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Originally Posted by kirant
Not sure we can call Venus a perfect comparable. They have lots of other gasses screwing things up and has a different construct than earth. Sure, it's the closest thing to earth in our solar system, but just because it is, doesn't mean we'll emulate it well.
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I didn't mean to imply we're heading towards being Venus, just that CO2 being a greenhouse gas and its effects are significant. The composition of Venus' atmosphere is pretty well understood and it would be easy to calculate the contributions of the various gasses.
Quote:
Originally Posted by kirant
It's all about proportions though. If the house is the size of a small city, bringing in your garbage won't do much...however, if your house is a small loft, then it will.
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True, but as we can tell the portion of the CO2 in the atmosphere coming from fossil fuels is significant.
But keep in mind most of the surface of the planet is involved in the carbon cycle in one way or another so it's not so much about having a big or small house, it's more like garbage generation per square foot of your house per unit time (though of course conditions to lock up the CO2 don't always occur).
Quote:
Originally Posted by kirant
Same goes with the earth. If the water vapour is a much bigger effect in the greenhouse effect than the CO2 by several orders of magnitude, then CO2 is pretty irrelevant (though that would raise the question of a snowball effect from excess H2O in the atmosphere). However, if the effect is pretty equal, then CO2 is a major driver and we need to stop real quick.
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Water vapour has a much bigger magnitude but it also goes into and out of the atmosphere very quickly, and how much is in the atmosphere is a result of other factors, so it's not a primary driver. What water vapour does do though is magnify the effect of CO2, and CO2 when put into the atmosphere doesn't come out easily.
And you are right about snowball effects, feedback loops definitely come into play, which is why a small change can have a significant impact, and why you see jumps between one stable equilibrium and another in history as feedback loops change things significant before things stabilize.
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Originally Posted by kirant
I certainly agree it wouldn't hurt humanity to shift to something new in the course of 100-200 years. It's just I'm not sure we have the backing to state how key CO2 is in all of this yet...especially when so many reports are contradictory as to what is driving it (there are reports that say water vapour is a better way to analyze global temperature, there are some which say CO2...and the differences in ratio aren't comparable to that of combustion effects).
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Just because the mass media reports on something doesn't mean it's really that significant, there have been lots of reports (including ones on water vapour), which, just as in "climategate" the media latched onto and widely reported on, but on further analysis the report didn't actually say what the media reported, or the report itself was flawed.
"So many reports" usually ends up being one paper broadly reported on by the media vs the thousands of papers which go unreported on because they are boring (in that they simply add more support to the consensus).