In terms of cost to government, again, it depends on how much we do domestically. If we have reasonably aggressive policies to reduce emissions domestically, then we'd probably have to buy somewhere in the order of 100 megatonnes a year internationally, which, depending on where these credits come from, could be somewhere between $1 billion a year to possibly as much as $2 billion a year.
On February 15th, 2007. See this statement in context.