The NFT here seems to be a publicity stunt to both raise money directly from the auction and also to raise awareness about the charity. I had never heard of this charity before this stunt, and I probably would not have heard of them without it. It certainly seems plausible that "using an NFT" here is a net good, even if there is some carbon cost.

You could argue against the stunt, but it requires more work that just stating "carbon costs." You'd have to check whether valueOfSavedLife * moneyRaised / 1235 + carbonCost < 0. And it looks like the auction is structured so that moneyRaised will be at least 2.5M, so the carbonCost would need to be pretty negative to make the sum negative. What is carbonCost?