Whom would you nominate to an international committee to save the planet?

St Bono, of Dublin.

He can bring a sense of cool to any occasion, can preach on any subject and would be happy to sing to the rest of them during teabreaks.

Mel Brooks. If there is anyone expert at controlling emissions, it would be him. Just look at Blazing Saddles for proof.

That's at least as sensible as George Harrison's role as point person for the Bangladesh relief efforts of the early 1970's which were ultimately quite successful.

Malala Yousafzai (Pakistani girl attacked by the Taliban) and a bunch of other nobel peace price winners.
Pope Francis and Archbishop Desmond Tutu
A few smart Muslim leaders too (none comes to mind)
Gideon Levy
Michael Moore
Jimmy Carter (or Bill Clinton)
Amartya Sen
Angela Merkel
Dany Cohn-Bendit
Lula
...

The only difference being that the late, great George was never up his own arse in any way.
Spiritual, yes.....hippie dippy, maybe....but a totally sincere and gentle human being.