Positive Feedback: Not So Good For a Warming Planet

Permafrost is one of the keys to the planet’s future because it contains large stores of frozen organic matter that, if thawed and released into the atmosphere, would amplify current global warming and propel us to a warmer world.
—Achim Steiner, Executive Director of the United Nations Environment Programme

Positive feedback and negative feedback. These are concepts that apply to many different situations: electronics, chemistry, biology, economics, and climatology are just some of them.

Negative feedbacks naturally impact on systems to help them to regulate themselves: the greater the response, the more it is negatively impacted to curtail that response. Although there are many complex scientific examples in the history of engineering of various negative feedback loops, I think a great example that everyone has in the home is the float in the back of a toilet: as the water level climbs in the back reservoir after the toilet has been flushed, the float rises along with the waterline, helping to close off the valve that allows water into the tank.

Positive feedback on the other hand amplifies the impact rather than regulating and reducing it. An example I deal with in cardiovascular medicine is the formation of blood clots. When you cut your skin and start to bleed, platelets (which are like bricks in our blood clots) become “activated” and release a bunch of chemicals to promote clotting proteins (which are like the mortar) to bind together with the platelets. These components all interact to help form the clot. But as platelets get activated, some of the chemicals released attract and activate other platelets, amplifying the response. Without this mechanism, clots would form way too slowly to prevent us from bleeding to death after any substantial injury.

Positive and negative feedbacks occur all throughout nature. So it’s no surprise they’re found in meteorology and climatology too. Negative feedbacks are good things for the planet to help maintain a consistent state, but positive feedbacks are another story. They may be good for promoting clot formation, but we’d rather not see them in our planet’s climatology.

One well-known example of a positive feedback mechanism in climatology is melting ice due to global warming. Ice at the north pole, Greenland, and the numerous glaciers found all over the planet are all slowly melting away with global warming. Ice is white and reflects a lot of sunlight; the more ice we have, the less sunlight is absorbed by the Earth’s surface, converted into infrared radiation, reflected back into the atmosphere and subsequently absorbed by our planet’s greenhouse gases. This property is referred to as albedo. But as global warming melts more of our planet’s ice, there’s a darker surface leading to more sunlight being absorbed rather than reflected back. The absorbed light energy is then converted into infrared radiation and eventually absorbed in the atmosphere by greenhouse gases leading to even more global warming and more melting ice. And so on. And so on.

Another positive feedback mechanism for global warming getting a little more attention lately results from global warming leading to the melting of Earth’s permafrost. Permafrost—that part of the soil that never gets above freezing and therefore never thaws—is found in northern latitudes all over the planet. Russia, China, Canada and parts of the US all contain permafrost. However, a new report from the United Nations Environment Programme states that much of that permafrost is now melting due to global warming, no longer permanently frozen. (Perhaps we should call it semi-permafrost.)

The problem that arises is that permafrost contains a lot of organic material in it, and that means a lot of carbon which had been permanently removed from the carbon cycle for thousands of years. Until now, that is. How much carbon, you ask? It’s estimated that about 1,700 billion tonnes of carbon is locked up in permafrost, which amounts to about twice the amount present in the atmosphere currently. Before the 21st century is up, anywhere from about 43 to 135 billion tonnes of the stuff will be released, either as carbon dioxide or methane.

This has the real possibility of becoming a positive feedback mechanism on an extremely concerning scale, leading to a runaway level of global warming heretofore unwitnessed by human beings. In other words, even if we shut down our emissions to zero tomorrow, more greenhouse gases are still going to be added to the atmosphere from melting permafrost because of the damage we’ve already caused. And don’t forget that methane—which will play a major component of the greenhouse gases released from permafrost—is more than twenty times as potent a greenhouse gas compared to carbon dioxide.

This raises even greater concern because UN projections have largely failed to take into account the effects of melting permafrost when predicting future global warming trends. In other words, current projections will be too conservative, possibly leading world leaders to believe there’s less of an urgent need to take action than there really is. (As if they needed any other excuse to remain passive on the subject, apart from the platitudes they espouse at annual climate talk summits.)

Some of this gets scary at times, and I must admit when I learn about things like this, I truly fear for our planet’s future. But rather than throw in the towel and give up the fight, it gives me even greater resolve to work harder still at educating people about this issue.

We all have to do whatever we can to make a difference in this problem. Otherwise our grandchildren and their grandchildren will never forgive us.


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