Unfortunately, there are a number of potential tipping points that could, if crossed, eventually trigger what’s known as ‘runaway’ climate change in which natural processes take over and temperatures rise regardless of what humans do.
Just as it is important to take this seriously, it is also important we do not allow ourselves to give in to despair.
The IPCC report spoke of events like “ice sheet collapse and abrupt ocean circulation changes” as being of low-likelihood, while warning they were “associated with potentially very large impacts, such as through more intense and more frequent heatwaves and heavy precipitation, and high risks for human and ecological systems”.
This is one reason why we should try to keep global warming from going above 1.5 degrees Celsius.
Another potential tipping point is the effect of warming temperatures on boreal forests in Russia, Canada and Scandinavia, which are estimated to hold more than a third of all terrrestrial carbon.
Temperatures there have been rising more rapidly than the global average and the fear is that the dominant tree species may start to suffer higher levels of disease, lower rates of reproduction and higher death rates, resulting in more wildfires that release large amounts of stored carbon into the atmosphere.
But, of course, wildfires are not just a problem in the far north. In California, firefighters have been wrapping fire-resistant blankets around some of the trees in the Sequoia National Park as flames from two major fires approach.
Among them is the biggest known single-stem tree on the planet, nicknamed ‘General Sherman’, which, at 275 feet, would tower over Edinburgh’s Scott Monument.
But the fire blanket is, almost literally, a sticking plaster on a much bigger problem. Perhaps it would be better to let General Sherman burn because there is another kind of tipping point, one that exists in our minds: the point at which we realise just how serious our situation is.
The loss of a wonderful and awe-inspiring tree that has stood for about 2,500 years might just help us make that mental leap so that, “abruptly and irreversibly”, we commit to taking the necessary action.