When will climate tipping points, actually tip?

28 Jun 2021 07:52 PM

What are climate tipping points and how will we know when they have been breached? A collection of climate scientists provide insight to these fundamental questions by looking at a series of potential tipping points around the world in the second episode of the Mostly Climate podcast, hosted by the Met Office.

The ice sheets of Antarctica are one of the world’s most noted tipping elements. Picture: Shutterstock.

The Met Office’s Dr Doug McNeall is the host of the podcast. He yesterday said:

“The phrase ‘tipping point’ was popularised by Malcolm Gladwell journalist and author who published his first book “The Tipping Point” in 2000. Here he explained how small changes – spreading ideas, messages, behaviours and products – can make a big difference.”

At first the inspiration for the book came from reduced crime rates in New York City, but later expanded to explain similar phenomena in epidemiology. Doug McNeall added:

“Tipping points have since been applied to other areas of science and they have become a large area of research in climate science, whereby small changes can make a big difference to Earth’s subsystems, such the Amazon rainforest or the Atlantic Meridional Overturning Circulation, which includes the Gulf Stream.”

In 2018 and 2020, the IPCC Special Reports suggested that tipping points could be exceeded even if warming was contained between 1-2ᵒC. Professor Tim Lenton – a world-renowned expert on tipping points from the University of Exeter – is a major contributor to the podcast. He highlights that with the probability of crossing tipping points, evidence is mounting they could be more likely to ‘tip’ than previously thought and more attention needs to be given to these high-impact events.

Professor Tim Lenton breaks up Earth’s system into three categories:

• Ice, including elements such as the West Antarctic Ice Sheet and the Greenland Ice Sheet;
• Ocean and Atmospheric Circulation, which includes the Atlantic Meridional Overturning Circulation or Monsoonal systems;
• Biosphere, which includes the Amazon rainforest, or coral reefs.

Tipping points are often considered in isolation, whereby typically parameters are changed very slowly and at some point you reach a critical threshold where the system can collapse. But this isn’t realistic according to Johannes Lohman, due to a phenomenon called ‘rate-induced tipping’. Here we consider that climate change is unfolding at an accelerated pace. Also, there may be other types of tipping points at play. As a result, a system could tip before reaching a critical threshold.

Johannes yesterday explained:

“Rate induced tipping necessitates that the rate of climate change needs to be limited, as well as the absolute amount, since a critical threshold may not be relevant in practice, if parameters and climate change is not slow to change. Due to the chaotic nature of complex systems, there is no well-defined critical rate of change for any one element, severely limiting the predictability of tipping points.”

Next week, in our series on tipping elements on the Met Office news blog we will focus on The Atlantic Meridional Overturning Circulation.

The Met Office’s second episode of Mostly Climate can be found here.