A Swedish scientist explains the 33° C “Greenhouse Effect” as a result of gravity plus the specific heat of the atmosphere. Thus, if you want to change the net “Greenhouse Effect”, you need to change gravity (impossible) or the specific heat of the atmosphere (extremely difficult). (link)
The core of his argument is this: When you calculate the temperature of a certain piece of air, you need to consider the pressure of that piece of air. As you move up, the pressure decreases according to gravity, while the makeup of the air doesn’t really change much. (Modifying the content of a gas doesn’t change the specific heat of the gas all that much—all gasses are roughly similar to each other.)
The 33° C temperature difference between the air at the ground and the upper layer of the earth is thus accounted for.
In other words, there is no measurable “Greenhouse Effect”: All the temperature gradient is explained simply with gravity.
Folks, go ahead and fill the atmosphere with CO2. The plants love it, and it isn’t harmful, even at high concentrations. The very fact that CO2 is the by-product of the burning of natural gas and oil means that by doing so, we are actually helping people in poor parts of the world grow more crops and have more natural resources, such as wood and animals, to build up their economies with.
Other gasses that are a byproduct of burning fossil fuels are dangerous, but we have the technology to limit them.