Ignoring the debate over how much the CO2 impacts the temperature, which other comments address, there are likely a few things at play. First, "BigBusiness" has a vested interest in playing down any risk, so they sink considerable money into campaigning against climate change (political, media, etc). Second, people are conditioned to absorb quick soundbite factoids, not complex models, so "nuh-uh, fake science" hits home better than {complex model}. Plus, change is scary - either doomsday temperature increases OR give up cars and airplanes and cheap hamburgers? Yikes!