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In a recent blog post, Tufts University professor and former ExxonMobil executive Bruce Everett claims to have had hundreds of conversations with advocates of active climate protection over the last ten years. From these conversations he claims that they – an almost entirely unnamed group of “Climatistas”  –  make ever-changing, unsubstantiated arguments, and cannot answer his objections.

I’m not sure who his “Climatistas” are, or why they were struck dumb by his garden-variety climate-skeptic arguments. But here’s a quick response. I’ll try to resist the temptation to respond to his rhetoric in kind.

Substantively, there are eight paragraphs in his “Climate Change Switcheroo” commentary that argue against the “Climatistas.” Here are his eight main points, with my responses.

1.“We can’t tell yet if the observed warming is outside the natural range of variation.”

Year after year, we’re breaking records for high temperatures. The European heat wave of 2003, which killed tens of thousands of people, was outside the range of recorded temperatures. The wildfires that swept through Russia last year, devastating crop yields, were likewise outside the range of historical experience. I can put you in touch with my relatives in Texas, if you’d like first-hand information about this year’s “observed warming.” On the other hand, which parts of the world are getting colder? Has anyone broken any records for cold temperatures lately?

See Barnett et al., “Human-Induced Changes in the Hydrology of the Western United States” (Science, Feb. 22, 2008), a study that identifies human influences on declining snowpack, rising winter temperatures, and seasonal changes in runoff. See Westerling et al., “Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity” (Science, Aug. 18, 2006), on the alarming recent increase in the same region’s forest fires, closely correlated with rising temperatures.

2. The “embarrassing Climategate email scandal” has reduced the popularity of the “hockey stick” argument [a graph of temperatures vs. time looks like a hockey stick on its side, horizontal until recently, then angled ominously upward].

The “Climategate” scandal of 2009, in which someone stole and published a lot of e-mails from scientific researchers, established beyond a doubt that leading climate scientists are rude and competitive in private conversation. Shocking news, I know, but that’s about it. Repeated government inquiries in the U.K. and here have established that the stolen e-mails do not challenge or undermine the published record of climate science. Where is the peer-reviewed research showing that the “hockey stick” graph of temperatures is wrong? As I said, it’s getting hotter – just like the hockey stick graph implies.

3. The heat-trapping properties of atmospheric carbon alone would not account for the projected degree of warming; the “scary scenarios” are all based on “highly uncertain assumptions about non-carbon factors, such as cloud formation. Climate models tend to assume that all non-carbon factors enhance rather than mitigate the greenhouse effect… the point is at least arguable.”

It’s true that uncertain feedback effects determine the exact strength of global warming, and hence the temperature increase expected from any given level of emissions. The uncertainty, however, is asymmetric: it is easier to rule out the very low temperature increases that Bruce suggests as hopeful possibilities; it is unfortunately difficult, perhaps intrinsically impossible, to rule out dangerously high temperature increases. See Roe and Baker, “Why is Climate Sensitivity So Unpredictable?” (Science, Oct. 26, 2007), for a good summary of the current understanding of this complex issue.

It is simply not true that climate models assume all non-carbon factors enhance the greenhouse effect. IPCC calculations and all other major models include positive and negative contributions to global warming from a variety of gases and aerosols, with cooling effects from sulfates and some particulates. The interplay between positive and negative effects is central to these models.

4. “There are large numbers of scientists who disagree with at least part of the [hypothesis that warming is caused by human activity].”

Really? Is there a reason why they never show up on statistical surveys of scientific opinion? (Perhaps all five of them are too busy appearing on Fox News.)

A survey of 486 U.S. climate scientists in 2005 found 88% agreed or strongly agreed we have “great certainty” that human activities are accelerating global warming (Rosenberg et al., “Climate Change: A Profile of US Climate Scientists’ Perspectives,” Climatic Change, 2010). A survey of more than 3,000 earth scientists around the world found 82% agreed that human activity has been a significant factor in changing mean global temperatures; agreement was much higher than 82% among climate scientists, while lower among petroleum geologists (Doran and Zimmerman, “Examining the Scientific Consensus on Climate Change,” Eos, 2009). Another study found that 97-98% of the most active climate researchers agree with the IPCC conclusion that human activity is unequivocally responsible for global warming; the relative expertise, prominence, and frequency of publication was substantially higher for those who agree than for those who are unconvinced by the IPCC findings (Anderegg et al., “Expert Credibility in Climate Change”, PNAS, June 21, 2010).

5. “Some risks just can’t be mitigated at acceptable cost. The costs of decarbonizing the economy would be so high that it would require government coercion on a scale unprecedented outside of totalitarian countries.”

So why has Denmark moved so heavily into wind power? Are they secretly a coercive, totalitarian country? Or Germany, where elected governments from all major parties have continued to promote renewable energy (without destroying Germany’s remarkable competitiveness in world markets, by the way)? Why did the Stern Review and many other economic analyses conclude that 1-3% of world output – a smaller percentage than the US, or China, now spends on the military – would be enough to solve the problem? Does your understanding of democracy allow spending of that magnitude on the military, but not on the environment?

6. Studies that show carbon reductions are affordable, such as the McKinsey abatement cost studies, use unreasonable assumptions about capital cost.

Interest rates have dropped sharply in the last few years, as the economic crisis has unfolded, lowering the cost of capital. Meanwhile, the McKinsey studies, done a few years ago, also assume that oil costs $60 per barrel. As oil prices go up, the net cost of abatement goes down: the capital cost is unchanged, but the value of the energy saved is increased. Should we plan on oil returning to $60 per barrel any time soon? Or should we recognize that abatement is a useful hedge against high and increasing energy prices – just in case there’s another energy crisis in our future?

7. Some of the inarticulate Climatistas who Bruce has crossed paths with did not understand net present value, and believed that individuals should not discount future income.

Okay, if you found a student or two who didn’t understand or believe in net present value calculations, they were wrong. But try picking on someone your own size: does Nicholas Stern understand net present value, in the Stern Review? How about Martin Weitzman, a Harvard economist who’s no slouch at mathematics? Both of them believe that it’s urgent to do something big, and soon, about climate change. Serious economic models, which often find it’s possible to abate emissions, are done by analysts of clear economic literacy, employing net present value calculations. It’s not as easy and entertaining to mock them – but it’s a more important discussion to engage in.

8. Julie Nelson, the only named “Climatista” in Bruce’s commentary, allegedly believes that “humans would be much better off if we responded to threats viscerally and instinctively rather than wasting too much time analyzing pros and cons.”

Bruce urges readers to look at Nelson’s article – and you should. It is actually a thoughtful discussion of how economic theories and models often fail to reflect real-life experience; you’d never recognize it from Bruce’s snippy dismissal. Nelson’s conclusion is an excellent note to end on:

“The world we live in is profoundly unsafe, interdependent, and uncertain. Economics that neglects these facts—or, even worse, distracts us from them with stories about mechanism and predictability—does harm. It is high time for economics to catch up both with science, and with social needs, and become a positive force in dealing with climate change.”