Knowledge is gained mainly through two mediums.
First is your own experience. You go and do something whether it be a chemistry experiment or enlist in the Army.
Second is you rely on someone's experience other than your own. This is where history makes its money. You can't obviously go and live the 18th Century, but you can sure read a whole damn lot about it.
With the exception of some of the "hard sciences" the bulk of "Edumacation" here in these United States is based on second hand experience. This is obviously the cheapest way to do it, but it is also the easiest way to indoctrinate a large quantity of youth with wrongheaded ideas.
Here are two things that I was taught in school based solely on secondhand knowledge.
The landfills are filling up.
The earth is warming and it is all the fault of SUV drivers.
In Fifth Grade I had to read about the "barge that no one wanted", the Mobro, which was used as anecdotal proof that landfills were dangerously overfull. Unfortunately nothing could be further from the truth, landfill capacity was actually increasing and has been since. Yes there are fewer overall landfills, but the ones now operating are larger and more efficient. Just like the meat packing industry, we went from thousands a few decades ago to a handful today.
So the "landfills are filling up" myth was easier to debunk than the "earth is warming because of SUVs" myth.
And it is a myth, because there are no well designed experiments that can show the mechanism of action proposed by the AGW crowd is in fact viable. As "greenhouse gasses" were explained to my Fifth Grade brain, "greenhouse gasses trap and reflect IR radiation back down to Earth instead of letting it escape into space." Which is a horrible mangling of an extreme over simplification. What "global warming" as proposed by those who subscribe to this theory, is that increasing CO2 content in the atmosphere will change the heat carrying capacity of the atmosphere to the point where it will get warmer, the same way that a thicker blanket on top of you in the winter will keep you warmer.
This has some problems. First is the "short wave in, long wave trapped" model hasn't been demonstrated. Imagine trying to boil a pot of water with a blowtorch, if you heat the bottom of the pot you can achieve a boil fairly quickly as the heat naturally wants to move upwards. Now imagine trying to boil that same pot of water with the same blowtorch, but instead from the top down. You have the same amount of energy going into the system, but you will have fantastically different results in terms of whether or not you can achieve a boil (the engineer in me says with a big enough torch most anything is possible).
Now the sun is the blowtorch, and the water is the atmosphere, and the pot is the surface of the earth. So how does the sun heat our atmosphere? This is a good question because understanding the mechanics is key. The atmosphere is largely transparent to solar radiation, but the surface of the planet is not. The surface is warmed by the solar radiation, and CONVECTION warms the air. Cool air drops and comes into contact with the surface where is warms and then rises to be replaced by cooler air. Changing the carbon dioxide content of the atmosphere does not change this cycle of convection cooling.
If CO2 were to absorb more long wave IR, then it would simply go higher into the atmosphere before releasing that energy. Which is why the AGW crowd is looking very hard at weather balloon data, because if the atmosphere is warming, it should be warming at high altitudes long before the surface data. But I hear about surface data all the time from AGW supporters. I bet you do too.
And to get back to the "I've read it vs. I've done it" go ahead and get a pot, blowtorch, and water and see for yourself if there is a difference. It is a gross oversimplification of the planetary system, but the principle is the same. And anyone who says "it's too complicated to explain" is full of BS.
And finally, I do believe the Earth is in a mild warming trend, but due solely to solar forcing.