re: #304 Ludwigvanquixote

Sal you are off base with this. Methane is a worse gas but it only stays in the atmosphere for years. CO2 on the other hand stays for centuries.

You are also right that the used to be much more CO2 in the past. IN fact, during the Jurassic Co2 levels were four times what they are today, AND WE HAD NO POLAR CAPS and much of the land we know and love today was underwater. Where did those great salt flats come from?

Right, the issue is not just that we have more and more CO2 concentration, it is that we have pumped it into the atmosphere at an insanely fast rate by geological standards and killed a huge amount of the plants that would scrub it.

This has set off any number of feedback loops. INcidently, speaking of methane, how much do you think comes out of the Siberian bog now that it is thawing?

What about reduced albedo? This is not a difficult concept, if you reflect less light you absorb more light - and get warmer because energy is conserved.

This means even more ice will melt reducing the albedo more.

Forget how to model that for a moment and accept that whatever the math is on such a process, it must exist and that by pumping higher concentrations of GHGs into the atmosphere we must be triggering these feedbacks.

We have indeed had times with no polar ice caps. We have also had Ice Ages - and much more recently. It is abundantly clear that these major fluctuations were not caused by human industrial carbon dioxide output. And indeed, co2 levels were not a leading indicator of Ice Ages, but a lagging one, as vegetation froze that would otherwise have consumed co2.

As I said before, our production of greenhouse gases must contribute somewhat to a small percentage of the warming of the ambient temperature (which was nevertheless as hot in the US as it is now in the ‘30’s before cooling for a period), but its effect is greatly outweighed by the effect caused by solar variations in the amount of radiant energy that reaches us in the first place.

The most influential greenhouse gas by far remains water vapor.