Anthropocene

When people talk about the “Anthropocene,” they typically picture the vast impact human societies are having on the planet, from rapid declines in biodiversity to increases in Earth’s temperature by burning fossil fuels. Such massive planetary changes did not begin all at once at any single place or time. That’s why it was controversial when, after over a decade of study and debate, an international committee of scientists – the Anthropocene Working Group – proposed to mark the Anthropocene as an epoch in the geologic time scale starting precisely in 1952. The marker was radioactive fallout from hydrogen bomb tests. On March 4, 2024, the commission responsible for recognizing time units within our most recent period of geologic time – the Subcommission on Quarternary Stratigraphy – rejected that proposal, with 12 of 18 members voting no. These are the scientists most expert at reconstructing Earth’s history from the evidence...

As scorching heat grips large swaths of the Earth, a lot of people are trying to put the extreme temperatures into context and asking: When was it ever this hot before? Globally, 2023 has seen some of the hottest days in modern measurements, but what about farther back, before weather stations and satellites? Some news outlets have reported that daily temperatures hit a 100,000-year high. As a paleoclimate scientist who studies temperatures of the past, I see where this claim comes from, but I cringe at the inexact headlines. While this claim may well be correct, there are no detailed temperature records extending back 100,000 years, so we don’t know for sure. Here’s what we can confidently say about when Earth was last this hot. This is a new climate state Scientists concluded a few years ago that Earth had entered a new climate state not seen in more than 100,000 years. As fellow climate scientist Nick McKay and I recently discussed in a scientific journal art...