Debunking Climate Denial

A Torrent of Errors in David Evans Case Against Global Warming


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.

Scientific evidence for tropospheric hot-spot

Evans then starts bringing up a well-known climate “skeptic” gem know as the supposed lack of tropospheric hot-spots (21:12).

Evans: Now, the amplification that is occurring would exhibit itself, and it does in all the climate models, as lot of warming, in particular there is a great deal of warming over the tropics about 10 km up. That is because the theory of amplification says “well, there is extra warming due to CO2, therefore there must be more evaporation. That happens mainly in the tropics over the oceans. That creates more water vapor. Water vapor is itself the main greenhouse gas, so that causes even more warming. There is your amplification. That extra evaporation, as the water rises into the high troposphere about 8-10 km up, it must therefore condense that release a great deal of heat. That causes the hot-spot or so the extra water vapor pushing the layer of warm water vapor higher into the atmosphere where it was previously cool and dry air. So that part of the atmosphere also becomes warmer. So the weather balloons are up there measuring where the atmosphere is getting warmer and by 1998 or so the results were pretty clear. There is no so called hot-spot over the tropics about 10 km up. Not at all, not even a small one.

Molyneux: Now, sorry, again I’m no climate scientist to say the least, but my-looking-out-the-window-weather-brain says “well if you get more water vapor in the air, doesn’t that create clouds that will reflect sunlight away from the earth, thus countering the effects of increased water moister in the air. Is that way of base, or is that vaguely possible?

Evans: Stefan, you are a better climate scientists than most of those who hold the jobs.

First, it is true that more water vapor in the atmosphere creates more clouds, but this is not enough to counter all of the increase in temperature due to the increase in water vapor. According to the Synthesis Report linked above, the cloud albedo effect is about -0.7. According to Held and Solden (2000), the water vapor feedback basically doubles the sensitivity of surface temperature to carbon dioxide. Skeptical Science also explains the limitations with Molyneux’s reasoning in Explaining how the water vapor greenhouse effect works:

Unlike external forcings such as CO2 which can be added to the atmosphere, the level of water vapour in the atmosphere is a function of temperature. Water vapour is brought into the atmosphere via evaporation – the rate depends on the temperature of the ocean and air, being governed by the Clausius-Clapeyron relation. If extra water is added to the atmosphere, it condenses and falls as rain or snow within a week or two. Similarly, if somehow moisture was sucked out of the atmosphere, evaporation would restore water vapour levels to ‘normal levels’ in short time.

Many that reject the climate science mainstream position seem to think that global warming requires a tropospheric hot-spot. However, the fingerprint of warming was actually stratospheric cooling coupled with tropospheric warming. Skeptical Science explains again:

The mistaken belief in “skeptic” circles is that the existence of anthropogenic warming somehow hinges on the existence of the tropospheric “hot spot”- it does not. Period. Tropospheric amplification of warming with altitude is the predicted response to increasing radiative forcing from natural sources, such as an increase in solar irradiance, as well. Stratospheric cooling is the real “fingerprint” of enhanced greenhouse vs. natural (e.g. increased solar) warming.

With respect to the existence of tropospheric hot-spot over the tropics:

Satellite measurements match model results apart from in the tropics. There is uncertainty with the tropic data due to how various teams correct for satellite drift. The U.S. Climate Change Science Program conclude the discrepancy is most likely due to data errors.


Satellite measurements do show warming in the Tropsphere when a cooling bias from the Stratosphere is removed. Warming trends agree well with surface temperatures and model predictions except near the Poles. Differences between various analyses are largely due to analysis techniques and compensations for satellite data issues.

Allen and Sherwood (2008) shows that thermal winds provide evidence for a tropospheric hot-spot over the tropics:

Climate models and theoretical expectations have predicted that the upper troposphere should be warming faster than the surface. Surprisingly, direct temperature observations from radiosonde and satellite data have often not shown this expected trend. However, non-climatic biases have been found in such measurements. Here we apply the thermal-wind equation to wind measurements from radiosonde data, which seem to be more stable than the temperature data. We derive estimates of temperature trends for the upper troposphere to the lower stratosphere since 1970. Over the period of observations, we find a maximum warming trend of 0.65plusminus0.47 K per decade near the 200 hPa pressure level, below the tropical tropopause. Warming patterns are consistent with model predictions except for small discrepancies close to the tropopause. Our findings are inconsistent with the trends derived from radiosonde temperature datasets and from NCEP reanalyses of temperature and wind fields. The agreement with models increases confidence in current model-based predictions of future climate change.

Warming and increase in CO2 interact with each other

At 25:01, they bring up another classic global warming denialist claim: since CO2 lags temperature after coming out of the last ice age, therefore CO2 cannot be the current main driver of climate change.

Molyneux: What else is there that might explain this historical evidence that the temperature increases almost a millennium before CO2 increases?

Evans: What high-school students learn about in chemistry called Henry’s law. That is to say, the amount of dissolved gas over a liquid depends on the temperature of the liquid. The liquid gets cooler, more gas is absorbed, but if the liquid is warmed, it release more gas. That is all that’s happening. And the higher resolution ice cores that got resolution of data points of tens of years apart, they started coming in around 1998 and they showed quite clearly as you said that the temperature went up first, and the CO2 followed, not the other way around.

The problem here is obvious: there is no contradiction between saying that CO2 was not the main driver of climate change just after the last ice age, but that it is one now. Skeptical Science explains:

When the Earth comes out of an ice age, the warming is not initiated by CO2 but by changes in the Earth’s orbit. The warming causes the oceans to release CO2. The CO2 amplifies the warming and mixes through the atmosphere, spreading warming throughout the planet. So CO2 causes warming AND rising temperature causes CO2 rise. Overall, about 90% of the global warming occurs after the CO2 increase.

So increased temperature leads to increased in CO2, which then causes more warming (since they accepted that CO2 cause warming earlier in the video). So in the previous argument, Evans and Molyneux reject the notion of amplification, but now they seem to be using it in their efforts to reject modern climate science. Contradictory, to say the least.

Why do Evans and Molyneux reject climate science?

Here is the internal argument I think they are consciously or unconsciously objecting to.

P1. If the mainstream position of contemporary climate science is supported by solid empirical evidence, then increase in state power is required to combat climate change.
P2. The mainstream position of contemporary climate science is supported by solid empirical evidence.
C. Therefore, an increase in state power is required to combat climate change.

Libertarians and free market anarchists do not like the conclusion, so they have to find a premise to object to. Usually, this is P2. Their reasoning is probably that there is no need for an increase in state power to combat something that does not exist. So they avoid the conclusion. The drawback with this approach is that they have to deny the science, which generally does not go well with friends of science, thereby making libertarians look like wacky republicans. There is, however, another option. One could take the route that free market solutions to climate change is more effective than those proposed by governments and that these also do not require the initiation of the use of force. This way, one could accept the mainstream scientific position that humans are an important contributing factor to climate change and global warming, but not be forced to accept the conclusion that more state power is required.

To say that free market solutions will be better is an empirical claim, but it is a more respectable position to take than to deny the science and it also helps to avoid making libertarians look cooky.


Debunker of pseudoscience.

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