Detroit — Green John McCain’s political pander for a summer gas-tax holiday betrays how shallow his commitment to fighting climate change really is – as well as how low a priority the public assigns global warming. Which is precisely why Washington is regulating greenhouse gases through the industry backdoor.

Step through that back door, however, and one gets a sense of the headaches government is causing right now (not to mention the considerable power Greens have over the U.S. economy). This week, Detroit is host to the 2008 Society of Automotive Engineer’s International World Congress — the largest convention of auto engineers in the world — and it is being roiled by Washington’s climate politics.

This year’s convention – titled “A Climate for Change” — is dominated by the federal government’s draconian edict mandating that the auto fleet achieve a fuel economy increase of 40 percent by 2020, regardless of what consumers want. Twelve years is not very long in an industry that works on 4-6 year product cycles requiring billions in investment.

The assembled executives and engineers are notably resentful that politicians have burdened their industry – rather than consumers via behavior-altering taxes — with the costs of Washington political fashion.

At a Wednesday morning session entitled “Will fuel economy sell?” panelist Scott Bailey of auto-supplier Delphi notes that fuel economy is not a top consumer priority. But, he says, the answer is no longer optional thanks to Washington. “We have to make it sell,” he says. Ford’s Robert Lee pointed out that Europe has only affected fuel economy with massive fuel taxation (gas prices hit $10-a-gallon in England last week) and favorable tax treatment for vehicles with low CO2 emissions. Both men expressed the perverse hope that gas prices would continue to climb, so that consumers’ needs would dovetail with the products mandated by DC pols.

Washington’s diktat, said Bailey, will require “unprecedented levels of innovation if we are to hit the targets.”

General Motors’ Vice Chairman Bob Lutz is more blunt: “Nobody knows how to get to 35 mpg (Washington’s arbitrary target) with a portfolio of vehicles roughly equivalent to today’s without loading in $6,000 to $8,000 of hybrid systems. We are not sure we can ‘save’ large vehicles.”

Contrary to know-it-all pols who think they have legislated the end of the internal-combustion engine, all the panelists agreed that advances, as Ford’s Andreas Schamel put it, “will come from gasoline, because that’s where the economies of scale are, that’s where market acceptance is.”