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First of all, there's a variety of responses which have come from the left and it's a mistake to think that all the Greenies wish to employ the same means. The Liberals are the ones who have largely been pushing for increased regulation, it's something they pushed for before the advent of Global Warming and it's something they'll push for afterwards.
The State Socialists have declared this as irrefutable evidence of the failure of capitalism to concieve of reality beyond capital profit and the need for a huge push for state interventionism and control of the market to bring about a more human friendly system. They argue that progess is too slow and ineffective with the current system and we'll be screwed if we don't give ourselves over to a central authority.
The Libertarian Socialists, whom I might add make up a surprising bulk of student, grassroot and small-scale "greenie" groups, have declared that the only solution is a radical rethinking of how we utilise and transport energy and see this as an impetuous to push for more localised agriculture and energy production, as well as a decentralisation of renewable technologies and a push for greater independence.
So in actuality the leftist response to the crisis is varied and unsolidified, not driven as some may claim by some all powerful homogenising conspiracy.