Part 3: Tipping points
What are tipping points?
A tipping point in a complex system is a point where a small change makes a big difference and alters the state or fate of a system. For climate tipping points, this means that there are thresholds at which a tiny change can shift a system into a completely new state. This process is irreversible in human timescales, and once tipped, it is virtually impossible to stop.
The following picture shows an example of a tipping point. When the glass is in the center of the table, it is in a stable state. We can push the glass across the table and not much happens at the beginning. But as soon as the glass reaches the edge of the table, i.e. the tipping point, it will tip over if we push it a little further. After we push it over the edge, the state of the glass will quickly change without any other external influence until it hits the ground. At the floor, the glass is in a stable state again, but it might be shattered, so we might not like the new stable state. After the glass hits the floor, we may not be able to return it to its original state on the table, and even if we could (in the case it’s not shattered after the fall), we would need much more energy than we used to push it over the edge.
Climate tipping points work in a similar way. Once we cross them, our climate will change significantly. We should also be careful not to get too close to these tipping points, because if they are very close, natural fluctuations could push us over the edge.
Another reason I used this cat gif is because I think the cat perfectly illustrates our current behavior. In the original video, the owner tells the cat to stop pushing the glass. The cat looks at the owner and at first looks like it is listening, but then it pushes the glass over the edge anyway.
Similarly, scientists have been warning us about climate change and climate tipping points for decades. And although 195 countries have signed the Paris Agreement, almost none of them (if any) are doing what is necessary to stop climate change, and so we are pushing the climate toward many tipping points.
Climate tipping points
Scientists have already identified many climate tipping points. Since this article would get too long if I explained them all here, I’ve written a series of short sub-articles about some of them. These articles answer 3 questions about each tipping point:
- Why is this system a tipping point?
- Where is this tipping point?
- What would happen if we crossed the tipping point?
List of climate tipping points articles:
- 3.1: Coral Reefs
- 3.2: Greenland ice sheet
- 3.3 West Antarctic Ice Sheet (WAIS)
- 3.4 Atlantic Meridional Overturning Circulation (AMOC)
- 3.5 Amazon rainforest
- 3.6 Boreal forest
- 3.7 Permafrost
The tipping points described above do not constitute an exhaustive list of potential tipping points. There are a number of other parts of the Earth system that have the potential to display tipping point behaviour including: Alpine glaciers, West African monsoon shift, Indian monsoon shift, El Niño Southern Oscillation, Arctic summer sea-ice, Arctic winter sea-ice and the East Antarctic Ice Sheet.
Crossing each of these tipping points would have different consequences, but what they all have in common is that it would certainly be bad for us.
Crossing individual climate tipping points would be bad enough, but a real disaster would be if so many tipping points were crossed that a self-reinforcing feedback loop was created, with one climate tipping point triggering another, and so on. In such a scenario, the Earth would continue to heat up even if human emissions were reduced or eliminated altogether. This paper showed that such a planetary tipping point could exist. The following figure shows the climate tipping points they considered and how they might interact with each other.
Based on their analysis of tipping cascades, they suggest that a potential planetary threshold could be reached at a temperature increase of ∼2.0 °C above pre-industrial levels and could rise sharply beyond that. They also emphasize that they have taken a risk-averse approach to their analysis because the consequences of exceeding this threshold would be catastrophic. Scientists warn that if we trigger this cascading effect, it would be “an existential threat to civilization”.
To put this in perspective: If all countries were to meet their current pledged emissions reductions, we would still be on track for 2.7°C warming. And many countries are not even close to achieving their promised emissions reductions. So if we want to make sure that we don’t wipe out our civilization, we should do everything in our power to comply with the Paris Agreement. And to have any chance at all of keeping the Paris Agreement, we need to start acting NOW. We only have control over our own future if we don’t trigger this tipping point cascade.