> So immediately not using Bitcoin would save as much CO2 as 4.5 million cars of the road

Which would have zero net effect on climate change (total number of cars in the world is 1.4 billion). Conversely, transition all cars to electric, renewable sources and dirty bitcoin emissions still won't be a problem (assuming they can be capped at some value instead of growing indefinitely).

In other words, current bitcoin contribution to climate change is the last of our problems- for now. But I understand that the idea of such an amazing amount of energy being wasted is something that immediately triggers an innate sense of abhorrence.