Originally posted by Yarcofin
You're still ignoring my mention of the earth's oceans, which give off massive amounts of both CO2 and water vapour
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Didn't realize I was ignoring, let alone still ignoring.
Water vapor is not considered as climate "forcing" because the amount of H2O in the air varies basically as a function of temperature.
As the Earth warms due to other greenhouse gasses the H2O increases due to evaporation.
It isn't water vapor spewing out of coal plants or SUVs it is CO2.
Increased Water Vapor is not the cause of Global Warming it is a symptom and an accelerant.
mustelid.blogspot.com...
Water vapour is not the dominant greenhouse gas
OK, so it may not surprise you that I'm going to have to qualify the headline a bit lower down, but the point itself remains.
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In contrast, CO2 has a long lifetime (actually calculating a single "lifetime" for it doesn't work; but a given CO2 pulse such as we're supplying now will hang around for.. ohh... a century or more). It doesn't rain out (amusing factoid: the surface temperature of the deep interior Antarctica in winter can be colder than the freezing point of CO2; but this doesn't lead to CO2 snow (sadly, it would be fun) because the freezing point is lower because of the lower pressure because its higher up). So if you put in extra CO2 the climate warms a bit; because of this move WV evaporates (it doesn't have to, but just about all models show that the relative humidity tends to be about constant; so if you heat the atmos that means that the absolute humidity will increase). This in turn warms the atmosphere warms up a bit more; so more water gets evaporates. This is a positive feedback but a limited one: the increments (if you think of it that way) get smaller not larger so there is no runaway GH effect.
So: adding CO2 to the atmosphere warms it a bit and ends up with more WV. Adding WV does nothing much and the atmos returns to equilibrium. This is why WV is not the *dominant* GHG; its more like a submissive GHG
www.realclimate.org...
Water vapour: feedback or forcing?
Whenever three or more contrarians are gathered together, one will inevitably claim that water vapour is being unjustly neglected by 'IPCC' scientists. "Why isn't water vapour acknowledged as a greenhouse gas?", "Why does anyone even care about the other greenhouse gases since water vapour is 98% of the effect?", "Why isn't water vapour included in climate models?", "Why isn't included on the forcings bar charts?" etc. Any mainstream scientist present will trot out the standard response that water vapour is indeed an important greenhouse gas, it is included in all climate models, but it is a feedback and not a forcing. From personal experience, I am aware that these distinctions are not clear to many, and so here is a more in-depth response
Regarding CO2 from the oceans.
The ocean is responsible for 80% of the carbon dioxide on Earth.
Where does this stat come from?
To my knowledge the oceans absorb CO2 not emit it.
www.harvardmagazine.com...
Of all the carbon dioxide (CO2) emitted into the atmosphere, one quarter is taken up by land plants, another quarter by the oceans.
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Another process, called "the biological pump," transfers CO2 from the ocean's surface to its depths. Warm waters at the surface can hold much less CO2 than can cold waters in the deep
Any CO2 coming out of the ocean comes down in rain as the "fertilization effect"
Its effect is to pull carbon out of the upper ocean and cause it to rain down into the depths, where bacteria and other organisms metabolize and release it back into the water as CO2, enriching carbon dioxide in the deep ocean.
Oceans are natural carbon dioxide sinks.
en.wikipedia.org...
A carbon dioxide sink or CO2 sink is a carbon reservoir that is increasing in size, and is the opposite of a carbon "source". The main sinks are the oceans and growing vegetation. The concept has become more widely known through its application by the Kyoto Protocol.
