We all want positive feedback, right? Not me.
“Positive feedback” is another analogy gone astray in the corridors of corporate America. It’s come to mean simply praise. It used to refer to anything that reinforced desired behavior—praise, money, good results, whatever. But employees got positive feedback for using the term “positive feedback.” Now it’s just another overused and denatured term denoting a discrete event.
Real positive feedback is the opposite of discrete. It’s a continual, self-reinforcing cycle in which the output of a system is its instantaneous input. Real positive feedback is the mounting shriek from a loudspeaker so close to a microphone that we clap our hands to our ears and scream, “Stop it!” Left uninterrupted, the signal of compounding noise grows exponentially until the accumulated energy blows the speaker, fries the circuit, or breaks our eardrums.
Exponential compounding is why the sound begins faintly and builds slowly at first, but soon ramps up in speed and volume, as in the graph at the right. A linear build would be much easier to take, and give us a lot more time to get to the volume knob.
Courtesy of the Koshland Museum of the National Academy of Sciences, via Weather Underground
In contrast, negative feedback is something in which the output becomes input to defeat or limit a cycle. A furnace thermostat works this way. Once the temperature climbs to a certain setting, the heat causes the thermostat to shut the furnace down.
Feedback in the Arctic
For eons, the earth self-regulated atmospheric CO2 with a negative feedback that kicked in around 280 ppm, as the above graph of the Vostok ice core samples shows.
In the Arctic, positive feedback is definitely not wonderful. Excess carbon dioxide in the atmosphere traps more solar energy than the ice can reflect back into space. The natural thermostat, the ice cap, is overwhelmed by this change in atmospheric chemistry. As more heat is trapped, more ice melts; as more ice melts, less energy is reflected into space; the atmosphere retains yet more heat; and on and on.
The mounting heat is also thawing the tundra, both on land and under the now-open sea. The tundra’s vast store of trapped organic decay—the methane and carbon dioxide that’s been sequestered since the age of the dinosaurs—has started to plume up into the atmosphere, further compounding the positive feedback loop of warming and melting. Methane, of course, is a much more powerful greenhouse gas than carbon dioxide.
We may be at that upward bend in the exponential curve, the inflection point, where the ascent to the limit is very rapid.
That’s what the Arctic Methane Emergency Group thinks. At the December 5 convention of the American Geosciences Union, AMEG unveiled its position paper calling for immediate geoengineering to counter the heating of the Arctic, chiefly by spraying seawater into the sky to create sun-reflecting clouds. Otherwise, they foresee the jet stream becoming so erratic so suddenly that agriculture fails across the globe, just as in my novel, A Change in the Weather. They think 2013 is the critical year.
I’m extremely skeptical of geoengineering. The Law of Unintended Consequences casts a long shadow over the idea. It addresses a problem whose root cause is complexity (the organization of industrial society) with yet more complexity. And it means nothing unless it’s accompanied by immediate and substantial reductions in GHG output, which must happen in any case. It’s treating the symptom, not the disease. If we’re desperate enough to try it—and who decides that, by the way?—then we’re also desperate enough to make those reductions.
On the other hand, I don’t think AMEG is a bunch of science-fiction kooks. Other sober, established scientists have sounded the alarm on the imminent Arctic tipping point and the venting of methane from the permafrost. I’m waiting for public commentary on AMEG’s idea from other science organizations. Hey, NASA, NOAA, NSIDC—what do you think?
Whether we’re at the desperate stage of geoegineering or not, the situation is urgent. We could really use some positive feedback among ourselves and our leaders: more action on climate change yielding more approval and more votes, driving more confidence and commitment that we can rise to this unprecedented threat.
A Change in the Weather 