That figure is slightly misleading without context.

The billion deaths are total premature deaths. It's analogous to the total covid death toll. Have millions of people died due to covid? Yes. Were the deaths uniformly distributed across the world's population? No. The majority of premature covid deaths were concentrated in specific groups of people.

The climate change death toll is similar. People who are living in already precarious situations will be disproportionately impacted.

I think lots of people see that billion deaths number and imagine tornados, hurricanes, and heat waves destroying western cities. In reality, it will largely be the sick, young, and elderly in developing nations prematurely dying due to resource scarcity.

Obviously still a major problem, but the context is necessary to develop effective responses and solutions.