August, 2005 — Hurricane Katrina blows into the Gulf of Mexico and blasts New Orleans to smithereens. Environmentalists quickly blame the storm on global warming — or at the very least, claim that warming will inevitably lead to more Katrina-like hurricanes. Although there is no clear scientific consensus on what impact a warming world might have on the frequency of big Gulf hurricanes, it’s enough to move public opinion significantly on the question of whether federal, state, and local governments ought to do something about climate change.

May, 2006 — Al Gore’s An Inconvenient Truth opens in New York and Los Angeles. The companion book becomes the #1 paperback non-fiction book on the New York Times bestseller list in July. The movie goes on to become the fourth highest grossing documentary in U.S. history and wins an Academy Award.

July, 2007 — Live Earth concerts to save the planet feature 150 top musical acts in 11 cities around the world. While it’s unclear how many people actually watched those concerts, Live Earth set a record for on-line entertainment with over 15 million video streams during the live concerts alone.

October, 2007 — Al Gore and the Intergovernmental Panel on Climate Change win the Nobel Peace Prize.

March, 2008 — The Heartland Institute sponsors a conference in New York City to showcase scientific skepticism about the seriousness of climate change. The event is received with uncharacteristically loud derision by the mainstream media.

Now, with all of that in mind, wouldn’t you think that the public would be growing more — not less — worried about climate change? You might, but you would be wrong. According to today’s Energy & Environment Daily (subscription required), a new poll conducted by Princeton Survey Research Associates and released by the John Brademas Center for the Study of Congress at New York University finds that Americans are less worried about climate change than they were a couple of years ago.

E&E Daily reports that the survey’s margin of error was +/- 3 percent. Here are the highlights:

The percentage of Americans who said global warming requires immediate attention declined from 77 in 2006 to 69 percent today.

The percentage of Americans who said they were “very worried” about global warming increased from 31 percent in 2006 to 39 percent in 2008. But that’s misleading; everyone gets “more worried” about everything in a presidential election year. What’s striking to me is that the rise in the number of those “very worried” about global warming was less than the rise in the number of those “very worried” about the four other issues surveyed by Brademas Center (Medicare, Social Security, and energy).

The declining number of those who said they were “somewhat worried” about global warming more than offset the increase of those who reported being “very worried.”

There are several possible explanations for this data. My guess is that it’s a little of each of the following.

Explanation #1 – The public has only limited patience for “end of the world” prognostications. If the world isn’t visibly ending from whatever boogey man is said to menace said world, most of us begin to lose interest. We’re all well aware that Earth has been sentenced to doom hundreds of times over by activists of various stripes but has somehow gained a reprieve time and time again.

Explanation #2 – The time horizon of most voters is very, very short. Getting people to voluntarily sacrifice for “the grandkids” or whomever is a near-impossible task. It would probably take a Katrina-a-year … and even then, that might not be enough. The mathematical certainty regarding the economic train wreck about to be visited upon “the grandkids” as a consequence of the trillions of dollars of unfunded liabilities for present federal health care and retirement programs does not engender sacrifice. It engenders shrugs and accelerated wealth transfers from the future to the present.

Explanation #3 – Global warming, if it plays out as the IPCC suspects, will be a slow-moving event. Panic over climate change has to compete with panic over Islamic terrorism, panic over housing markets, panic over globalization, panic over energy prices, panic over immigration, and episodic panic over dozens of other (usually dubious) worries. Simply put, global warming has a hard time competing with all of the other items on the policy agenda.

So conservatives, take heart. Enviros, take a valium.