After years of being accused of believing something I didn't believe—or, more accurately, not believing something I really did—I made headlines last month for changing my mind even though I hadn't.
Confused? Imagine how I feel.
It's worth explaining what happened to me because it tells us something important about why the global warming debate has produced so little in the way of results.
First, a little background. Ever since 2001, when I published "The Skeptical Environmentalist"—a book in which I argued that the world's environmental problems were getting better—I've been wrongly accused of being a global warming denier.
The fact that I've always asserted the reality of man-made climate change never seemed to make an impression on my critics. What mattered was that I had the temerity to question two key tenets of the received wisdom about global warming: I was skeptical of the idea that we were facing the apocalypse, and I didn't accept that the only solution was to mandate drastic cuts in carbon emissions.
That's the way it is with heresy—there is no middle ground. Either you believe global warming is the worst problem mankind has ever faced and that cutting carbon is the only solution, or you are an antiscientific ignoramus who probably thinks the Earth is flat.
My reputation among climate activists worsened in 2008, when the Copenhagen Consensus Center, the think tank I founded, published the results of a wide-ranging cost-benefit analysis of solutions to 10 of the world's most pressing problems. We assembled a group of top economists and asked them to assess which solutions to which problems would deliver the most bang for the buck. In addition to global warming, we considered issues like malnutrition, unsafe drinking water, malaria and terrorism.
The main global-warming solution our experts analyzed was the carbon-cutting approach advocated by Al Gore and endorsed at the 1997 global climate summit in Kyoto. We found that compared to solutions to other problems, direct carbon cuts were woefully ineffective. For example, while every dollar spent on fighting malnutrition would yield nearly $20 in benefits, every dollar spent on cutting carbon would avoid much less than a dollar of global warming damage. When we published our list of investments we thought should be prioritized, cutting carbon was near the bottom. Once again, I was pilloried for being a global warning denier.
The Kyoto approach is not the only way forward. In 2009, we convened another group to look at a variety of potential solutions to climate change beyond simply cutting carbon. Our experts (including three Nobel laureates) identified a number of other approaches to the problem that were economically feasible and likely to have a quicker and more powerful impact.
The most promising involved massive increases in R&D funding for green energy technologies and geo-engineering. I spent a good part of last year and most of this year advocating for this sensible approach to solving global warming, which is "one of the chief concerns facing the world today," as I said in an Aug. 31 interview with the Guardian, the British newspaper.
What happened next was startling. The Guardian reported my commonplace observation as evidence of "an apparent U-turn" by "the world's most high-profile climate change skeptic." This set off a media stampede; news organizations around the world scrambled to report my so-called change of heart.
I tried to explain that I had always considered climate change to be a problem. The only thing that had changed was that we finally had some good solutions to consider. Some people took the point, but just as many didn't. As far as the latter group was concerned, I had finally seen the light, and that was that.
I suppose I should take some comfort in the fact that I've been accused of being both a denier and a warmist. But the polarized nature of the global warming debate is no laughing matter. Limiting the debate to only two valid positions—for or against—makes a constructive discussion impossible. If we truly want to make progress on climate change, we must acknowledge a middle way—one that recognizes that while we do need to deal with the reality of global warming, solutions based on worst-case scenarios will actually do more harm than good.
The smart middle path means making green energy so cheap everyone wants it. There's nothing confusing about it.
Mr. Lomborg is director of the Copenhagen Consensus, a think tank, and author of "Cool It: The Skeptical Environmentalist's Guide to Global Warming" (Knopf, 2007).