The Intergovernmental Panel on Climate Change (IPCC) introduced the idea of tipping points two decades ago.

At that time, these ‘large-scale discontinuities’ in the climate system were considered likely only if global warming exceeded 5 °C above pre-industrial levels. 

Information summarized in the two most recent IPCC Special Reports (published in 2018 and in September this year)2,3 suggests that tipping points could be exceeded even between 1 and 2 °C of warming (see ‘Too close for comfort’). 

https://www.nature.com/articles/d41586-019-03595-0