Fact 1 - The greenhouse effect is real. If you don't believe it, visit a greenhouse and ask yourself why it is so hot in there compared to outside.
Fact 2 - CO2 is a greenhouse gas, meaning its presence causes the greenhouse effect. (proven many time with a simple high school experiment)
Fact 3 - Humans generate CO2 gases with their activity
Fact 4 - CO2 levels have vastly exceeded "normal levels" since mankind started burning coal and other things. (see the CO2 level history below from tiny air bubbles trapped in ice in Antarctica over the past 800,000 years) The graph shows that CO2 levels before coal never exceeded about 280 ppm (parts per million), and today it is above 410 ppm.
Source for this graph is the Department of Energy.
http://cdiac.ess-dive.lbl.gov/images/ai ... orical.jpg
People, we have established that mankind is creating CO2, and is adding to the greenhouse effect of the planet, now we are just arguing over how much it is effecting things.
I would also point out, if our energy sources started out 100% clean, and I came along and petitioned the countries of this planet to dump 40 billion tons of CO2 into the air, and would they be OK with it? I am pretty sure I know what the answer would be.
*NOTE:
Source: https://en.wikipedia.org/wiki/Ice_coreAn ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper, and an ice core contains ice formed over a range of years. Cores are drilled with hand augers (for shallow holes) or powered drills; they can reach depths of over two miles (3.2 km), and contain ice up to 800,000 years old.