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The collapse of a , the meltdown of or the dieback of the are all examples of negative climate tipping points. These are the big risks associated with a changing climate, where harmful change becomes self-propelling. Each could cause environmental disasters affecting hundreds of millions of people.

The prospect of such irreversible and massively damaging outcomes is looming ever closer, as we are set to exceed 1.5°C global warming. Every year and every 0.1°C above this threshold increases the risk of crossing negative climate tipping points. To avert them, climate action must accelerate spectacularly. We need to decarbonize the global economy than the current rate to have reasonable odds of limiting warming well below 2°C.

This sounds both frightening and daunting. We are facing existential risks and to avoid them requires extraordinary rates and scales of social and technological change. It is understandable to feel climate despair or doomism—particularly with the current spate of .

But there are credible grounds for conditional optimism. They lie in the evidence of positive tipping points—where changes to zero-emission behavior and technologies become self-propelling. This is now the only plausible way we can accelerate out of trouble, because we have left it way too late for incremental change to rescue us.

Tipping points happen when amplifying feedback within a system gets strong enough to support self-propelling change. Like putting the proverbial microphone too close to the speaker. They can happen in a range of systems, and history shows us they have happened repeatedly in social systems. Think of political revolutions, abrupt shifts in social norms—like the abandonment of smoking in public, or the rapid transition from horse-drawn carriages to cars.

Happily, almost everything that contributes to human-induced greenhouse gas emissions could be positively tipped towards zero emissions. It can take a lot of work to bring a system to a tipping point, but some key sectors have already positively tipped, at least in some countries.

from buying petrol and diesel cars to EVs in the space of a decade. The burning. While gas temporarily replaced some of coal's role in electricity generation, has now replaced coal burning and is starting to displace gas. Neither transition happened by chance. Tipping our societies to zero emissions requires deliberate, intentional action from us all.

In Norway, change was started by social activists in the late 1980s, including members of the pop band A-ha, pushing the government to adopt a package of policies to incentivize EVs. In the UK, tipping was triggered by a rising floor price on carbon in the power sector, a policy that can be traced to the Climate Change Act, which started life as a private member's bill, in turn born out of decades of environmental activism.

The beauty of tipping points

In my new book, , I highlight how just a small change can make a big difference. A minority can ultimately tip the majority. That minority activates amplifying feedback loops that get stronger with the more people who join in the change. This means we can all play a part in triggering positive tipping points.

We all make decisions about what we consume. Just by adopting a lower emission technology or behavior (like eating less meat) we encourage others to join us. This is because people imitate one another, and the more people who adopt something the more people they can influence to adopt it too—a phenomenon known as "social contagion".

With technologies, there are extra amplifiers of "increasing returns": the more of us who adopt a new technology, the better it will get (through learning by doing), the cheaper it will get (due to economies of scale), and the more other technologies will emerge that make it more useful. This is how solar PV panels, wind turbines and batteries that power EVs have got ever cheaper, better and more accessible.

Policy usually also plays a crucial role in stimulating positive tipping points. Mandates to phase in clean technologies and phase out fossil-fueled ones are particularly effective. But despite roughly 80% of people worldwide support more decisive action on the climate crisis, governments can dither or be captured by vested interests. Sometimes they need to see what we support.

This may inspire us to get involved with social activism, which has its own tipping points. Each person joining a protest movement makes it incrementally easier for the next person to join. This can reach a critical mass—as it did for Fridays for Future and Extinction Rebellion in 2019. Or if, like me, you are not so comfortable on the march, there are other forms of social activism, like divesting from fossil fuels, or bringing civil cases against companies causing the climate crisis and governments failing to adequately respond to it.

Together a fraction of us can trigger positive tipping points to avoid otherwise devastating negative climate tipping points.