Tuesday, September 25, 2007

On flipping and precaution

Since the world is full of ignorant people that don't understand Swedish, I will try to stick to English.

A very common feature of complex systems (e.g. organisms, ecosystems, the ecosphere, economic systems) is the habit of nonlinear changes. That makes their behavior extremely hard to predict. If you are inside such a system, e.g. a climate
system, they are easy to interpret as stable or predictable.
You make a complicated calculation and come to the conclusion that the temperature (or sea level, or any other characteristic of the system) will change, say, 1% within 100 years. The only thing that can be said
safely of such a calculation is that it is wrong. Complex systems don't change in that way. They flip, i.e. they suddenly change into another state that can not be calculated from the knowledge of their current parts.

Two typical ways of flipping in a complex system. The upper is a 'bifurcation', the system changes into one of two alternate stable states (e.g. a climate changing into a new heat period or a new ice age) the lower is a 'catastrophe' (e.g. a stripped ecosystem that changes into a desert). The main issue is that, after flipping, there is no way back, even if the original variables are restored.

If you live within the system, before the flip, you are unable to predict the flip. You may be able to predict that a flip will come, but not when, because there are very few signs from within that the system will make an abrupt change, and how.
If you live in, say, the upper system, some way from the place when the system is so strained that it will bifurcate, you can not tell when the bifurcation will come, because there are no signs of it.

The most beautiful (and recent) example of a climate bifurcation was the change into Younger Dryas about 12000 years ago, when the climate of the Northern hemisphere changed from a warm-moist climate into a cold-dry in a period of less than ten years. It lasted about 1300 years, delaying the start of the current interglacial period.

Possible flips
There is a multitude of possible climate flips. Most of them are interacting with each other, making the overall effect highly unpredictable. Examples are such as the calving of the Ross-ice, the loss of the Gulf stream, the thawing of the polar tundra, emitting methane, the loss of the Arctic polar cap. All of those are non-linear changes, unpredictable until they start, almost impossible to revert when they start.

Run up by the scientists
This blog was written in September 2007. Already in Februay 2008, it has become an official truth.
Read the article in Independent.

What can we do?
Treat climate flips as a pack of lions on the savanna; chose another path that leads away from them. Currently, the widest path that leads into a climate flip is the emission of of ghg, notably carbon dioxide. But, as in the case with the lion pack, it is senseless to go slower into the pack (equivalent of emitting less carbon dioxide), you have go backwards, i.e. you have to diminish the carbon dioxide cloud. I.e. reduce it by more than you emit.
Ceterum censeo: You have to bind carbon (in the form of charcoal) at a faster rate than you emit carbon dioxide.
Otherwise it is like standing there, looking at the lions, until they get hungry.

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