There is a debate, it's just not on the questions you're looking at.
Climate Change is by no means a 'settled' science, one of the most important questions scientists must answer is what the Climate Sensitivity is to CO2. There's a wide range of answers to this question by scientists, depending on which climate model you use, as well as many other factors.
The only debate is over the degree of how bad CO2 is, but we know it is 'bad enough' to be avoided. Whether it's really bad or just bad, we should move on to alternatives without that problem. As someone else said below, this is roughly like asking if there will be millions of climate refugees or billions?
Whether we are looking at 1.5C vs 8C is absolutely enormous in terms of what policies we should be looking to enact. Everything in this discussion is shrouded in a cloud of uncertainty due to the complexity of weather, and the thousands of negative and positive feedback loops which can take thousands of years to stabilize.
Popular science articles misrepresent the science and ignore the variance/complexity, in the end hurting the cause in the eyes of those who don't agree with the prescribed policies to address it.
Climate Change is by no means a 'settled' science, one of the most important questions scientists must answer is what the Climate Sensitivity is to CO2. There's a wide range of answers to this question by scientists, depending on which climate model you use, as well as many other factors.
http://imgur.com/a/vbOM0