I think this is a wrong measure for something that is happening constantly. We can calculate excess deaths from Covid because we have base (a year before the pandemic), but we can't calculate excess deaths from fossil fuels because we don't have anything to relate to, anything changing.

Every person needs to die and so in a steady state world it does not matter whether we are using fossil fuels or not -- the number of deaths every year will be the same (ie. the same as births). So you can't really say there are any excess deaths because there is no excess we can measure.

What would be more useful is a measure of how much it impacts average lifespan and healthy years (ie. how many years you can expect to live in relatively good health).