Debunking Denialism

Also see An Open Letter to Libertarian Climate Change Denialists.

The well-known Internet philosopher, atheist and market anarchist Stefan Molyneux (whose stance of psychiatry was previously discussed here and here) recently subbed for Peter Schiff on the Peter Schiff radio show. The show features discussions about global warming, gold companies, the value of philosophers over politicians and the important similarities between republicans and democrats. The section on global warming contained an interview with the mathematician and engineer David Evans. Evans has some issues with mainstream climate science that I think is worth critically examining.

To be honest, I am by no means an expert on climate science, climate modeling, ice cores, tree rings or anything like that. Therefore, I completely accept that I can be in error here. After all, when it comes to climate science, I am just a guy on the Internet. With that said, I do think I can present some thoughtful comments on the statements made by Evans and Molyneux during the interview. The entire interview can be found here, starting at about 16:12. I will quote directly from the video and leave timestamps so you can check it out for yourself. I also accept that I may have made some mistakes in this rush transcript as they talk fairly fast and sometimes it is hard to hear when the direction of a sentence is changed in the middle of words.

The introduction to the interview given by Stefan Molyneux suggests that he accept that carbon dioxide is a greenhouse gas and that an increase in the concentration of carbon dioxide increases global temperature (16:42). So far, so good. This is an important conclusion that some groups that reject the mainstream position on climate change does not even accept. So from that standpoint, it is refreshing to hear.

Climate scientists have taken into account both natural and anthropogenic forcings

The first argument put forward by Evans is this (17:54):

Molyneux: Let’s talk a little bit about this amplification thing. I’ve read quite a bit about global warming. I’ve never come across this idea before. It seems pretty important and I wonder if you can illuminate us, please?

Evans: It is the whole ballgame Stefan. The other side do not like to talk about it because the evidence runs the wrong way for them. I’ll give you the big picture. Here is how it works: when the global warming…CO₂ theory was being developed in the 1970s, they looked back and said “look, from the beginning of the Industrial Revolution 17-1850 to modern times, the CO₂ level has risen by this much and the temperature has risen by that much. OK we know, from theoretical calculations that pretty much everyone agrees on, how much warming CO₂ causes directly just as a result of the extra CO₂ in the atmosphere and that direct effect only accounted for a third of the temperature rise. OK, so we know the CO₂ level warming since 17-1850 but it only accounted for a third of the observed temperature rise. Now, here is the big jump in logic: the theorists said “Alright. Well, we cannot think of any other cause of global warming. We know it is not solar, the sun being brighter or warmer, because although the sun fluctuates a tiny bit, but not nearly enough to account for the extra warming. So therefore, there must be some amplification and this amplification due to water vapor feedbacks because the earth reacts to that extra CO₂ warming in the atmosphere by evaporating water from the oceans, creating more clouds etc. and that must amplify that warming to account for the extra warming we saw. Right, so the direct effect only gives you a third of the observed warming, so there must be amplification by three to account for the rest, because we assume that CO₂ is the only thing driving the Earth’s temperature. Are you with me so far, Stefan?

Molyneux: Absolutely.

As far as I can understand the argument, Evans is saying that everyone agrees that CO₂ causes a certain level of warming. This warming is, however, just a certain percentage of the observed warming. So therefore, climate scientists invented the idea that there must be amplification effects from the increase in CO₂ to account for the totality of observed warming.

This is an erroneous argument for several reasons. First, scientists have long since accepted that there are many different forcings besides just human emission of carbon dioxide and that there also exists radiative forcings from natural sources. For instance, figure 2.4 in the Synthesis Report from 2007 shows that human forcings include carbon dioxide, methane, nitrous oxide, halocarbons, stratospheric and tropospheric ozone, stratospheric water vapor from methane, surface albedo from black carbon on snow, surface albedo land use, direct effect from aerosols and cloud albedo effect. Not all of these are positive. Natural forcings, as detailed in the Working Group I part of the Fourth Assessment Report, includes solar variability and explosive volcanic activity.

Second, natural forcings alone cannot account for the observed warming. Yet, when scientists take into account both anthropogenic and natural forcings, these can account for the observed warming very well (figure 2.5 in the synthesis report linked above).

Third, we know that feedback processes occurs. When it gets warmer, there are more water vapor in the atmosphere, which in turn increases temperatures, which in turn release more carbon dioxide from the oceans. This is basic chemistry, not some ad hoc maneuver. While it is true that the precise effects of these may be less certain than other aspects of climate change, well-defined error bars is not the same as the notion that no conclusion can be drawn. Read more of this post