The first 24 minutes of Eric Posner and Heather Hulbert’s Bloggingheads discussion on Sunday was focused on global warming, and unintentionally revealed the political opportunity John McCain is squandering by supporting a cap-and-trade policy.

While Hulbert comes across as somewhat naïve by asserting that, for example, the US will increase its leverage with India and China by preemptively imposing emissions restrictions on ourselves (somebody needs to tell her the old story about free milk and a cow), and Posner comes across as somewhat tougher-minded, neither can articulate a reasonable argument to get 51% of American voters to support this. Posner makes the valid points that: (1) the costs of global warming will be grossly disproportionately borne by people who don’t live in the United States, (2) cap-and-trade is likely to be very expensive for the US, (3) achieving a necessary global agreement is essential and will be very difficult, and (4) such an agreement will require intrusive management and enforcement within national boundaries by some kind of supra-national authority. Other than that, it sounds like a real political winner. And this is a discussion between two liberals who pretty much agree on the subject.

The only way that aggressive emissions restrictions will become law in the US is if they have no significant political opposition. Unfortunately, this appears to be the approach of the McCain campaign. Of course, by accepting the premise that global warming is an emergency worth almost any cost to address and that the US should act preemptively, all McCain is doing in setting himself up to give at the office over and over.

Here is one of his top campaign advisers, Douglas Holtz-Eakin, in an interview yesterday with David Roberts of the environmental site Grist:

Question: The reports and research I’m familiar with say that cap-and-trade is a necessary but not sufficient step. I’m trying to get a sense of where McCain draws the line.

Douglas Holtz-Eakin: So would this rule out efficiency measures, with the evidence that people don’t buy the most lifecycle-energy-efficient appliances and as a result might need some help where pricing alone doesn’t do it? I don’t want to suggest he’s taken that off the table; of course he’d still be interested in that.

Great, cap-and-trade is just the beginning.

It gets better – if you read further in the interview, you learn that McCain is leaving wiggle room to put forward more aggressive emissions targets. Later, you get to see some pretty fancy footwork from Dr. Holtz-Eakin when he’s asked if cap-and-trade will “raise energy prices for average families and slow the growth of GDP”, and he tries to avoid saying ‘yes’ without actually saying ‘no’. (When an answer starts with “I am a Ph.D. economist”, you know it’s going to be good).

If you want a more realistic foretaste of what the economic and political effects of cap-and-trade would be, read the story in Sunday’s LA Times ( h/t Andrew Sullivan ) that opens with these two sentences:

Fighting global warming is the feel-good cause of the moment.

But in California, the self-congratulation that followed the 2006 passage of the nation’s first comprehensive law to curb emissions of planet-warming greenhouse gases is fast turning to acrimony.

In the article, Michael Peevey, president of the California Public Utilities Commission, says:

“There’s no free lunch. We have to reduce CO2 by 174 million tons by 2020. But no one wants to face up to the cost. Everyone wants everyone else to pay.”

Just so.