|Courtesy: The Guardian|
In a way it’s an obscene question: if the planet warms by 4 degrees Celsius (°C), would only a billion
people survive and many billions perish? Obscene in the sense of the obscenity of arguing about the exact body count from a genocide. In the end it’s about the immorality, the crime, the responsibility, not the precise numbers.
But it’s a relevant question, in that Earth is heading towards 4°C of warming, based on emission reduction commitments so far. The Paris commitments are a path of warming of around 3.3°C, but that does not include some carbon cycle feedbacks that have already become active (e.g. permafrost, Amazon, other declines in carbon store efficiency) which would push that warming towards 5°C. So saying we are presently on a 4°C path is about right.