In the Climate Casino: An Exchange

Roger W. Cohen, William Happer, and Richard Lindzen respond to William D. Nordhaus's piece Why the Global Warming Skeptics Are Wrong, in the NYRB:

In the March 22, 2012, issue of The New York Review, William Nordhaus presents his opinion on why global warming skeptics in general, and the sixteen scientists and engineers who wrote two Wall Street Journal Op Eds1 in particular, are “wrong.” We are three of those sixteen authors, and we respond here to Professor Nordhaus.

Professor Nordhaus’s essay contains six points.

The first point contorts the obvious fact that there has been no statistically significant warming for about the past fifteen years into a claim that we did not make: that there has been no warming over the past two centuries. Professor Nordhaus proceeds to confuse this with the issue of attribution, i.e., the determination of what caused the warming. Attribution is a distinctly different matter. While there is much to contest in the published temperature records, there is general acceptance that there has been a net increase in global mean temperature similar to that shown in Professor Nordhaus’s first graph.

The prior two- to three-hundred-year period was much cooler and is known as the Little Ice Age, and, of course, a longer record would have shown still-earlier periods as warm or warmer than the present. The observation that the last few years include some of the warmest years on record no more implies future warming than record stock market highs imply a steadily rising future market. The fact that warming has greatly slowed does imply that, at the least, there are other processes that are currently competitive with the impact of steadily increasing greenhouse gases.

William Nordhaus replies:

In reading the letter from Roger Cohen, William Happer, and Richard Lindzen (CHL), I have the sense of walking into a barroom brawl. They defend the article by sixteen scientists in The Wall Street Journal by firing a fusillade of complaints at everyone in sight, including Science editor Donald Kennedy, climate scientists with hacked e-mails, columnist Paul Krugman, biologist Paul Ehrlich, activist Robert Kennedy Jr., economist Nicholas Stern, and even former Vice President Al Gore.

However, when all the shooting has stopped and you look up from behind the table, what you see can be summarized in one central point. They argue that global warming is full of uncertainties, but its dangers are being systematically exaggerated by climate scientists. I will review the key issues in this response.