What processes moderate our climate and prevent runaway warming?
Just that... I've no caveats, assumptions or examples to add.
2011-07-19T03:53:53Z
Thank you all for your responses. For AMP. Here is an example of 'runaway' used in the context to which I'm referring.
"The scientific community has been telling us for quite some time that we are fast reaching tipping points beyond which runaway global warming will occur which threatens the very existence of humanity" http://www.greenplanetawards.org/gwarming.html
2011-07-20T20:16:04Z
Added. Thanks for the contributions so far. So nothing apocalyptic is going to happen then? We just get a bit warmer?
Anonymous2011-07-18T15:50:10Z
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what is preventing runaway global warming? in a word. reality. global warming is scare fiction. as a group americans are the most gullible people in the world. we believe anything spoon fed to us. what a bunch of suckers we are.
For the last million years, the carbon in the atmosphere has fluctuated between 100 and 300 ppmv (parts per million volume). It was during that period that all forms of life started to evolve on Earth. Then suddenly, as the industrial revolution start, we go from 280ppmv to 390ppmv today.
This is a simplistic way to explain it without all the scientific jargon. When the sun hit the earth, the planet absorbs 50% of the heat and reverberate the other 50% into the atmosphere.
If we did not had an atmosphere, the remaining 50% would go straight in outer space and the temperature on Earth would be minus 19.
So the Co2 is an essential part of life and nature to keep the planet alive. And nature being perfect, it has determined that between 250 and 300ppmv provides the perfect equilibrium.
So what happens is, that when Earth reverberate 50% of the heat, part of it gets absorbed by the Co2 in order to keep the planet warm, and the rest is allowed to escape in outer space. But if the mass of the Co2 increase, it absorbs a bigger volume of heat before releasing the rest in outer space. As a result, the more heat is absorbed, the hotter the planet becomes. It is the greenhouse effect. You have to view the Co2 as a glass roof which does not allow the heat to escape.
As for those citing water evaporation. There are only two main things absorbing heat, C02 and water vapor. So as the heat from C02 increase and produce water vapors, the heat increase even more.
Now look at this from a mathematical point of view. You are in the 18th century. You have massive forests world wide absorbing huge amount of Co2 And you only have 1.8 billion people probably contributing 3 tons of Co2 per head of capita. Use your calculator and tell me that humanity does not contribute to Co2.
We did cut most of the forests world wide for farming in order to feed all those billion of people. And each person contribute between 6 and 27 tons of C02 a year, depending what country you live in. The average person use 8000KW of electricity per year. That's 8 tons of C02.
I suspect the first is diminishing returns. The more of a greenhouse gas that's in the atmosphere, the less effect it has. And eventually (well beyond what we're likely to end up, but there is such a point afaik) you'll reach a point of pure saturation. Other feedbacks have much clearer endpoints. For example, the ice-albedo feedback would eventually lead to an Arctic and Antarctic with no ice at all, meaning it can have no further effect on warming. (in the other direction, eventually the planet would simply be covered in ice, and thus no further feedback)
And, as several others have pointed out, the warmer a planet is, the more heat it will simply radiate away. This is the simplest of what I suspect are a number of negative feedbacks. Some of these, we may simply not have reached yet, as they will only kick in under much warmer conditions. Some (like clouds) are quite complicated, and can cause both warming and cooling.
I myself don't understand exactly what is meant by a runaway scenario. In my mind, even if the feedbacks associated with a change in forcing are great enough to overcome the diminishing returns of that initial forcing (for example, if albedo or water vapor feedbacks overcame the logarithmic growth of CO2's forcing power), there would still be a limit to the warming that could occur from that because of, at the very least, a physical limit on resource pools (e.g. as Chem Flunky said, all the ice melts). So, does a runaway warming effect mean that the warming follows a non-asymptotic (or, non-logarithmic) curve until a resource limit is reached? I think I need to read into this more myself. I've heard of Venus having a runaway greenhouse effect but I don't actually know what that means.
In any case, I think other suggestions are good ones for why we won't have a runaway effect - diminishing returns, and likely not strong enough positive feedbacks. I would assume you'd also possible have negative feedbacks that initiate and start to become dominant after some time. I'll see if I can find any more references for discussion on this topic for you.
The world has many built in carbon sinks that help moderate climate change. Limestone beds are one example, and the largest carbon sink is the ocean. As fossil fuels are burned, carbon is emitted into the atmosphere, thus producing the greenhouse effect. As oceans begin to get warmer (and they are getting warmer. The equilibrium is greatly disturbed, as evidenced by the mass die-outs of coral), the gases (including CO2) within them are released (gases absorb better at lower temperature, which is why soda becomes flat in the heat), expediting the process. The natural carbon sinks have been enough to keep the planet relatively stable over geological history, although it is true that the planet's temperature does fluctuate over time.