[kirant]

Originally Posted by photon

True, but as we can tell the portion of the CO2 in the atmosphere coming from fossil fuels is significant.

Limiting ourselves to CO2, yes. Again though, it's a matter of how much the CO2 acts in relation to all the GHGs in the atmosphere.

Originally Posted by photon

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).

Of course. I was just trying to keep the garbage coming in constant.

What you say is correct though. It's a matter of how much we're generating per unit of time, not per area.

Originally Posted by photon

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.

I wonder though how much of the changes are from the natural and how much from the human. We've seen real fast changes historically, and some around the speed of today (to the "fireball" earth, I think we saw much faster increases...if you trust the studies on the billions of years old temperatures).

On a bit of a tangent is exactly what influences water has. Commonly accepted is that it's a feedback that magnifies the running of CO2. However, it's also noted that vapour and clouds in the atmosphere act as a good reflection source of new incoming radiation (terrestrial albedo was it?).

If we assume both are true and minimal outgoing radiation by the earth, we get that we retain a lot of the old radiation inside our local system and less coming in...which would imply we hit a maximum at some point if we assumed 100% reflective. However, that won't happen. Of course, the interaction of these two parameters are what will drive everything, if true. Though it can be safe to say that our earth won't ever hit 1.0 in reflection.

Originally Posted by photon

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.

I understand that. I usually wait until media dies down and peer review is completed to see if there is any real backing to the argument first.

Originally Posted by photon

"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).

Of course. I'm not going by media though. I'm going by the academic world (which, of course, has its own media set up, leading to similar issues!) and discussions with a climate change prof whom I still talk to.