You’re proving my point. 

Clearly that cannot be true. There is no proof that “intelligent beings” exist.
They aren’t on earth. That’s for sure.

“I’d expect credit card transactions (which occur in a much higher volume) to consume more power”
The power consumption per transaction could be higher for Bitcoin.

The cleanest energy source exists. It’s nuclear energy.
There is literally, at this point in time, NO cleaner alternative.
There is none. Solar power is promising unfortunately it isn’t cleaner.
It’s literally worse. every method is worse.