Charles Beddington, a dealer and scholar who co-curated the National Gallery exhibition, explains that he had thought of including the artist in this show, but then changed his mind.
If little is done in the coming years, Beddington says the "perfect storm" of threats will increase the likelihood of unrest, conflict and mass migration in various parts of the world.
Professor Beddington says now that oil prices have dropped again, domestic and international pressure to deal with energy issues that we will have to confront in the future may well decline.