http://www.nypost.com/seven/02262007/postopinion/opedcolumnists/not_that_simple_opedcolumnists_roy_w__spencer.htm?page=0

I was asking a scientist friend about this because it was really bugging me. He pointed out that the energy emitted from the earth as black body radiation increases as the fourth power of the absolute temperature of the earth. The increased forcing from CO2 only goes up logarithmically with CO2 concentration. This means that even though as CO2 is released from the ocean, causing increased greenhouse forcing and thus increasing temperature, this is counteracted by the increased black body heat radiated from the earth. This is likely what puts the upper limit on this positive feedback, allowing a new equilibrium to be found rather than becoming an out of control feedback loop.

Cheers.

He points out that other positive feedback systems have a mechanisms that limits them. But he does not offer on this case!

The other obvious candidate is that CO2 gets sufficiently depleted out of the ocean so that no more comes out. But then you would expect the temperature and C02 to peak at the same time, not CO2 still rising for 100’s of years after temp peak.

It seems a bit absurd that something this important to the climate change hypothesis does not have an easy to find explanation.

This makes no sense. If the greenhouse effect of CO2 maxed out at the levels seen in the ice core samples, then why are we worried about adding more carbon now? We’re already well beyond the levels in the ice core, so by your explaination, already saturated.

I am so frustrated that I cannot find a good answer to this question even at realclimate. They talk about the positive feedback, but don’t explain what halts it.

It seems that with a sufficient long-term forcing, amplifying feedbacks will dominate on timescales that are important to humans. So if we allow warming to progress and the number and strength of positive feedbacks to grow, this trend may have quite a ways to run before it slows and relaxes toward something resembling equilibrium.

If we’re still be in the early stages of this process and reasonable steps can be taken against uncontrolled warming without the economic devastation predicted by “alarmists” on the contrarian side, based on ECONOMIC MODELS at best, I would prefer to err on the side of caution. We are, after all, dealing with a system with the capacity for disruptive swings given enough of a push.

And to quote J. Willard Rabett:

1. Adaptation responds to current losses.
2. Mitigation responds to future losses.
3. Adaptation plus future costs is more expensive than mitigation.
4. Adaptation without mitigation drives procrastination penalties to infinity.

There are many examples in nature of positive feedbacks that die out.

- Set fire to a forest. It starts from a cold forest, then add a small flame, it grows to a huge forest fire, burns out, goes out, goes cold. Few years later the whole thing repeats.

- Population growth – algae blooms – they start small, they grow almost exponentially, run out of food, die off.

- Spread of a disease in a population – the more people have it, the more they infect, until it burns itself out.

The same thing happens with CO2 and temperature. The positive feedback starts up, gets worse, until eventually it hits a stabilisation.

In the case of our climate it could be as simple as it is only very marginally positive, so our extra help is enough to put it into a growth mode when combined with the increase in solar influx. Take away either and that is enough to kill the positive feedback.

Or it could be that eventually it gets so hot that we become a shiny ball of cloud which cools down rapidly.

The whole of the last several million years has been a classic two state climate, oscillating between ice ages and warm periods, with sudden changes between the two. That is undisputed by anyone on any side of the debate. That is exactly the sort of situation that would be caused by having positive feedback to switch from cold to warm, and eventually a negative feedback to switch fom warm to cold.

In geological time, the balance of the system has changed several times, and just like any system can have a resonance at certain points, the climate can reach a resonant point where it is teetering between two states (our current 100,000 year ice age warm period cycle). Eventually the contintents shift or the sun changes and things settle down into a long warm or cold period.

If you look at our climate, and compare it to a machine that has a vibration problem, you hear the vibration build up and then die away, build up and die away – the big build up and die away is the hundreds of millions of years climate shift, and the individual vibrations that make up the fine grain are the 100k year switches between ice age and warm spell. (Of course, in the climate case, the whole thing is bounded by the creation of the solar system and the sun going poof and is definitely not cyclic in the billions of years timescale)

What we have right now (in my view) is an opportunity to actually control things and prevent both the positive feedback being enough to lead to rapid temperature growth, and the negative feedback being enough to cause an ice age. At least for the time being, when the continents, orbits and solar situation mean it is so finely balanced. In longer timescales, we will have to adapt, but for the next few million years its finely balanced and we can keep it just where we want it.

If people would stop bickering about it and misrepresenting the situation in either direction and look at the bigger picture then we might actually start constructively planning the climate for our future.

C02 increases from 180 ppm to 280 ppm through a glacial cycle. The CO2 changes (55%) could only explain between 0.8C to 2.4C of the temperature changes in a glacial cycle.

The temperature changes are in the order of 5C globally in a glacial cycle so add the 800 year lag to the 16% to 48% explanability of the temperature change and you get …

… CO2 is a minor greenhouse gas and does not drive the climate.