Prediction by Extinction Rebellion’s Roger Hallam that climate change will kill 6 billion people by 2100 is unsupported – Climate Feedback
https://climatefeedback.org/...imate-change-will-kill-6-billion-people-unsupported-roger-hallam-bbc/

What science projects under plausible scenarios of human courses of action is varying degrees of further disruption of fundamental planetary life support systems (e.g. water, agriculture, ecosystems) needed to support the nearly 8 billion humans currently living on Earth. This disruption poses some degree of existential risk to civilization as we know it—with the amount of risk likely still depending on how rapidly we reduce radiative and ecological forcings—but these degrees of risk are not quantified with any certainty. Ice models have had difficulty projecting the melting rate of the Greenland ice sheet; predicting the mechanism of the collapse of civilization and the number of lives lost as a result is a far more complex problem, and there is no scientific consensus that six billion lives will be lost. On the other hand, models have tended to underestimate ice sheet melting, and model projections in general have been systematically “conservative.” I unfortunately don’t see how the possibility of six billion deaths can be ruled out with confidence, especially when the intrinsically unpredictable but real possibility of climate-related war (which could include nuclear weapons) is considered. In other words, Hallam’s claim is speculative, but given the depth and rapidity of anthropogenic change, so is confidently ruling it out.

While I don’t agree that “science predicts” the death of six billion people, in my opinion Hallam’s broader warning has qualitative merit and in the context of a lay translation of risk his use of “six billion” might reasonably be interpreted as figurative, an illustration of a worst-case scenario (again, that I don’t think can be ruled out). Whether to interpret this claim literally or figuratively is a question perhaps best left to humanists. Given this ambiguity I judge it “unrateable.”

Hyperwall: Earth: A System of Systems
https://svs.gsfc.nasa.gov/30701