This article is Part III of my series on Robert Carter’s, or R.M. Carter’s, or Bob Carter’s paper “The Myth of Dangerous Human-Caused Climate Change.” Part I is a fairly light introduction. Part II digs into some of Carter’s talking points, notably his claims that we don’t have a theory of climate and hence, so it seems, shouldn’t be bothering with climate change too much until we do. In this one, I address Carter’s statements about carbon dioxide, found under the subheader of “Is Carbon Dioxide a Dangerous Pollutant?” in his paper.
As the subheading suggests, Carter makes a lot of the idea that CO2 is not a pollutant and seems to rejoice in the “constant exasperation” this fact causes to “those environmental activists who fear global warming”. His position rests on two major points, as I read it. The first of these is the idea that carbon dioxide has been in Earth’s atmosphere for a very long time, to understate, and that it’s levels have fluctuated a great deal over those many years. He is correct in these claims. Atmospheric CO2 has been in the atmosphere since the Earth had an atmosphere, essentially, and its levels have risen and fallen over the hundreds of thousands to hundreds of millions of year time frames that he discusses.
To support his case Carter mentions several studies that suggest CO2 levels in the recent past– within the Holocene– of “at least the present day (post-industrial) value of 380 ppm. Carter does not mention that other similar studies, including for example this one by some of the same authors he himself cites, show significantly lower numbers. He also does not mention that still other data, for example that coming from EPICA, suggest that CO2 levels are now the ‘highest for 650,000 years‘. This all leads me to think that Carter is, much as with his legendary “global warming stopped in 1998” claim, cherry picking data.
To buttress his point, Carter reaches further back in time to the early Cenozoic, 60 million years ago is the precise mark he mentions, and eventually references the entire Phanerozoic– a span of around 500 million years. The planet in virtually every aspect has changed dramatically over these time frames. Reaching back through that kind of time to find higher than today’s CO2 levels and then claiming that high CO2 levels are nothing to worry about is a bit like a 95 year old triple bypass heart patient trying to argue that his high cholesterol isn’t dangerous because its the lowest its been in 60 years. Too much has changed to make that kind of lock-step comparison. What is clear, though, is “that the atmospheric CO2 greenhouse mechanism is a major control on climate over very long time scales.”
The second leg of Carter’s position on CO2 rests upon the idea that “carbon dioxide is the staff of life for earth’s biosphere”. Plants depend upon it. We depend upon plants. CO2 levels as high as 1000 ppm, he states, have been shown to be beneficial for plant growth. Hence, apparently, CO2 is not dangerous and is not a pollutant but instead is overall a Good Thing™.
Feces is likewise part of the environment. Plants depend upon it. Bacteria break it down into chemical components that form the basis of the rest of the organic processes on the planet. We couldn’t survive without it. Without feces and its decay Earth’s life cycles would stop after one go-round. Yet concentrate large amounts of animal waste in a small area and it is a pollutant, and is dangerous. A similar argument can be made with salt, or with oxygen– which, in fact, apparently poisoned most of Earth’s first inhabitants. Really, the term ‘pollution’ is short-hand for ’something that alters an ecosystem in a bad way’. Just about anything in high concentrations will alter an ecosystem, so Carter’s appeal to “its always been around, and plants need it” falls rather flat. He fails to, or refuses to, recognize that whether or not something is a pollutant has a lot to do with concentration.
But that only covers part of Carter’s point. He argues, or strongly implies, that CO2 is beneficial for plant growth, thus it is beneficial all around. Returning to my previous example, dumping large amounts of sewage into a river would beneficial for plant growth, notably algae, in that river. Can we conclude that such growth is beneficial all around? I don’t think so. Carter makes the mistake of arguing that it would be necessarily beneficial, which is absurd. It is true that higher CO2 would likely result in an increase in plant growth, but whether this would be beneficial for humanity as a whole is the real question.
I’ve seen arguments claiming that a warmer planet would be a better thing anyway, that a warmer climate will provide more cropland and longer growing seasons and other such happy things. Maybe, but that is a tough call. What isn’t such a tough call is that if the climate changes so does the distribution of farmland. And it doesn’t take a lot to create big problems. A changing distribution of farmland means global economies change. Changing economies mean turbulence and turmoil and, usually, blood. You might end up with something more conducive to human habitation when everything shakes out, but the transition will be messy and there is no guarantee that the end will in fact be an improvement. The US, now a major agricultural producer, may end up with little to nothing arable. The famous Bread Basket is a titch on the drought-ie side as it is. But who knows? Do you want to gamble?
Overall though, the issue of whether CO2 is a pollutant or not is a rather spurious point, and Carter seem to realize this as toward the end of his section on carbon dioxide he recognizes that the gas “absorbs space-bound infrared radiation, thereby increasing the energy available at Earth’s surface for warming or increased evaporation”. This, of course, is the real issue. Call CO2 a pollutant or not, the real issue is what kind of changes an increase in the gas will cause, and what effects it will have on humanity. By admitting to CO2’s function as an absorber of radiation he admits that increasing concentrations of CO2 can at least potentially alter Earth’s temperature and by implication admits that such alteration could effect humanity. But that is not to say that he admits that raising CO2 levels will alter Earth’s temperature. This he denies by appealing to an often repeated but utterly flawed argument that tends to bear the name ‘the saturation argument’ or something similar. It runs like this, quoting Carter: “the relationship between increasing carbon dioxide and increasing temperature is logarithmic, which lessens the forcing effect of each successive increment of carbon dioxide”. Since the Earth’s atmosphere is already full of carbon dioxide– nearly saturated–, increasing it just a bit more doesn’t matter much. The effects will be too small to worry about. Unfortunately for Carter and for all those citing ’saturation’, the ’saturation argument’ is based upon a remarkably simplistic conception of the way that CO2 in the atmosphere absorbs radiation. I won’t run through the whole argument but “it is only the wavelength range between about 13.5 and 17 microns (millionths of a meter) that can be considered to be saturated. Within this range, it is indeed true that adding more CO2 would not significantly increase the amount of absorption. All the red M&M’s are already eaten. But waiting in the wings, outside this wavelength region, there’s more goodies to be had. In fact, noting that the graph is on a logarithmic axis, the atmosphere still wouldn’t be saturated even if we increased the CO2 to ten thousand times the present level.”
Note: “… the atmosphere still wouldn’t be saturated even if we increased the CO2 to ten thousand times “.
The final point Carter raises about CO2 that I have not addressed concerns the lag in climate records of carbon dioxide concentrations behind temperature. I wrote in a comment not too long ago that “CO2 is a blanket, not a heater. It doesn’t heat the Earth, per se. Instead it makes surface temperatures go up by trapping heat, much the way blankets work. The heater is something else. The heater is the Sun, and because the Earth/Sun system is so complicated a lag isn’t all that surprising.” Why isn’t that lag surprising? A blanket isn’t going to do anything until a heat source underneath it starts to raise the temperature. A blanket traps heat. It doesn’t create heat. That means that the temperature under the blanket ought to lead. This doesn’t change the fact that the blanket traps heat and it doesn’t change the fact that more blankets trap more heat.
A point that needs to be made is that while it is true that in deep history CO2 have trailed behind temperature, in recent history the reverse is true. Our carbon dioxide outputs have outstripped the ‘blanket’ effect. We’ve piled on blankets quicker than they can trap heat meaning that to some extent we are already committed to higher global temperatures.
Come back for Part IV: Can Computer Models Predict Climate?