Sometimes I worry that I’ve run out of new things to blog about, but then out of the blue up pops something that proves me wrong. I recently received an email from Joanne Nova, who writes a blog where she claims global warming isn’t caused by human created greenhouse gas emissions. In her first email to me she wrote “there is no empirical evidence left that supports the theory that man made CO2 makes much difference to the climate.” Note, “no empirical evidence”, not “I disagree with the evidence”, or “there is contrary evidence” – but there is no evidence. None! She emailed me to ask why I had come to a different conclusion from her.

Why do I accept global warming science as being true? Well, it’s partly because I followed the many claims of the global warming “skeptics,” and although their arguments had been debunked numerous times by experts (for example, read RealClimate’s Responses to common contrarian arguments), the so-called skeptics kept repeating the already debunked arguments. After a while you just start thinking, “but that’s been explained already,” and stop taking those people seriously. So that would be my initial reason. But the other main reason would have been the thousands of articles published every year in peer reviewed scientific journals, virtually all of them supporting the anthropogenic global warming (AGW) hypothesis. And it’s also because of the denier tactics employed by the “skeptics”. (More on this later.) Nova writes back that this is argument from authority, and that it’s intellectually lazy to argue this way. Well, I disagree.

Argument From Authority

It isn’t necessarily fallacious to consider that thousands of climate scientists writing in peer reviewed journals might know more than you do about such a complex subject. Of course, this one is a little tricky for newbies, and I’m sure I got it wrong myself initially. Nizkor is one of the many sites that tries to explain it:

…a person who is a legitimate expert is more likely to be right than wrong when making considered claims within her area of expertise. In a sense, the claim is being accepted because it is reasonable to believe that the expert has tested the claim and found it to be reliable. So, if the expert has found it to be reliable, then it is reasonable to accept it as being true.

What we have here is trust in the scientific method. And we trust it because we have reason to believe it works – just look around you. (You’re reading this on a computer aren’t you?) And on a blog that promotes science and the scientific method, I’d have to be pretty perverse, or have a very good reason, to oppose thousands of peer reviewed scientific papers.

Note that what we should have is trust in science. This is not the same as faith, which is what Nova claimed I have. Faith is belief without evidence, while trust is acceptance of something based on what we have experienced before – ie what has worked and what has been right. In other words, trust of the scientific method is based on evidence that it works. Claiming that trust and faith are the same thing is the fallacy of equivocation that I have written about before. The fallacy is to use the same word in different meanings in an argument, implying that the word means the same each time. Implying that trust is the same as faith is actually the classic example I gave two years ago to explain the fallacy. Hilariously, Nova responded to this point with dictionary definitions of trust, that I think were supposed to show that trust can be defined in the same way as faith. But duh, that’s the point. They can be defined in the same way. But they can also be defined differently. And employing these ambiguous definitions s how they can be used to make a fallacious argument. Just because a dictionary gives definitions of the two words, and some of the definitions are similar, that doesn’t mean that trust in the scientific method is the same as faith. Nova even debunked her own point by writing “Planes don't fly on "trust". They fly on physics.” Yes. But I don’t need to understand the physics to get on a plane. I get on a plane because I trust that planes fly – and that trust is based on what we see in the real world (all those planes in the sky) not on faith.

Of course, trusting experts isn’t the same as Michael Egnor listing dead philosophers and scientists who he claims agreed with his views on Dualism. Science has moved on since the days of Galileo and Newton, and who knows what they might think now? It also isn’t the same as a certain commenter we all remember suggesting that since he studied plant breeding 30 years ago, his arguments on genetic engineering must be correct and everyone else’s wrong now. Those were fallacious appeals to authority because the people quoted were not necessarily experts. That would be the actual argument from authority fallacy.

It’s not intellectually lazy either to accept the majority peer reviewed science on a topic in which I’m not an expert. I don’t have any obligation to research and become an expert on every subject under the sun to determine whether to accept or reject a claim; I’ll study in detail only the subjects I feel an interest or a need to study, and no more. So sometimes I will rely on experts. Of course, relying on experts is weaker than understanding the evidence in detail, no one would deny that. And this would be a problem if I were writing a blog on global warming, or even writing posts on the details of global warming. But I’m not.

Nova replies that in that case, I shouldn’t refer to the AGW “Skeptics” as “deniers.” Again, I disagree. I refer to them as deniers because they also rely on denier tactics.

Denier Tactics

As I said, one reason I gave up with the global warming (so called) skeptics, was because of the denier tactics they clearly relied on. Here I think it would be useful to refer to Denialism Blog and their explanation of What is Denialism, because why reinvent the wheel? They talk about five general tactics used by denialists, namely:

Conspiracy Selectivity (cherry-picking) Fake experts Impossible expectations (also known as moving goalposts) General fallacies of logic.

I would add a sixth, namely continuing to repeat arguments long after they have been debunked. Climate denialists like Nova rely on many of these techniques, as I will show using this email exchange and her own web page.

Selectivity (Cherry Picking)

Denialism Blog explains Selectivity (Cherry Picking):

Denialists tend to cite single papers supporting their idea

Bingo. Nova claimed AGW had been “falsified” by David Evans’s The Missing Greenhouse Signature paper (which is not a peer reviewed paper as far as I can tell, despite what Nova claimed). This paper starts with:

Each possible cause of global warming has a different pattern of where in the planet the warming occurs first and the most. The signature of an increased greenhouse effect is a hotspot about 10 km up in the atmosphere over the tropics.

Read the second sentence in that piece again. It’s presented as a fact that, if falsified, falsifies the whole of AGW. The problem is, as far as I can tell, it’s not true. For example, Tim Lambert writes:

This couldn't be more wrong. Study the graphs below (from RealClimate). The left one shows the pattern predicted for doubling CO2, while the right one shows the pattern for a 2% increase in solar output. Both patterns include a hot spot. The difference between the two graphs is that the CO2 one shows cooling in the stratosphere, while the right one does not, so the "greenhouse signature" is stratospheric cooling. And guess what, that's what's been happening.

Then there is Chris Colose at Climate Change:

Tropospheric warming in the tropics is a signature of greenhouse warming, but it is more accurate to say that it is not a unique signature (i.e., you get this “hotspot” with all types of forcings).

And :

It looks to me as though experts disagree with Evans. Certainly few if any of them take seriously this unpublished and non peer reviewed essay. Of course, experts can be wrong, but clearly this paper does not “falsify” AGW as Nova claimed. The point is, Nova citing this paper as “showing that the theory has been falsified” is as clear an example of cherry picking as it is possible to make. The idea that the whole of AGW – thousands of peer reviewed scientific papers and evidence – is falsified by this one article on a web site, is just absurd. And a standard denialist / crank tactic.

Fake Experts

In Denialism Blog’s section on Fake Experts, they state that:

[real] experts have experience in their field, and they can provide answers that are consistent with the state of knowledge in that field

And that:

…a fake expert is usually somebody who is relied upon for their credentials rather than any real experience in the field at issue, who will promote arguments that are inconsistent with the literature, aren't generally accepted by those who study the field in question, and/or whose theories aren't consistent with established epistemological requirements for scientific inquiry.

So who does Nova write about excitedly on her blog? John Theon, who was supposedly James Hansen’s supervisor at NASA but who now disagrees that global warming is man made. Of course we know that Theon wasn’t actually Hansen’s “boss”, and that he retired from NASA in 1994. Theon seems like the archetypal fake expert – someone with credentials but who hasn’t worked in the field for a long while – too long to be taken seriously over current experts to be sure. Nova adopts standard denialist tactics by writing about this as though it is meaningful, just as she also appeals to this list of 650 supposed experts who dispute AGW, although we know this list is padded with TV weathermen, economists, non-climate experts, and a number who are actually not AGW “skeptics” anyway. In fact 58% of the "experts" quoted have no credentials in climate research and only 16% have top-notch credentials. Also see another debunking of this list. Compare these 650 (really less than 100) "skeptics" with the American Geophysical Union (AGU) which has 50,000 members, most of whom really are earth scientists. Only a few dozen AGU members are on this latest denier list. Again, standard denier techniques from Nova.

Impossible Expectations and Moving Goalposts

Denialism Blog defines Impossible expectations (and moving goalposts) as “the use, by denialists, of the absence of complete and absolute knowledge of a subject to prevent implementation of sound policies, or acceptance of an idea or a theory.” And guess what, the example they give is of global warming deniers:

One finds that they harp endlessly about models, how much models suck, how you can't model anything, on and on and on. True, models are hard, anything designed to prognosticate such a large set of variables as those involved in climate is going to be highly complex, and I'll admit, I don't understand them worth a damn. Climate science in general is beyond me, and I read the papers in Science and Nature that come out, blink a few times, and then read the editors description to see why I should care. But with or without models, which I do trust the scientists and peer-reviewers involved to test adequately, that doesn't change the fact that actual measurement of global mean temperature is possible, and is showing an alarmingly steep increase post-industrialization.

I don’t need to add much to that, except to state that (unsurprisingly) Nova doesn’t believe climate models are empirical evidence.

Add the list of debunked AGW skeptic arguments that the AGW “skeptics” keep repeating, and you have quite a litany of denialism. Cherry picking one non peer reviewed and unpublished paper that few if any climate scientists take seriously and claiming in all seriousness that it falsifies the whole of AGW. Reporting on lists of “skeptics” as though this actually means anything. Claiming models aren’t science. Calling logical fallacies that aren’t while relying on them herself. After this exchange I’m even more convinced of the science behind AGW. I describe the AGW skeptics as deniers because they employ denier tactics. Employ denier tactics, you’re a denier.

Evidence for AGW

Nova claims there is none. For those interested, here is some. The links are not direct to peer reviewed papers (although there are links in some of the articles to peer reviewed work). Obviously it’s not comprehensive. But it’s a good place to start and you certainly can’t claim there is “none.” Unless you’re a denier.

RealClimate is a good place to start. Also see their site index.

Coby on The Models are Unproven which includes a list of significant predictions of enhanced greenhouse gas warming that have been made and confirmed. Also How to Talk to a Climate Sceptic which also explains denier tactics.

IPCC Fourth Assessment Report. Note: the IPCC collates research published by scientists and institutions across the world – that’s thousands of peer reviewed climate science papers.

Scientific opinion on climate change – an article that documents scientific opinion as given by synthesis reports, scientific bodies of national or international standing, and surveys of opinion among climate scientists. Agreed it’s a Wikipedia page, but there are 90 links to follow.

February 18, 2009 – edited to add:

Joanne Nova just responded on her blog. I’m underwhelmed. If you want to read my reply, please scroll down to comment 105 below. (I’m sorry but links don’t work to comments on page 2 of TypePad blogs. I apologize – this has only been an open ticket with TypePad for a year or so with no resolution yet.)