> 10 meters high layer of CO_2 with current concentration already absorbs 99,94% of IR radiation, so whatever made it above fourth floor would be swallowed by next floors. Any change to the concentration of CO_2 makes no difference on Earth's radiation.
Do you have a source for this?
>Water is even more potent
Yes and that would be a huge problem if it built up instead of falling out of the sky.
>how are you sure that Sun's increasing activity is not the reason of climate change?
This is actually what I was thinking of when I said "we don't know for certain is if there is another currently unknown cause with a larger contribution to global warming" though I believe this particular theory has been debunked.
>four centuries ago Batic Sea was freezing seasonally
You are referring to the little ice age which was primarily a localized event and therefore not caused by changes in the greenhouse effect or solar radiation.
http://en.wikipedia.org/wiki/Little_Ice_Age
>We know it is highly correlated, true. Correlation is not causation, though.
I completely agree. The fact that they are correlated does not give us a causal link. The fact that green house gasses increase temperature does. The only missing piece here is how much of the increased temperature is caused by our greenhouse gas emissions and how much is caused by other unidentified forces.
>There are plenty of possible effects in thermodynamics that would easily make the noise in measurements above the level of changes that are announced for greenhouse effect.
I completely agree. When I said there could be an unknown effect, I did not mean to imply such an effect would be outside of "possible effects in thermodynamics".
>We have no way to verify the claim the greenhouse effect takes the place
Actually we can. We can measure the radiation before it hits earth, when it hits the ground and when it leaves the atmosphere as well as measure what radiation is absorbed and emitted by various gasses. We don't have a perfect understanding of the green house effect, but we can observe it in action.