Past Tipping Points
Tim Lenton
Abstract
Abstract ‘Past Tipping Points’ shows how the climate and human societies have undergone tipping point changes in the past and therefore they could do so again. It starts with the discovery of over twenty abrupt climate changes during the last ice age, recorded in ice cores from Greenland. Each time a tipping point was crossed, the regional climate jumped by nearly 10°C in a matter of decades. The last abrupt warming around 12,000 years ago tipped the climate out of the last ice age. Then a social tipping point from hunting and gathering to farming began – the ‘Neolithic Revolution’. It recurred independently in different parts of the world, as the climate settled into the relative stability of the ‘Holocene’. At first, populations flip-flopped between foraging and farming before reinforcing feedbacks made the transition to farming irreversible. Around 7,000 years ago, the first complex societies started to emerge, tipped by reinforcing feedbacks of escalating internal complexity, escalating conflict with others, and sometimes the challenges of a deteriorating climate. Civilizations spread, but as they aged, they tended to lose resilience. This made them vulnerable to smaller shocks which occasionally tipped them to collapse back to simpler levels of social organization. Finally, capitalism reached a tipping point into sustained economic growth in the Industrial Revolution and came to dominate the world. With the recent ‘Great Acceleration’, its self-propelling feedbacks are now destabilizing the climate and destroying nature, tying our future to that of the Earth system.