Here's what it comes down to, carbon sequestered in the atmosphere since the start of the industrial revolution has increased significantly. In simple models and experiments carbon traps heat. Global average temperatures have raised a few degrees at a rate that correlates with the increase in carbon in the atmosphere. So, correlation: yes. Cause and effect: some say yes, some say no.
What do you do with this knowledge? Well, you could look at it like this example: "Well we could be poisoning our water. Do we continue our actions and take the risk or change and ensure that we don't poison ourselves." One would think you wouldn't want to take the risk, but lets say that isn't enough for you.
Here is some other intensives for changing our current energy paradigm.
Energy Security: we rely heavily on foreign oil and other fuels, most of which comes from the middle east, with oil prices controlled by OPEC. Even if we were to max out production here in the US and drill everything we have, we simply don't have enough supply. Next best option? Nuclear, hydro, solar, wind, energy efficiency standards, energy conservation.
Energy Value: Oil is getting damn expensive, and the price is only going north. Other energy options are seeing price decreases as the tech gets better. Need I say more?
Ocean Acidification: We know we are putting carbon in the atmosphere. The biggest carbon sink that pulls it back out of the atmosphere is the ocean (pretty simple chemistry). The problem with the carbon in the ocean is that it increases the acidity, which is hazardous to organisms that are important to our food supply and it damages corral reefs which are important for shore protection (harbors, shipping lanes, residential areas).
Technical stuff here