why does jimmy call himself snowman after the plague?

Jimmy has given himself the name"Snowman" according to Crake's rule, which states that no one in the society of Crakers can have the name of someone or something else that currently exists. Globalwarming has made snow obsolete, so the children have no notion of what a snowmanis. Snowman is himself a remnant of another time in history, so it is fitting that he hasan anachronistic name that holds no meaning in the present. Also appropriate is themodifier "Abominable," since Snowman is presumably the only member of the humanspecies who has survived catastrophe.

http://www.scribd.com/doc/54576810/2/Section-1-pages-1−12