All these extrapolation attempts need to be taken with a grain of salt.
One thing we know:
* carbon and methane that we release en masse in the atmosphere causes the temperature to rise globally, it has been known for decades. It has a negative impact on the stability of climate and thus food/safety.
Things we don't know:
* exactly how big is the impact of temperature on the habitibility of earth.
* how many degrees of increase is needed to be a danger to mankind's existence? Or how many people (even give or take) will suffer or die?
* how fast will science find applicable solutions and what speed is necessary to keep the harmful effects limited?
So we can keep on repeating that we are not doing enough to mitigate, or even that it is already too late, but that speculating does not solve anything.
Bottom line, we should keep trying to keep temperature increase as low as possible, on multiple fronts: more efficient usage of resources, less inequality between poor and rich, investing in technology, persuade people not to waste resources, thinking about alternative types of economies,...
Only future will tell if it were enough.