What is a Tipping Point?

Forcing a system past a tipping point

In everyday usage, a tipping point is where a small change makes a big difference to a system (Gladwell, 2000) (Figure 1) or “the point at which a series of small changes or incidents becomes significant enough to cause a larger, more important change” (Oxford English Dictionary). Here a system is any group of interacting or interrelated things that act according to a shared set of rules to form a recognisable, unified whole – for example, an ice sheet, or an economy. A tipping point is a type of threshold. The small change that causes a system to pass a tipping point can be described as a trigger. The resulting large change can be described as a qualitative change in what a system looks like or how it functions – for example from a Greenland ice sheet to a largely ice-free ‘green’ Greenland, or from an economy powered by fossil fuels to one powered by renewable energy. The change associated with passing a tipping point also commonly includes qualities of: abruptness (change is rapid relative to the drivers forcing it); self-perpetuation (change will continue even if the forcing is removed, until a new state is reached); and irreversibility (change is difficult or impossible to reverse) (Milkoreit et al., 2018). 

Here we define a tipping point as occurring when change in part of a system becomes self-perpetuating beyond a threshold, leading to substantial, widespread,  frequently abrupt and often irreversible impact (inspired by Armstrong McKay et al., 2022 and Milkoreit et al., 2018). This definition includes the possibilities of non-abrupt and reversible tipping points. 

A tipping system is any system that can pass a tipping point. The term tipping element was originally introduced to describe large parts (subsystems) of the climate system (greater than ~1,000km-length scale) that could pass a tipping point (Lenton et al., 2008). Some other disciplines have started to use ‘tipping element’ more broadly to describe those parts or subsystems of a larger system that can undergo tipping point dynamics (e.g. Otto et al., 2020). When used in other contexts a qualifier such as ‘social’ tipping element (Otto et al., 2020) is important to avoid confusion.

Two other terms are widely used in the academic literature often interchangeably with tipping points, and with each other (Dakos, 2019): Regime shift describes an abrupt and/or persistent shift in the current state of an ecosystem from one stable state to another (Biggs et al., 2009; Maciejewski et al., 2019) and critical transition describes an abrupt shift in a system that occurs at a specific (critical) threshold in external conditions (Scheffer, 2009). Thus both describe the change that may be associated with a tipping point, but not the tipping point itself. In this report, we use tipping event to describe the crossing of a tipping point and tipping dynamics to describe the resulting changes that unfold. (Where regime shift or critical transition are used, we define them on a case-by-case basis.)