(The least boring)
Once we stop emitting greenhouse gases and destroying ecosystems, the climate will stabilize within 3-5 years
That sounds incredible, and it is, and it is also backed up by scientific consensus. The reason is that terrestrial carbon sinks – all of the photosynthetic organisms that comprise forests, wetlands, grasslands, etc. - draw more CO2 out of the atmosphere more rapidly than previously thought. For decades, the consensus was that we already had 2 deg C heating ‘baked into’ the climate system, so that even if we stopped burning fossil fuels, surface air temperature would continue to rise for decades to hundreds of years. However, climate modelling over the past 10 years or so has demonstrated that this won’t happen, and this new consensus was included in the 2018 IPCC report – though journalists did not pick up on it, and it didn’t occur to the scientists to make a big deal of it. But it is a big deal. HUGE. This is probably the single best piece of good news to come out of climate research since it began.
So does this mean that we’re all clear? Out of the woods? No need to worry about ‘climate change’? No, not at all. But what it does mean is that with real, serious, collective effort, we could press pause. After the initial termination shock, our climate would stabilize at a ‘new normal’ similar to whatever it is when we stop emitting greenhouse gases and destroying the things that remove them from the atmosphere. There are of course a lot of ‘ifs’ here – and as the cautious IPCC itself says, it would require:
“transformative change in all aspects of society”
And the sooner we do this, the less likely it will be that those amplifying, positive feedbacks in the climate and other Earth systems would begin in earnest. Even if they did, it still does not mean game-over for humanity nor many more-than-human beings, though we still would need to stop killing them and destroying their homes directly. Why? Because positive feedbacks do not go on forever, and are not necessarily the end of the world. It all depends on how much fuel we give them.
Positive feedbacks eventually peter out
Positive feedbacks do amplify initial heating, but they do not last forever because the amplifying effect lessens with each iteration of the feedback. The strength of the forcing is important here too – and can be measured as a one-time push to the system, or a smaller forcing but persistent over a longer period of time. The smaller the initial forcing, the smaller and shorter-lived the positive feedback. That said, the forcing needs to stop (i.e., we need to stop greenhouse gas emissions) in order to allow the feedbacks to peter out and the climate to stabilize. Better still would be to not let them begin at all, and that might be possible if we globally reduce our emissions quickly.
Graphic from skepticalscience.com. f = the strength of the forcing, once stopped.
This is not meant to detract from the serious repercussions of allowing positive heating feedbacks in the climate system to begin and continue – the impacts could be devastating. We really want to avoid starting them. Really.
Misunderstandings
However, many well-meaning and understandably freaked-out people who have read up a little on amplifying climate feedbacks have made their own conclusions based on a limited understanding of the science. A famous example was sparked by one non-peer-reviewed commentary (pdf link in first paragraph) in the respected scientific journal Nature, that claimed the Arctic warming – permafrost thaw – methane release feedback from sea sediments had already begun (in 2014) and would release a ‘methane bomb’ once a permanently ice-free Arctic Ocean was established, in six years. It is certainly an important feedback, but time and consensus have shown this prediction to be false (and here, here, and here). The author in question is still at it, even though his theories have been thoroughly disproven by relevant experts. This is why scientific consensus is so important – it tempers the influence of large and loud personalities (or at least it should).
Unfortunately, a professor of business and management took the Nature commentary to heart, ignored scientific consensus, self-published his own paper claiming that The Tipping Point has been passed, and that near-term societal collapse and human extinction was inevitable (though not the first to do so), sending thousands of readers into therapy and to his own new ‘collapse-aware’ cult of personality. Yet his conclusions are entirely based on a misunderstanding of the climate science, cherry-picked opinions (see above), and a characterization of climate scientists in general as dishonest, corrupt, and incompetent. It is quite bizarre, really, and borders on conspiracy theory. His misuse and misunderstanding of the science and lack of distinction between facts and opinion has been thoroughly documented, but people still flock to him.
This is the other end of climate science denial, and it is dangerous. The biggest threat to human existence is still us humans, which means that we can still do something about it. Perhaps that message is what people are really afraid of? Or perhaps people are sick and tired of living in a life-destroying economic system and understandably want it to end - but we don't have to end life on Earth to do that. Recently, a concerned person said to me, half-asking:
“I thought The Tipping Point had already been passed…?”
No. The good news is that there is no singular Tipping Point after which we give up and start boarding billionaire’s spaceships. The bad news is that there is no singular tipping point, and therefore no guarantee of continued status quo, nor immanent, sudden ‘collapse’. If someone tells you that The Tipping Point has been passed, they either don’t know what they’re talking about, or they are lying. Neither is good, or helpful.
Other tipping points and cascading feedbacks
That said, there is still a lot to be concerned about. A recent review paper suggests that we may already be within the starting ranges of at least five positive warming feedbacks in the climate system, which if begun and maintained, could bring catastrophic consequences to Earth’s inhabitants. This is a critically important wake-up call, and it should spark transformative change in our politics and societies- but almost no one has heard it. There is also the potential to compound the effects of one feedback loop by setting off another that is connected to it – these are called cascading feedbacks – and they can cascade into human systems as well.
Additionally, there is a paucity of research into the ‘worst-case-scenarios’ for passing tipping points and the onset of feedbacks in our Earth system. This is mostly because it requires cross-disciplinary expertise, and there is a rather strained discussion in the climate science community about whether this kind of question is useful to research at all. Most professional risk assessors however, would probably agree that an exploration of the worst possible outcomes is essential for making informed decisions about how to behave in the present. A recent paper about the worst-case possibilities is a daunting read, as it overlaps geographic areas that could be potentially worst-impacted by certain positive feedbacks, with government instability ratings and locations of nuclear capabilities. However, the authors clearly acknowledge that none of the scenarios presented are likely to happen – they are just possible, and we should keep them in mind.
The verdict
Basically, we should stop burning fossil fuels as quickly as possible.
Not ‘net-zero’ by 2050. Zero, ASAP, with broad programs that extend public services, tax the rich, preserve what is left of the living world, and redistribute wealth so that radical economic changes can be made without plunging billions of people into poverty. Because passing tipping points and beginning positive feedbacks in the climate system are not things that we can disregard, nor point to to justify inaction. As Bill McGuire, a retired Earth scientist summarizes:
“The reality is that our understanding of potential tipping points and feedback effects remains too poorly constrained for us to be confident of how severe climate breakdown will end up proving to be.”
We need to be realistic about what we face, while cultivating a science-based understanding that this is not the time to give up; it is not 'too late', and every fraction of a degree matters.