Rolling Stone (ahem) includes Alex Epstein, author of The Moral Case for Fossil Fuels, on its list of top “global warming deniers.”  Epstein:

[T]hose who dispute catastrophic global warming are accused of denying the greenhouse effect and global warming. I experienced this in 2013 when I woke up to find myself named to Rolling Stone’s Top 10 list of “Global Warming’s Denier Elite” –in which they cited three articles of mine, each of which explained that CO2 has a warming effect!

How can anyone believe in anthropogenic global warming yet continue to enthuse over fossil fuels?  It’s a question of magnitudes, of course.  Massive warming is deadly; modest warming is fine.  Epstein thinks the magnitude of warming has been – and will remain – modest.  Which brings us to the obvious question: Why should anyone go with his judgment, rather than the scientific consensus?

There was a time, Epstein admits, that he didn’t take this challenge seriously. 

But there was so much going on in discussions of global warming , I didn’t know how to decide where the evidence lay. I would hear different sides say different things about sea levels, polar bears, wildfires, droughts, hurricanes, temperature increases, what was and wasn’t caused by global warming, and on and on.

With such a mess to work with, I – like most, I think – tended to side with the scientists or commentators whose conclusions were more congenial to me. I will admit to reiterating the arguments of skeptics of of catastrophic global warming with the lack of rigor I think is extremely common among believers. But I didn’t do this for long. I acknowledged that I didn’t really know what to think, and the idea that we might be making the Earth fundamentally uninhabitable scared me.

Most us, myself included, are in the same epistemic boat.  I’m not qualified to evaluate Epstein’s main claims about the magnitude of global warming.  But he expresses his main claims so clearly that experts shouldn’t find it hard to confirm or deny them.  Two claims in particular stand out.

Claim #1: While hard experimental evidence confirms a greenhouse effect, this effect is logarithmic; increasing CO2 warms at a decreasing rate:

While I’ve met thousands of students who think the greenhouse effect of CO2 is a mortal threat, I can’t think of ten who could tell me what kind of effect it is. Even “experts” often don’t know, particularly those of us who focus on the human-impact side of things. One internationally renowned scholar I spoke to recently was telling me about how disastrous the greenhouse effect was , and I asked her what kind of function it was. She didn’t know. What I told her didn’t give her pause, but I think it should have.

As the following illustration shows, the greenhouse effect of CO2 is an extreme diminishing effect–a logarithmically decreasing effect. This is how the function looks when measured in a laboratory.

Figure 4.1: The Decelerating, Logarithmic Greenhouse Effect


Claim #2: Complex interactions between this logarithmic greenhouse effect and other factors could generate a lot more warming, but this is not based on hard experimental evidence.  The only way to judge these more complex climate models is against observational data.  What we’ve learned over the past few decades is that these models systematically overstate warming:

Here’s the summary of what has actually happened– a summary that nearly every climate scientist would have to agree with. Since the industrial revolution, we’ve increased CO2 in the atmosphere from .03 percent to .04 percent, and temperatures have gone up less than a degree Celsius, a rate of increase that has occurred at many points in history. Few deny that during the last fifteen-plus years, the time of record and accelerating emissions, there has been little to no warming– and the models failed to predict that. By contrast, if one assumed that CO2 in the atmosphere had no major positive feedbacks, and just warmed the atmosphere in accordance with the greenhouse effect, this mild warming is pretty much what one would get.

Thus every prediction of drastic future consequences is based on speculative models that have failed to predict the climate trend so far and that speculate a radically different trend than what has actually happened in the last thirty to eighty years of emitting substantial amounts of CO2.

Which brings us to the single most striking figure in the whole book.

Figure 4.3: Climate Prediction Models That Can’t Predict Climate


[larger version]

My question for experts: Is there anything seriously wrong with this figure?  In particular, is it really true that virtually every major climate model overpredicts global temperature?  I’m genuinely curious, but I insist on a straight answer.