Global Warming, CO2 0.0381% of Earth's Atmospheric Gases

I have debated this issue many times. I always ask supporters of the greenhouse gas theory one question:

"Where is the hard science on climate sensitivity?"

So far no one has come up with an answer to this.

We all know that CO2 has a warming effect. All you have to do is blow on your hands on a cold day to see this. But in the context of the earth's atmosphere, HOW MUCH warming effect does it actually have? That is the question of "climate sensitivity."

It is usually expressed in terms of a doubling of CO2. In other words, if a doubling of CO2 in the atmosphere would increase the global temperature by 10 degree C., than climate sensitivity is 10 C.

However, there is no agreement on climate sensitivity. Even among supporters of the anthropogenic global warming theory the actual estimates vary widely. Even computer simulations vary from climate sensitivity of 2 C. all the way up to at least 6 C.

That is a huge difference. But all computer scenarios assume positive feedback. They assume that other climate factors enhance the warming effect of CO2 rather than mitigate it. Other researchers who have attempted to measure climate sensitivity have found negative feedback and produce low estimates of less than a degree C.

Obviously, we are dealing here on the level of a hypothesis, not a theory. There are a great many other related issues about which our knowledge is just too incomplete. And that doesn't even address the larger question of whether or not temperature is the major driver of earth's climate. There are many climate scientists who will insist that it is not.