Climate Feedback Loops
Global Warming
Accelerates Global Warming
How carbon pollution is accelerating climate change.
What is a Positive Feedback Loop?
This happens when a microphone gets too close to a speaker so the amplified sound from the speaker goes into the microphone creating more sound to be amplified over and over producing the loud painful screech.
A positive feedback loop is a system where the output of the system is added to the input of the system. It is where the result of something adds to its original cause which thus accelerates the effect.
Global Warming and Bushfires
Here is how a global warming feedback loop works in Bushland and Forested areas.
More CO2 and GHG in the atmosphere leads to
Warmer temperatures which leads to
More moisture evaporation from soils which leads to
Drier forests and bushland which leads to
More bushfires which leads to
Less Carbon locked up in the Forest System and
More CO2 in the atmosphere... and so on and so on....
Once a feedback loop such as this gets started, it will accelerate by itself making it much harder to stop global warming.
Carbon Banks
There is a risk of a feedback effect occurring wherever there are large amounts of carbon locked up in a temperature sensitive system. Many forests including the crucial 'Amazon' are showing signs of drying out. (1) As we continue to lose these forests we lose the ability to stop global warming.
A solution: Bush fuel management by early burning
The Australian bush has evolved with fire. Summer bush fires or wild fires, where the bush has not been managed, emit large amounts of carbon dioxide (CO2). Research has shown that by managed burning of the fuel load in cooler months releases less carbon dioxide to the atmosphere.The carbon is kept in the soil, in the plants that survive and regenerate and in new plants that need fire to reproduce. Historically, many Australian aboriginal communities practiced management of the bush through controlled burning and there is a resurgence of this practice through a growing program of indigenous park rangers.
Here is another similar global warming feedback loop.
Melting Permafrost and
Thawing Peat Moss releases GHG's
In Canada, Alaska and Siberia, the summer period of permafrost melting has been lengthening due to the increase in global average temperatures. The local trees have evolved to stand up in the hard frozen ground. One effect is these trees fall over in the softer ground and have been called drunken trees.
More importantly, the frozen peat moss contains large quantities of CO2 and Methane gases and these are GHG's that are being released to the atmosphere. The amount of GHG's stored in the permafrost is about equal to the amount of GHG's released over the past 100 years. If it is all released, it will rapidly accelerate Global Warming making it impossible to stabilise temperatures at a level suitable for civilisation.
Here is another global warming feedback loop that operates differently.
Melting Polar Ice
Polar ice reflects 90 of the sunlight that falls on it thus reducing the amount of heat absorbed from the sun (2). As temperatures rise, the ice shelves at the poles have been shrinking in width and depth and melting in to the ocean rapidly. The ocean water around the poles is darker and thus reflects less light. It absorbs 90% of the incident light which is converted to heat. The warmer water accelerates the melting of the ice.
More CO2 and GHG in the atmosphere leads to
Warmer temperatures in the ocean which leads to
More melting of polar ice in Summer
(and less refreezing of polar ice in Winter) which leads to
Less sunlight reflected from white ice which leads to
More sunlight absorbed by the polar oceans which leads to
Warmer temperatures in the ocean ... and so on and so on....
Does it ever stop?
When feedback occurs to amplified sound, there is a point at which the system cannot produce any more sound so a new stable point is found. That state being a loud continuous screech.
With global warming, a new stable point will be be reached. (I can't quote the experts but I will look for what they predict.) My understanding is that global temperatures will stabilise at around a 6 degree Celsius increase from the usual reference point. This means there will be loss of glaciers and the water they provide to people. Ocean levels will rise significantly and massive species loss will occur. The world will be so hot, and a climate so violent and variable that it will be virtually impossible for people to live on the planet.
I expect the planet's climate will return to prehistoric conditions. I think there are some good clues to what could happen in this documentary shown on ABC 24 May 2007 Crude - The Incredible Story of Oil. You can watch this free online.
The sound engineer stops the screech by quickly turning down the amplification. Unfortunately we have no way of quickly turning down the amount of GHG's in the atmosphere.
For more info see On Wikipedia Feedback
For more info see An Inconvenient Truth
For more info see Crude - The Incredible Story of Oil
Other Effects
Global Dimming
Global Dimming has slowed the greenhouse effect. Global Dimming is the effect of less light reaching the earth as it is reflected back out into space by the particulate pollution we put in to the atmosphere. To reduce respiratory health problems such as asthma, we are cleaning up our emissions by reducing the amount of particulates released in our emissions. This is leading to a recent increase in the rate of global warming as the cleaner air has lead to more light reaching the earth.
Slightly technical notes for the critical reader:
(1) Rain is becoming more intense and redistributed resulting floods in some regions where and drought in neighbouring regions.
(2) The other reason for arctic poles being cold (as we were taught in school) is the higher angle of incidence of the sunlight and thus the greater amount of atmosphere which the sunlight travels through which weakens its power through absorption and dispersion.
Updated Jan 2008