Calif. Governor Arnold Schwarzenegger is one of the heaviest-hitting environmentally conscious politicians anywhere. His state has taken unprecedented steps against global warming during his tenure, from a greenhouse gas cap-and-trade system to demanding utilities produce more power from renewable sources. And he’s at it again, this time hosting the Governors’ Global Climate Summit.

It certainly sounds impressive, especially when he calls it a “historic Summit” with a capital ‘S’ like that. But then you read in the Los Angeles Times about the cynics calling it nothing more than a grandiose gabfest and about how, of 49 U.S. governors, 31 Mexican governors and 10 Canadian premiers invited, only 6 are attending, and you wonder if it’s just a hollow green rep-building exercise.

But then, Obama comes along to give it the legitimacy it needs. In a videotaped message (above), Obama explicitly thanks those governors involved and pledges to reduce U.S. greenhouse emissions by at least 80% by 2050.

So today’s wrap press conference, with attendees pledging actions to “advance a global agreement in Copenhagen in 2009” (Copenhagen will host the U.N. talks on the next big global climate change agreement) is bound to get bigger coverage than it would’ve pre-Obama appearance.

See – he’s already making an impact.