If global warming reaches or exceeds two degrees Celsius by 2100, University of Western Ontario's Joshua Pearce says it is likely that mainly richer humans will be responsible for the death of roughly one billion mainly poorer humans over the next century.
Afaikt the paper refernced in the article is The Human Cost of Anthropogenic Global Warming: Semi-Quantitative Prediction and the 1,000-Tonne Rule. .
From the abstract:
The key part of this being that it specifies 2C of warming. According to the climate action tracker, with current policies are on track for 2.7 degrees of warming by 2100. So assuming no further polices to move back to 2C or less, the 1 billion deaths could be larger.