In his speech at the U.N. Summit on Climate Change today, President Barack Obama admonished world leaders that their nations “cannot allow the old divisions that have characterized the climate debate for so many years to block our progress.” Yet, during this week-long summit to lay the groundwork for the Climate Change Conference in Copenhagen in December, as world leaders take turns in making rousing speeches and proclamations, old divisions will continue to bog down any progress for carbon emissions reductions until President Obama and his fellow Summit participants make the final leap from certainty to action.

Enter Greg Craven, whose nationally acclaimed new book, What’s the Worst That Could Happen: A Rational Response to the Climate Change Debate (Perigree) shatters the back-and-forth raillery and unending road blocks over the climate change debate with a breakthrough rationale for making decisions.

In effect, Craven’s work completely derails the old divisions, and changes the question from “Who should I believe? to, What should I do? After all, the physical world is unaffected by our beliefs. It reacts only to our actions.”

Craven has developed a grid that “allows you to stop focusing on who’s right and instead ask, What’s the wisest thing to do, given the risks and consequences? Craven’s bottom line: Which mistake would you rather risk: the possible harm to the economy that skeptics embrace or the possible upheaval that activists warn us about? What is the more acceptable risk: the risk of taking action or not taking action?

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In the Age of Stupid (the climate change documentary screened around the world last night) , Craven is a wily and brilliant farm boy/physicist/teacher in the mold of Benjamin Franklin. His work has been hailed by critics as far-ranging as Middle East diplomat and military leader General Anthony Zinni, climate change pioneer author Bill McKibben, and bestselling “Storm World” author and science journalist Chris Mooney, who wrote: “Craven’s schtick is ‘don’t just trust me, think for yourself’. The truth, though, is that Craven really is an expert, just of a new breed that didn’t exist before the internet. In the climate debate, I would rather trust Craven than industrial lobbyists or environmental groups, and I doubt I am alone … I learned something from it — an achievement I might have thought impossible given my lengthy immersion in the climate debate … If Craven could get everybody who has weighed in on this debate to go through the exercises in the book, Al Gore should share his Nobel peace prize.”

In the spring of 2007, Craven became a YouTube sensation with his wildly creative and breakthrough video on climate change, “The Most Terrifying Video You’ll Ever See.” Over 7 million viewers later, Craven sat down and put his practical advice into his new book. Though he could not attend the U.N. Summit on Climate Change this week, Craven took time to answer a few questions about his work and ideas:

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Biggers: Your book seeks to guide us out of the “shouting match” over climate change. As hundreds of government and business leaders with varying views and ideas from around the world converge on New York City this week for a series of high-level meetings and events focused on climate change, how do observers construct their own “credibility spectrum,” as you suggest?

Craven: The main point is to unhook ourselves from the need for certainty before taking action. We do it in our daily lives — we fasten our seatbelt before we’re certain we’re going to have a collision — and military planners do it all the time. As one former U.S. Army chief of staff put it in a report on climate change, “Speaking as a soldier, we never have 100 percent certainty. If you wait until you have 100 percent certainty, something bad is going to happen on the battlefield.”

Constructing a credibility spectrum — by deciding ahead of time what factors influence the credibility of a source in your own eyes — helps you to avoid assigning credibility based on whether you like the statement or not (a universal human trait, I’m afraid, formally called “confirmation bias”). For instance, I base my spectrum on the source’s expertise, potential bias, track record, authority in the field, and reputation at stake, but yours may differ. Using a credibility spectrum to assemble and rank the totality of what you hear allows you to avoid letting one or two powerful statements hijack your risk assessment. Instead, you build up an overall picture, which helps make clear what seems like the best bet as to what (if anything) we should do about climate change, and how aggressively you think that path should be pursued.

Biggers: How could we apply your concept of the Magical Grid Machine to these high-level meetings?

Craven: It is so late in the game, and there are such time lags in the economic and climate systems involved, that we need huge policy changes right away. And policy makers respond to only two things: hordes of constituents, and lobbyists. Lobbyists are employed by businesses, which respond to hordes of consumers. So basically, the hordes have the ultimate power. Point the hordes in the right direction, and we can accomplish most anything.

In today’s wired world, our society is a non-linear complex system — email address books pointed to address books pointed to address books — which means it is capable of huge changes being triggered by tiny events. It is an avalanche poised on the slope. What the individual can do is start kicking pebbles down the slope trying to trigger the avalanche, by spreading the idea of risk management — of unhooking from the need for certainty and instead focusing on “given the risks and probabilities, what seems like the best bet for what to do?” For example, I’m just a Joe Schmo science teacher who posted a video on YouTube. And now over 7 million people have seen me drawing a grid on a whiteboard. Think of what can happen if we have a million people trying a million different things, trying to trigger the avalanche of public awareness and political will.

So the best way for you to apply the Magical Grid Machine to the high-level meetings is to spread the word, enlist the hordes, crash the meetings and give them the book, draw decisions grids on your bare chests and line the streets outside, do the silly and outrageous, the unexpected and unusual (but polite — polite counts a hell of a lot for the big shots, who have become accustomed to angry protests) to call attention to the idea of risk management, and let them know that the hordes demand it. When the stakes are the world, how can we possibly afford to make anything but the most conservative bet?

Biggers: The Age of Stupid film depicts a nightmarish future, looking back at our inaction over climate change. Do you think this is an effective way to trigger action and discussion, or another doom and gloom effort that will ultimately squash initiative? And discuss your view on how we need a new ethic beyond optimism or pessimism.

Craven: Such efforts are admirable and necessary, but they have only worked at the normal pace of social and political change. It is so late in the game, and we have dithered for so long, that we no longer have time to wait for that to happen. We need to change HOW social change happens. We need an epidemic spread of awareness and will. And epidemics spread by viruses, in this case a “meme”–or viral idea–that self-propagates. The grid in my “Most Terrifying Video You’ll Ever See” became a meme: I gave the video URL to just 100 students, and two years later, over 7.2 million people have watched it.

Both optimism and pessimism seem to represent a sort of throwing up of the hands, a surrendering to the whims of fate. “Things will be okay.” “We’re doomed. There’s no use even trying.” And that is absolutely not what we need right now. We need to realize that whether things work out okay or not depends on the effort we put in right now. Don’t get me wrong–optimism can be very useful at times. When the plane is going down and you’re in a passenger seat, optimism would be a great service to you. But if you are the pilot of the plane, it would be detrimental, because it would be calming, and you need to be at your sharpest. The pilot of a plane in trouble shouldn’t spare a thought for the calming idea “Things will be fine.” Concentration, skill, determination, awareness, and a keen understanding of the physics at hand are what will get you safely back on the ground. When the plane is going down, it is time for the best in you to come out. So that’s the mindset we need right now. When I think of it, and how it compares to the passivism of either “being an optimist” or “being a pessimist,” the image that invariably pops into my mind is that of Rosie the Riveter, from the WWII poster. That iconic image, of the individual citizen rolling up her sleeve to answer the call of duty, to do whatever is necessary to preserve the world she loves, will forever be burned in my mind. It is the embodiment of the mindset we need at this moment.

We don’t have a name for that attitude, so for lack of a better word, in the book I label it “Rosie-ism.” I believe our best hope is in asking each motivated person to focus their energy on passing on the meme to as many people as they can, and telling them to do the same. You reach ten, who each reach ten, etc., and in just 5 steps that’s over 100,000 people who have been reached. Because of YOU. That’s power. Use it.

Biggers: You invoke our extraordinary World War II mobilization and conclude: “..massive government action, when driven by the people, can accomplish the seemingly impossible in an amazingly short time. And it can do so without dooming the economy.” But how can a war-scale mobilization now, as you depict, not add to our carbon emissions crisis?

Craven: This time it’s not about a mobilization for building tanks and planes. It’s a mobilization of political will, of individual effort, of willingness to make collective action a top personal priority. On Dec. 6, 1941, we in the U.S. were focused on ourselves both personally and as a nation. But on Dec. 8, after the bombing of Pearl Harbor, everyone woke up with a different mindset. Instead of “What’s in it for me?” their first question became “What can I do?” Instead of “What’s it going to cost?” their reflexive response was now “How can I help?” I’m convinced that if we go through a similar transformation now, then we can tackle climate change easily, with a minimum of disruption and cost. But scientific societies, military planners, and now even the insurance industry all agree: the longer we wait, the more costly and disruptive the necessary changes will be.

Biggers: Anything else you want to add?

Craven: This part is key. The book is designed and packaged as a decision-making system to help the harried lay person make a decision about the climate change debate. Grist readers don’t need that, so why would they care about the book. Here’s why. Such fiery calls to action that I’m issuing here have not worked — and will not work — with the 80 percent of Americans who are too busy with life, and too overwhelmed by the shouting match to pay much attention to climate change. And make no mistake — that great unengaged majority is where the battle will either be won or lost. Soccer moms and NASCAR dads. Good people busy with life, and skeptical of calls of doomsday (we’ve heard them all our lives and hey — we’re still here, right?)

The ideas in the book are designed precisely to reach them. It is a can opener, a tool designed to break through, to puncture the membrane of doomsday fatigue that allows calls to action to roll right off the ponderous body politic like water off a duck. So this book is a brand-new, innovative tool for achieving the goals of your readers: to spark significant, widespread action to combat climate change by gaining access to the largest demographic out there: people who don’t see climate change as an urgent issue. The risk-management-for-the-layperson approach in my book may or may not work, but it has one thing going for it. It has the virtue of never having been tried. There is nothing else like it out there. Bill McKibben himself — the author of the very first popular-press book on global warming — wrote that my book “trumps most of our accounts of the global warming crisis … because the author has actually figured out what actions make sense. Changing your lightbulb will help a little, but changing the political debate will help enormously — and this book will get you started down that path.” So take this can opener, modify it as you see fit, and get to work on enlisting everyone else.