What are climate tipping points and how were they discovered? Could positive social tipping points be key to the challenges we now face? Tim Lenton, who pioneered the science of climate tipping points looks back at their history and at what lies ahead for planet earth.

A tipping point is where a small change makes a big difference to a system. They are an example of ‘non-linearity’ – output is not proportional to input. Non-linearity can happen when strongly self-reinforcing feedbacks are present. The initial small change follows a closed-loop of causality that feeds back to amplify it. Then the now larger change goes around the loop and gets further amplified, and so on.

For example, as the Arctic sea-ice melts it exposes a much darker ocean surface that absorbs more sunlight, warming the region and melting more sea-ice, which warms things further, and so on. Or when Greta Thunberg started her school strike in front of the Swedish parliament, she made it incrementally easier for the next person to join her, who made it slightly easier for the next person, and so on.