Bitcoin mining is really contributing in the global warming but as others are saying even banks are doing the same maybe when the time comes that bitcoin replaced the currency fiat system then it will be an acceptable use of energy and contribution to the global warming.
I think its very minimal or even neglectable to what really affects global.warming on a major scale. He focus should be in a more bigger scale and mining btc is the least among those.
Yeah it should be low respectively to the other projects using electricity. Bitcoin's production is not that huge and don't consume that much electricity. Think about giant oil production points, they consume tons of electricity.
Bitcoin is still environmental friendly.