Actually there are four things up for debate.
1) How serious is the change in climate that is occurring and has it leveled off? And have the books been cooked by some in the scientific community, the hockey stick for instance is a complete fraud?
2) Are humans actually contributing to climate change?
3) If so, how much, what percentage?
4) Do humans have the capacity to reverse it?
There has been plenty of other climate changes within history. In the early 1600s we went thru a mini-ice age. In the 1300s we went thru a warming period that in parts of the world were we kept records was warmer than the current period. Humans somehow survived thru those period. I do believe we in the West need to have a smaller Carbon footprint, not because I'm convinced CO2 emissions are changing the climate as much as we simply can't afford all of the stuff we believe we need.