CO2 does not “trap heat” in the atmosphere and the increase in CO2 is not a buildup of our emissions. In fact these are two pseudoscientific myths that appear frequently in alarmist press reports and teaching materials. Neither one is true.
The science is quite different. It is actually pretty complex, which is why the climate change science is so widely debated.
No heat is trapped by CO2 in the air
CO2 both adds heat to the atmosphere and removes it, so it certainly does not trap it there. CO2 is a secondary greenhouse gas (GHG), with water vapor being the primary GHG. What being a GHG means is two different things, as GHGs both add and remove heat in the atmosphere.
It all begins when the sun’s incoming energy heats the surface of the Earth. Some of that energy is then given off as infrared light, which is usually called “long wave radiation” or LWR. A lot of this LWR simply passes through the atmosphere and goes out into space, where it is gone forever. But some of it is intercepted and absorbed by GHG molecules.
These energized molecules then give off this absorbed LWR energy to the rest of the air as heat. (Heat is not a substance; rather it is just molecular motion.) So at this point we can say that the CO2 has heated the air and this is as far as the alarmists go. What they do not mention is that when this heat energizes other GHG molecules, they give off LWR, thereby removing the heat.
So the energy comes into the air as LWR and becomes heat, then it goes out again as LWR, and is gone. No heat is trapped in this process. There is always some heat in the air as this process goes on, but it is like people coming into a store, then standing in line waiting to be served, then leaving. No one is trapped.
Once we see that no heat is trapped, we can ask whether adding CO2 necessarily increases the amount of heat (and the temperature) in the air. Thanks to the complexity of the climate system, the answer turns out to be not necessarily. Moreover, satellite observations tell us that there has been no CO2 warming since records began about 40 years ago.
The CO2 buildup is not made up of our CO2 emissions
It is pretty well established that the amount of CO2 in the air is increasing. It is usually said that this is because we are dumping a lot of CO2 into the air and a lot of it is staying there, building up year after year. This is more or less the standard concept of pollution, which the alarmists constantly invoke, but that is nothing like what is happening with the CO2 increase.
What the alarmists consistently fail to mention is that our emissions of CO2 are tiny compared to those that occur naturally. In fact natural processes both emit and absorb something like 25 times what we emit (the actual amount is not measured). This vast natural flow of CO2 into and out of the air is called the “carbon flux.” It is part of the carbon cycle that sustains all life on Earth.
The point here is that given this huge carbon flux, pretty much any CO2 that we emit is gone in just a few years. Something like 25% of the CO2 in the air is absorbed every year by natural processes, including the CO2 that we put there.
What this means is that the CO2 increase in the air is not made up of our CO2 building up. Our CO2 may or may not be causing the increase, someway or another, but it does not make up the increase. Let me say this again simply, the CO2 increase is not our CO2.
In sum, when you see articles complaining about heat trapping CO2 pollution filling the air, none of it is true. The increase in CO2 is not a buildup of human emissions and it is not causing the atmosphere to heat up.