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Comment by BurningFrog | Hacker News Reader

OK, so there are some positive feedback loops for global warming. As temperature rises, that causes other effects that in turn warms the climate even more.

But I can't see any fundamental reason that such side effects should add to the warming. It seems just as likely that they would counteract it. It's not like there is any plan behind it. In Physics, whatever happens happens.

So... I wonder if there is also a set of counteracting global warming side effects that don't get reported much, since that isn't scary? Or is there some fundamental reinforcement mechanism here that I'm not seeing?

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There are but they operate over really long time periods, tens to hundreds of thousands of years. The balance is naturally restored through an increase in weathering rates (which are a function of of the CO2 concentration in the atmosphere). The rate at which we are pumping carbon is unprecedented for at least the past 66 million years. There's no natural mechanism which could restore the balance fast enough. I have a PhD on this topic, I investigated climate change and climate evolution in deep geological times in order to find a proxy to what's happening today. The closest thing that ever happened in the past 66 million years is the PETM (see my other comments in this thread). I'll be glad to any questions that you might have.

The biggest negative feedback loop I am aware of is clouds. Higher temp, more moisture in the air, more clouds, greater reflection of incoming light (and greater retention of heat, so not a clear negative loop in all scenarios). However, as far as I can tell, clouds are a lot easier to model than the positive feed back loops we know/suspect, albedo decrease, clathrate guns, peat breakdown, etc. Thus, we are in a situation, where negative feedback loops seem well accounted for and there are a few potentially catastrophic, but perfectly plausible, positive feedback loops that are too difficult to properly assess. It is scary.

Are you sure clouds actually reduce warming? My understanding was that since they retain heat through the night, but only reflect light in the day, they actually exacerbate warming. That's why it's thought that airplane contrails contribute to warming, since they increase cloud cover. Could be wrong though; I don't recall where I read that exactly.

There's no reason that feedbacks must be positive in principle. Regardless, though, as the earth system wanders farther from its most recent stable state (the Holocene equilibrium), its behavior is likely to continue to become more chaotic and difficult to predict. That's not good for humans no matter whether it involves warming or cooling.

To my knowledge the reinforcement mechanisms we are aware of do tend to be positive, though, hence the focus on warming.

It's not fundamental, but it makes the whole situation less predictable and extreme scenarios (both good and bad) far more likely.

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