The scale that humans have altered Earth’s life support system

Here are some surprising facts about humans’ effect on planet Earth. We have made enough concrete to create an exact replica of Earth 2mm thick. We have produced enough plastic to wrap Earth in clingfilm. We are creating “technofossils”, a new term for congealed human-made materials – plastics and concretes – that will be around for tens of millions of years.

But it is the scale that humans have altered Earth’s life support system that is the most concerning.

In 2000, Nobel laureate Paul Crutzen and Eugene Stoermer proposed that human impact on the atmosphere, the oceans, the land and ice sheets had reached such a scale that it had pushed Earth into a new epoch. They called it the Anthropocene and argued the current Holocene epoch was over.

The Holocene began 11,700 years ago as we emerged from a deep ice age. Over the past 10,000 years, the defining feature of the Holocene has been a remarkably stable Earth system. This stability has allowed us to develop agriculture and hence villages, towns and eventually cities – human civilisation.

We use pretty powerful rhetoric to describe the Anthropocene and current human impact. As The Economist stated in 2011, humanity has “become a force of nature reshaping the planet on a geological scale”. We are like an asteroid strike. We have the impact of an ice age.

But what does this really mean? Does it mean, for example, that we are having as big an impact as these natural forces are having right now, or is it, somehow, more profound?

In our recent study, we wanted to find the simplest way to mathematically describe the Anthropocene and articulate the difference between how the planet once functioned and how it now functions.

Life on Earth, the chemical and physical composition of the atmosphere and oceans, and the size of the ice sheets have changed over time because of slight alterations to Earth’s orbit around the sun, changes to the sun’s energy output or major asteroid impacts like the one that killed the dinosaurs.


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