Everyone laughed at you because YOU ARE WRONG. I don't even need to talk about chemistry, a little basic knowledge of planetary science will do the trick.
The science behind man's impact on global warming is not that hard to understand. Let's take Venus as an example. There is good evidence that Venus was much like Earth, with bodies of water and plate tectonics, but it experienced a runaway greenhouse effect. Too much CO2 was being added to the atmosphere, causing the planet to warm up to the conditions we see today; we can't even land anything on the surface because inside the dense CO2 cloud the planet is just too hot. As the planet heated up, more liquid water became vapor, heating the planet more, vaporizing more water, etc. until the planet was what we see today. The far side of Venus is much hotter than the far side of Mercury, and the relative atmosphere densities is the reason for this.
Mars had basically the opposite effect, there wasn't enough CO2 production and not enough water vapor to maintain a good greenhouse. Eventually more water kept freezing, thus further cooling the planet, causing more water to freeze, etc.
Humans produce a large volume of CO2, a known greenhouse gas, and the production of CO2 does warm the planet. It doesn't matter whether or not we know how much warmth we are creating, but humans definitely warm the planet via carbon emissions. To deny that we have any impact is ignoring the facts. There's no way to know for sure how much hotter the planet is now than it would have been without our carbon emissions. It's impossible to know whether Earth is going through a natural cooling or natural warming phase right now because you generally can't measure these things on a day to day basis; the sample size is not large enough to come to any conclusions.