Amplifying Feedback

Amplifying Feedback  in our Climate System

Amplifying feedback is an important feature of our climate system.  For example  in the Arctic where warming of the Arctic is causing further warming.

Diagram: The Arctic Ice Feedback Cycle
Diagram: The Arctic Ice Feedback Cycle

The Arctic warms, the Arctic ice retreats, less sunlight is reflected so the ocean absorbs more of the sun’s rays, so the Arctic warms further.

Going through this again in more detail, this is an amplifying feedback loop in which: (1) an increase in temperature melts ice, decreasing the area covered by sea ice and so increasing the area of exposed ocean. (2) This decreases the reflection of sunlight, as ice is far more reflective than the newly exposed ocean. (3) This reduced reflection increases the sunlight that is absorbed by the ocean. (4) This increases the temperature, amplifying the original increase in temperature and melting more ice so the cycle tends to repeat.  (This is discussed in more detail on the page:  Evidence > Arctic Ice )


Other examples of amplifying feedback:

  1. A person says “hello” into a loud-speaker, and this kicks off a soft hum, which rapidly escalates into that ear-piercing shriek called feedback.
  2. Something  decays, like paint on a building: the more the paint cracks, the more moisture gets under the paint, and the faster the paint cracks. Amplifying feedback can destroy things.
  3. Something emerges,  like a new interest: something catches your interest, so you investigate it more, and become more interested, and turn it into a career.  Amplifying feedback can create new things.

Amplifying feedback is happening when:

  • a change,
  • leads to more of that change,
  • which leads to more of that change …

It can start with a change so small that you cannot notice it.  The small initial change can be amplified by a repeating sequence of events.


Danger: The Amplification of Global Warming

The risk of allowing the current warming of our planet to continue, is that feedback cycles which amplify the current global warming will become dominant.  They could producing run-away warming, which would continue even if humans stopped burning all fossil fuels.

When a loud-speaker goes into “feedback”, you can quickly turn it off.  Unfortunately, the earth’s climate does not have an off-switch.

We have co-evolved with our climate, so our current climate system suits human beings and the rich diversity of life on our planet.  We need to protect our current climate system because:

  • The amplification of global warming threatens to destroy our current climate, and
  • We do not know what climate system could be created by this amplification of warming.  It could be radically different.  It could be too hot for humans to stay alive.

Here are some other climate feedback processes that could amplify the current warming:

Methane release from permafrost

There are vast quantities of methane trapped in the Arctic permafrost.  The carbon in this methane is about twice as much carbon as the carbon that is now in the atmosphere.  Permafrost is ground that is normally permanently frozen. But climate change has caused permafrost to melt at an unprecedented rate. The ground buckles and sinks, causing trees to list at extreme angles.
(Drunken Trees: Signs of Climate Change: National Geographic: Broken Link)

Fallen trees after the permafrost melted in Fairbanks, Alaska in 2004 (National Geographic)
Fallen trees after the permafrost melted in Fairbanks, Alaska in 2004 (National Geographic)

Thawing permafrost can cause worrisome damage to forests, buildings, roads and sewerage.  It also releases methane that is trapped in the ice, adding to the greenhouse gases in the atmosphere.  This can form an amplifying feedback cycle.  Methane is about 25 times more potent as a greenhouse gas than carbon dioxide.

(A Thawing Rotting Arctic: US National Snow and Ice Data Centre NSIDC)

This diagram shows how warming can lead to more warming.

Diagram: The Methane Release Feedback Cycle
Diagram: The Methane Release Feedback Cycle

In this amplifying feedback cycle: (1) an increase in temperature melts permafrost. (2) This releases methane. (3) This increases the greenhouse gases in the atmosphere. (4) This increases global temperatures, amplifying the original increase in temperature and melting more permafrost to continue the cycle.
Arctic soil thaw may unleash runaway global warming (Scientific American, 2008)

Methane Release from under Cold Sea Floors

There are even more vast quantities of methane held as “methane hydrates” under cold sea floors.  There could be more carbon in these methane hydrates than the carbon in our entire coal, oil and natural gas reserves.

The current warming of our planet could lead to the destabilisation of these hydrates and the release of this methane leading to another feedback of warming leading to further warming.

“Billions of tonnes of the greenhouse gas methane are trapped just below the surface of the East Siberian Arctic shelf. Melting means the area is poised to deliver a giant gaseous belch at any moment? – one that could bring global warming forward 35 years and cost [the global economy] the equivalent of almost a year’s global Gross Domestic Product”
Arctic release of methane could cost $60 trillion (New Scientist, July 2013)

The current warming could lead to methane release dominating our climate, with spiralling global warming, even if humans stopped burning all fossil fuels.

Warmth Amplifying Feedback Cycles

This site has detailed the amplifying feedback cycles formed when warming leads to:

  • Melting of Arctic ice, leading to reduced reflection of sunlight, leading to further warming.
  • Melting of Arctic permafrost, leading to the release of methane, leading to further warming.
  • Destabilisation of sea floor methane hydrates, leading to the release of methane, leading to further warming.

Unfortunately, there are many other warmth amplifying feedback cycles, such as :

  • Warming increases the melting of the surface of the Greenland ice sheet.  This increases the amount of dark-coloured dust on the surface of the ice.  (This dust originally fell onto the glacier and was contained in ice before the ice melted.)  This reduces the reflection of sunlight.  This leads to further warming.
  • Warming contributes to forest destroying fires.  This reduces the consumption of CO2 by forests.  This increases CO2 in the air.  This leads to further warming.
  • Warming leads to warmer oceans.  This increases areas of nutrient poor sea surface.  This decreases the algae population.  This decreases their draw down of CO2 .  This increases CO2 in the air, leading to further warming.

Links


There may not be any climate dynamic that effectively resists  the current warming

James Lovelock’s book, “The Revenge of Gaia” ( 2006, p 35) identifies a couple of climate dynamics that might be able to limit temperature increase, stating that we don’t know enough about these processes.

Lovelock is concerned by the observed rate of global warming.  This suggests that there is NO global climate dynamic that will limit temperature increases, and so retain a climate  that is safe for life as we know it.

Lovelock notes that the current levels of methane and CO2 in the atmosphere are comparable to that caused by natural releases of these gases fifty-five million years ago. At this time, temperatures rose between 5 and 8 degrees C, with consequences lasting 200,000 years.

We do not know whether a climate dynamic will emerge to limit temperature increases to a safe level. This is one area of  scientific uncertainty.

There are many amplifying feedbacks that could cause runaway climate change. They pose a real risk for the global economy, political stability, human health and our environment.


Stop the juggernaut of climate change while we can

Particularly the retreat of the Arctic  sea ice is a clear sign that the juggernaut of climate change is picking up speed.

No Problems
No Problems

We need to leap for the brakes before we reach a cliff edge.  We need to reduce green-house gasses in the atmosphere before a tipping point where some amplifying feedback cycle becomes dominant and leads to unstoppable, run-away warming.


Feedback is a well established concept

If feedback is a new concept for you, you might be wondering whether it is some new-fangled, wonky concept.  It is not.

Feedback is a long-established concept that is a central part of “Systems Theory”.

You may know about amplifying feedback under other names, like:

  • Positive feedback loops
  • Vicious cycles
  • Virtuous loops, or
  • “Deviation amplifying mutual causal processes”,  which is what Maruyama called it in his revolutionary 1968 article on feedback

(Maruyama: 1968: The Second Cybernetics: Deviation Amplifying Mutual Causal Processes)

Negative Feedback

While amplifying feedback loops tend to change systems, negative feedback tends to prevent change.  See the above Maruyama article or Wikipedia.
https://en.wikipedia.org/wiki/Negative_feedback


Feedback Reigns

The importance of amplifying feedbacks led to the name of this web site: “Feedback Reigns”

Updated: 21 May 2018

 

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