This paper discusses the concept: https://www.pnas.org/content/103/46/17184 https://www.pnas.org/content/103/46/17184 I think they were targetting "stop warmin

This paper discusses the concept: https://www.pnas.org/content/103/46/17184 https://www.pnas.org/content/103/46/17184 I think they were targetting "stop warming" more than "1990 levels", but they estimated 20 million tons/a few million square kilometers.