Article: Breaching a ‘carbon threshold’ could lead to mass extinction
What do tipping canoes, phase transitions like water freezing to ice, breaking sticks, chopping down dead trees, the carbon cycle in the ocean, and human relationships all have in common? Answer: they are highly nonlinear, dynamic systems that exist in stable states until pushed by some factor above so-called critical thresholds.
One characteristic of the five large mass extinctions in Earth’s geological history is disruption of the ocean carbon cycle, causing large, rapid ocean acidification. Then abrupt disruption sweeps the systems towards a new, distant, eventually stable state that will not be favorable for the survival of most life on Earth.
Acidification is proceeding extremely fast today, in what is a human-caused sixth mass extinction. Some of the rapidly rising carbon dioxide in our atmosphere reacts with water forming carbonic acid, dissociating to bicarbonate ions, then carbonate ions, making the oceans much more acidic. Like a canoe reaching the tipping point, the ocean carbon cycle can cross a threshold and tip as we drive emissions ever higher.