the crust. The glacier does not look like it moves. It looks like a very large, very cold motorway stopped at a bend. But the stakes the team had drilled in autumn were two metres lower down the slope than they had been a year ago.

Measuring is slow, repetitive work. Someone calls out a number, someone writes it down, and the third person checks it against last year's. The most important instrument of the trip is a notebook with a pencil tied to it.

What the ice remembers

Cores drilled from older glaciers hold layers: ash from volcanoes, soot from industry, pollen from forests that no longer exist. Reading them is like reading a diary written by someone who never edited.