A 2008 scientific paper published in the Proceedings of the National Academy of Sciences of the United States of America considered potential “tipping points” in Earth’s climate system, arriving at a list of 15 that could suddenly and drastically change Earth’s habitability and narrowing that to a list of 9 that the authors thought could potentially happen during this century and might be prevented through public policy choices.
Tipping Point (scientific definition): A sudden transition occurring when a changing system reaches a critical point, beyond which a feature of the system becomes qualitatively different.
-The Frog’s scientific definition of a Tipping Point
An example of a tipping point is what can happen when you heat up a pot of water. At first, things seem predictable, gradual, and linear. The water just sits there kind of quietly in the pot. You’re adding heat, and the water slowly gets warmer. If you’re measuring the temperature and watching a clock, pretty quickly you can accurately predict the state of the water into the future. You can judge how much warmer it will be 2 minutes from now, for example.
But something wacky happens the moment the water reaches 212 degrees Fahrenheit (100 degrees Celsius). Bubbles start popping out everywhere in the water! The water turns into a hot gas, and starts to escape the pot and disperse throughout the room! It becomes very difficult to predict the future state of the water into the future. And, if you leave the heat on, there’s nothing you can do to stop what’s going on. The water is now qualitatively different. It’s no longer a sort of dense mass that sits quietly in a pot; it’s a chaotic, diffuse substance that’s invisible and goes anywhere it wants.
Tipping points can have various degrees of reversibility and many times frustrate efforts to bring things back to the original state. Assuming you weren’t prepared with substantial resources for the tipping point in your pot of water — with a tight lid and the ability to apply significant pressure to it and the pot — you won’t get your water back into the pot. Beyond the tipping point, it has expanded to many times its earlier volume. Even if you can quickly marshal the resources to cool the room, the water will condense back to liquid on surfaces everywhere in the room, not in the pot. You will have lost what you started with, and you won’t have any practical way to get it back.
For living things, tipping points can suddenly change the survivability of an environment in unpredictable ways. We could imagine a super-intelligent fish in our warming pot of water. Maybe it senses the water is slowly warming, but it finds that the warming is slow and predictable, and it invents and continues upgrading some technology — some sort of fishy fire suit — that protects it from the excess heat. All good. But at 212 degrees Fahrenheit, not good! Suddenly, our clever fish’s environment becomes qualitatively different! The liquid water is disappearing altogether, and everything it has learned about fishy fire suits won’t help the fish. Indeed, the influence our fish would need to exert to return things to their former state would extend far outside the pot. Poor clever fish.
Dumb clever fish, if it has also been operating the flame that’s been heating the water.
The qualitative change in water’s physical state at its boiling point is a tipping point in a simple system that we understand quite well. We observe it every time we make tea or have pasta for dinner. But scientists have come to appreciate that tipping points can exist in Earth’s much more complex climate systems. These we don’t understand well — if our species experiences one (or more) of them, it will be for the first time. They will defy easy adaptation by any of the methods we have been exercising gradually to cope with climate change.
We will be dumb clever fish in a pot.
A Nov. 28, 2019 commentary paper published in the scientific journal, Nature, updates the scientific state of knowledge of these tipping points, identifying nine planetary feedback loops that are currently active. Accounting for over half of the potential planetary “tipping points” identified by the Intergovernmental Panel on Climate Change (IPCC) starting two decades ago, the scientists warn a potential cascade among the nine active planetary feedbacks could result in out-of-control progression of our Earth to a “hothouse” state much less habitable than current conditions.
Scientists admit they have under-estimated the risks of some of these tipping points:
(While apologists for the fossil fuel industry and opponents of aggressive climate action often cite the uncertainties in climate science, we should understand that uncertainty is a two-edged sword.)
Economic models seeking to define the “lowest cost time frame” over which to transition to a sustainable energy economy have similarly been shown to have dramatically under-estimated the economic risks of delayed climate action by under-valuing what have been considered low probabilities of catastrophic consequences.
As the bar graph above shows, our assessment of the probability of catastrophe has evolved in recent years and, as we sit at about 1 degree Celsius of warming, the time for aggressive climate action is now.
This is the first post of a new series by which I plan to build a page about tipping points. The nine or so nightmares that keep climate scientists up at night wondering if, in the absence of urgent action, we might someday soon end up like dumb clever fish.
