How do we know it’s the hottest month in “125,000 years”?

Question

Somewhere on the Front Page is a reference to this: https://www.axios.com/2023/07/20/world-heat-wave-records-us-europe-china , but how do we guesstimate time re: “spikes that have not been seen for roughly 125,000 years”?

In: 15

Answer 1

We have a pretty good idea of temperatures in geologic times. Various different sequences correlate with temperature: tree ring sizes, isotopes from ice cores, species distribution of pollens in lake sediments, mineralogy of corals, etc.