Oxygenation of Earth’s atmosphere may not have required a trigger event after all

In Earth history, there have been 3 abrupt jumps in atmospheric oxygen. A evolutionary or tectonic trigger is usually invoked, but a new study just published in Science suggests all you need is gradual oxidation of earth’s surface plus feedbacks within & between the P(hosporous), C(arbon) and O(xygen) cycles.

A timely reminder that the Earth system is complex and full of non-linear responses to anything which prods it. Any change doesn’t just depend on the size of the prod, but also the state of the planet when it is being prodded. Kicking a pebble in a valley and kicking one on a steep scree slope can lead to very different results! Or more accurately in this case, you can slowly add dozens of pebbles to a pile and nothing happens – until you add the last one that collapses the whole thing.

If you ever hear about climate ‘tipping points’, this is what is meant: we may get to where the accumulated changes that our civilisation is imposing on the Earth system push it into a state where even a small further push is like the final pebble on the pile.

If you ever hear about climate ‘tipping points’, this is what is meant: we may get to where the accumulated prods that our civilisation is making on the Earth system push it into a state where even a small further prod is like the final pebble on the pile. Most importantly, once the threshold is crossed, and non-linear changes have started cascading through the system, we are all along for the ride.