Wednesday, February 1, 2012

Of Feedback Loops and Tipping Points, and Cabbages and Kings

The sea was wet as wet could be,
The sands were dry as dry,
You could not see a cloud, because,
No cloud was in the sky,
No birds were flying overhead,
There were no birds to fly . . . . .


One of the most frightening aspects of global climate change is the triggering of natural feedback loops. These loops begin with a natural process which is in a stable condition that can be destabilized by inputs beyond the usual levels found in nature. Once stability is compromised, the resultant outputs feed back as inputs and accelerate the instability until a "Tipping Point" is reached and an unstoppable, runaway condition is created.

A good analogy would be a young child anchoring an open boat in a still pond and then placing a single pebble in the bow section of the hull each day. During the first few months or even years, little if any visible effect would be detected. As time went by and the total mass of the pebbles grew, the change in aspect of the boat would become more apparent.

A boat design feature called reserve buoyancy would provide greater resistance as the instability grew but this would bring only temporary relief to allow time to re-balance the boat. At some particular mass of pebbles, the tipping point would be reached, the bow dip below the water's surface, water pour in at an accelerating rate and the boat would sink.

Depending on the size and design of the boat, and the size and specific gravity of the pebbles, this might take a lifetime or the task might even need to be passed on to another generation but, as long as the input of pebbles continued unabated and no offsetting process was initiated to re-balance the system, the boat would eventually sink.

Below are just three probable climate change feedback loops, these are having an effect already   —   there are more being identified:

Melting of Arctic Sea Ice

Warming of air or water causes a decrease in the average area of annual sea ice cover in the Arctic along with a corresponding decrease in albedo. Albedo is the fraction of solar energy reflected from the Earth back into space. It is a measure of the reflectivity of the earth's surface. Ice, especially with snow on top of it, has a high albedo; most sunlight hitting the surface bounces back towards space. Water is much more absorbent and less reflective.

So, if there is a lot of open water, more solar radiation is absorbed by the ocean than when ice dominates. This extra energy absorbed by the water increases its temperature and further decreases the area covered by ice, thus fueling the feedback loop.

With information from - Earth & Space Research

Thawing of Permafrost

"Permafrost contains carbon, accumulated from the decomposition of plants and animals over tens of thousands of years. Last September, researchers at the University of Florida estimated that more than 1,800 billion tons of carbon are stored in northern permafrost—twice the amount in the atmosphere today. In its frozen state, organic matter decays very slowly. But as the temperature rises and permafrost melts, the material breaks down rapidly, releasing carbon into the atmosphere."

"When organic matter degrades in dry air, carbon dioxide is emitted. And in wet soil or underwater, where there is little or no molecular oxygen, anaerobic bacteria break down the organic materials and give off methane. Both CO2 and methane are greenhouse gases [methane much worse than CO2]. As they are released into the atmosphere from permafrost, scientists predict that a disastrous cycle will emerge: The gases will trap hot air, raising the air temperature and melting the permafrost, releasing more carbon and further heating the planet [in a classic feedback loop]." - Popular Science

Carbon Sinking Capacity of Canada's Boreal Forest

"Scientists have identified the 1.2 billion acre Canadian boreal forest as the largest intact forest and wetland ecosystem remaining on earth. Rivaling the Amazon in size and ecological importance, Canada’s boreal supports the world's most extensive network of pure lakes, rivers and wetlands and captures and stores twice as much carbon as tropical forests. It teems with wildlife — including billions of migratory songbirds, tens of millions of ducks and geese, and millions of caribou. The Canadian boreal is an irreplaceable global treasure."

"Tree mortality due to regional drought in the western Canadian portion of the boreal forest grew at a rate of 4.9% per year from 1963 to 2008. Drought and warmer temperatures brought about by climate change has increased the extent of outbreaks of beetle and insect infestations which can contribute to tree mortality. Drier forests adds to increasing wildfire frequency, intensity and size which releases carbon and affects the forest's capacity to regenerate."

"Such interactions among climatic warming, ecosystem disturbances and forest responses represent potential positive feedbacks that could dramatically alter future carbon sink-source relationships in boreal forests. If this tree mortality continues to increase more rapidly than growth in response to climate change, this will reduce net forest growth, transform Canadian boreal forests from a net carbon sink into a large net carbon source, [triggering a feedback loop]." - Indybay

. . . . . "O oysters", said the carpenter,
"You've had a pleasant run,
Shall we be trotting home again?"
But answer came there none,
And this was scarcely odd, because,
They'd eaten every one.
Lewis Carroll - "The Walrus and the Carpenter"
(from Through the Looking-Glass and What Alice Found There, 1872)

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