It baffles me that some people actually believe that those concerned about global warming think that it will cause the end of humanity. It won't. Even if the most catastrophic predictions come true, not only will life on Earth continue on just fine, but human life will also continue. We are a very adaptive species and even in the case of extreme climate change, parts of the Earth will become more hospitable to humans than they are now. It just happens that people concerned about climate change don't think that 20% or more of the human population being wiped out is an acceptable path to take when reasonable alternatives exist.
It is possible for us to reduce CO2 emissions right now, with minimal economic impact, if we are willing. All it would take would be a concentrated push towards nuclear power generation, coupled with electric vehicles for transport and we could reduce emissions in short order without destroying any economies. Of course instead both Germany and Japan are dialing down their nuclear programs in favour of burning more coal.