As global warming gets worse and worse, something threatens our species that even most climate activists don’t seem to understand. It’s a phenomenon known mainly to engineers and scientists. It goes by the name of “positive feedback.”
Perhaps it’s poorly named. In planetary heating, there’s nothing “positive” about positive feedback. At least five known mechanisms of positive feedback can accelerate planetary heating even if and after we stop burning fossil fuels entirely.
In other words, positive feedback may already have made planetary heating self-sustaining. It may have created multiple “tipping points” that put acceleration of planetary heating completely beyond human control. So in terms of human comfort, health, happiness and survival, “positive” feedback is nothing but negative.
What is “positive feedback”? It’s any phenomenon by which physical or chemical forces reinforce themselves so as to “positively” increase their own strength and magnitude, i.e., to cause them to grow “automatically” and inevitably, as a consequence of known cause and effect.
Most familiar to non-scientists, at least those of a certain age, is amplifier screech. In the old days before everything went digital, you would get an instantaneous screech from speakers fed by an electronic amplifier whenever you put the microphone input too close to the speakers. People my age can remember this sort of thing happening at dances, concerts and other public gatherings quite often. If doesn’t happen much now because digital circuitry, which acts far faster than any human reflex, cuts the sound blast off, using deliberately designed negative feedback.
Like amplifier screech, all positive feedback is nonlinear. It increases astonishinigly rapidly. It simply doesn’t obey the laws of arithmetic or “common sense.” For more common examples of positive feedback in ordinary life, click here.
So what are the main mechanisms of positive feedback in planetary heating? Here are the top six, in roughly descending order of their probable threat to human survival:
1. Wildfires. This is a “new” source of positive feedback, and probably the most dangerous. It’s not new in concept, but new to human experience and understanding in connection with planetary heating.
Don’t believe this? Well, think back in recent memory. It’s only been in the last five years or so that anomalously big, unexpected, and globally widespread wildfires have hit us. This past summer they happened all over Canada, polluting our densely populated American East Coast and Upper Midwest with smoke. At the same time, big fires devastated Greece and Spain. The last summer Down Under, they devastated Australia. In previous years, they hit Belgium, France, and Russia, including near Moscow and even Siberia.
Big wildfires boost planetary heating with positive feedback in two ways. First, their burning itself turns trees and vegetation into carbon dioxide, as well as polluting smoke. Carbon dioxide is the principal greenhouse gas that we humans produce and which causes global heating. But wildfires produce it without our conscious effort or any collateral benefit to us.
Second, by destroying trees and other vegetation as living organisms, wildfires remove one of the biggest natural “sinks” of carbon dioxide, namely, the organic growth of wood and vegetable matter. Growing trees and vegetation fix carbon dioxide and release oxygen through photosynthesis. Stopping their growth by burning them up reduces that “sink” of carbon dioxide. In addition, wildfires minutely damage the balance of oxygen and carbon dioxide in our atmosphere that lets us breathe. Planting new trees can help increase the magnitude of photosynthesis, but it takes many years for a seedling to grow to the size and photosynthetic capacity of a mature tree.
None of our scientific-mathematical models that we use to predict global heating accounts for this positive-feedback effect of wildfires. Why? It’s too new, and it’s too hard to predict. Wildfires depend on two hard-to-predict heating phenomena: the local drying of trees and vegetation through heating and low humidity, and the random starting of wildfires by natural lightning. (Wildfires started by power lines downed by high winds are equally hard to predict.) Climate scientists have simply been caught flat-footed by the magnitude and speed of this “new” type of positive feedback.
2. Melting permafrost. As our planet warms, it’s not just ice in glaciers that melts. It’s also something called “permafrost.”
Permafrost occurs mostly in the near-polar regions of the Northern Hemisphere, including the frozen tundra of Alaska, Canada, Scandinavia, and Russia (Siberia). It contains the frozen remains of ancient, decayed vegetation. That frozen, decayed mass includes a lot of methane, trapped inside the physical and molecular structure of the frozen tundra.
As the whole mess melts, it releases methane in the permafrost into the atmosphere. And methane, in the short term, is eighty times as powerful a greenhouse gas as carbon dioxide. That means that, gram for gram, methane causes eighty times the planetary heating of carbon dioxide, at least until it gets absorbed or destroyed by natural processes.
There’s yet another way melting permafrost boosts planetary heating without us burning any fossil fuels. Permafrost contains frozen cavities and caverns of mostly methane, in gaseous form, which gets released into the atmosphere when the permafrost melts. We only recently discovered this phenomenon, so it doesn’t appear in any of our climate models.
While all these melting-permafrost phenomena are well understood and rock-solid science, their magnitude is far from known. Why? Because they occur in remote, sparsely populated and poorly studied places on the globe. We know these things are happening; we just don’t know precisely where, how much or how fast. So naturally they don’t appear in any useful quantitative way in the climate models we use to predict planetary heating.
3. Dissociating deep-sea methane hydrates. This phenomenon has much the same effect as melting permafrost: releasing free methane into our atmosphere. Deep in the Earth’s oceans, in the cold and dark and under the immense pressure of thousands of meters of seawater above, water molecules form little “cages” that contain methane molecules inside. As the water around them warms with planetary heating, those little cages can disassociate, releasing free methane to rise to the surface and into our atmosphere.
This phenomenon is real and happening. But it’s very hard to know how much and how fast. Why? The deep oceans are the hardest places to study on Earth, and they are in fact the least studied. We can hardly establish a network of global observation posts down where water pressure can crush titanium vessels.
We do know that temperature on the surface of our oceans is rising rapidly, far more than we expected. But scientists have little idea how quickly the temperature in the deep oceans is rising and where. So this deep-sea phenomenon, although perhaps catastrophically dangerous, may be the biggest wild card in climate science.
4. Melting (water) Ice. When glaciers and sea ice melt, they have two positive-feedback effects. The first and simplest is removing a big heat sink.
Readers who remember their high-school physics know that ice has a “latent heat of melting” of eighty calories per gram. What this means is that it takes eighty calories of heat to melt a gram of ice. After it melts, that same eighty calories, applied again to that same gram of water, will raise its temperature to eighty degrees Centigrade, or 176 degrees Fahrenheit—nearly the boiling point of water. (This relationship of one calorie to heat a gram of water one degree Centigrade is how a calorie is defined.)
So as naturally-occurring ice melts, it removes a big heat sink from our oceans, glaciers and mountains, allowing the resulting water to heat faster as a result of other sources of planetary heating. This source of positive feedback is well understood and included in climate models.
5. The “Albedo” effect. When glaciers melt, the highly reflective (and usually white or mirror-like) surface of terrestrial ice turns to a less reflective brown, green or blue of earth, vegetation or open water. The resulting surface, whether land or water, is less reflective of both heat and light. Therefore, the less ice there is on the Earth’s surface, whether land or water, the less heat and light from the Sun get reflected back into space, and the more they heat the Earth. This source of positive feedback is also well studied, well understood, and included in most climate models. (The “Albedo” is a technical measurement of the reflectivity of a lunar or planetary surface.)
6. Social positive feedback. Although some are hard to quantify and therefore hard to include in climate models, all of the foregoing phenomena are well-understood and unquestionable matters of physics, chemistry, and/or biological science. But this essay would be incomplete without noting the existence of other undeniable sources of positive feedback: the social and political ones.
The most casual observer of humanity today must conclude that human society, globally, is beginning to fall apart under the stress of planetary heating and its consequences. The so-called “post-war global order” is dissolving, and democracy is under siege worldwide, including here in the United States. Mass migration is exploding, as desperate people from the global “South,” driven in part by crop failures, drought, and summer surface temperatures reaching the limits of human survivability, seek the more habitable spaces of the Earth’s temperate zones, even the erstwhile frozen reaches of Canada.
As the global order decays, the risks of war are increasing rapidly. In fact, we already have the most brutal and atrocious war since World War II or Vietnam, in Ukraine, the heart of Europe, with no end in sight.
Wars and the increased risk of wars have two positive-feedback effects on planetary heating. First, they incentivize the rapid extraction and overuse of fossil fuels because fossil fuels are the primary source of energy for war-fighting machines worldwide. As nations build up their arsenals, they commandeer and (in the market) bid up the prices of fossil fuels even as they build the war-fighting machines that use them. So petro-states like Russia and Saudi Arabia double-down on their extraction of fossil fuels to exploit that source of income and wealth while they still can. (The least polluting forms of fossil fuels, oil and gas, are running out, albeit on times scales of decades or so after planetary heating is likely to decimate us.)
The second source of social positive feedback is more subtle. Nations under stress—or even those that think themselves under stress, like China, Iran, North Korea and Russia—devote more and more of their resources to military planning and hardware, and to handling (or rejecting) the masses of immigrants that planetary heating drives to their borders. They devote less and less resources to making the transition to renewable energy that is essential to reducing the acceleration of climate change.
With these points made, readers themselves can discover yet other mechanisms of social positive-feedback in planetary heating. For example, as the planet warms, “southern” diseases like tuberculosis, malaria, Zika and West Nile fever migrate north, potentially producing endemics or pandemics in nations once thought to be immune from these maladies. Devastated or threatened by unfamiliary diseases, those nations devote more resources to fighting disease and fewer to their energy transitions.
The result of these social phenomena is, in many ways, a reduction in resources and effort applied to fight planetary heating. They retard the application of human ingenity and wealth to wean our species from the fossil fuels which lit the fuse that threatens to ignite a self-sustaining climate bomb.
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All six mechanisms of positive feedback in planetary heating are real. The first five are hard science; the sixth is evident to anyone who can see cause and effect. But of all the six, only the fourth and fifth have been well quantified and are included in current climate models.
Two logical conclusions are inescapable. First, our current climate models—all of them—err on the side of caution. Perhaps they err grievously; we have no way of knowing.
So our current climate models likely underestimate both the speed of heating and the extent to which it can become self-sustaining, even if and when we humans stop burning fossil fuels entirely. Note that none of these positive-feedback phenomena, except the last, “social” one, has anything directly to do with fossil fuels. All the others are “natural” phenomena that proceed automatically, as a matter of scientific cause and effect, regardless of any human act or intervention.
The second conclusion is even more dire. Together, these six positive-feedback phenomena have the potential, but not the certainty, of causing runaway, self-sustaining planetary heating regardless of anything we humans do or don’t do from here on out. Our global environment may be on an autonomous path to a new steady state, decades or mere years hence. That new state may mean temperatures and weather patterms we can only guess at now, but which somehow we must survive.
If we were an intelligent species, as we deem ourselves (“Homo sapiens”), wouldn’t these facts cause us to redouble our efforts to stop burning fossil fuels, and to make doing so our species-wide top priority? Besides geo-engineering, the only thing we can do to change the ultimate climate outcome is make the transition from fossil fuels as quickly as possible, leaving most of the rest of them in the ground.
Besides possibly reducing the permanent damage to our species caused by the ultimate steady-state planetary climate, there is yet another benefit. The solar farms, windmills, geothermal plants, hyroelectric plants, batteries, and smart grids that we build will not become useless stranded assets, like all the extraction and refining plants, pipelines, tankers and other transport means, when gas and oil run out.