When I wrote a book review on the subject of climate change a few days ago, I had something in mind, but the review went in a different direction. The title actually didn't fit any more. Here are charts I made to illustrate my thinking on the terminology about "carbon pollution" and all the hype surrounding it, on both sides. Firstly, an nGram of the usage of three popular terms since 1970:
Although warming caused by the greenhouse effect, in particular that caused by carbon dioxide, was quantified by Svante Arrhenius in 1896, only after about 1970 was it brought to public attention. The great promotion of this issue really took off after 1985. This nGram shows that, in print at least, "Greenhouse Effect" was soon superseded by "Climate Change" and "Global Warning". But let's focus on a different term and its scientific synonym:
You can see from the upper chart that the term "Climate Forcing" has been scarcely a blip on the radar. But on the scale of the lower chart we see that about the time "Greenhouse Effect" peaked, "Climate Forcing" began to surge (relatively speaking), and shortly after that, "Anthropogenic Climate Change", a more scientific synonym, came along, but it is quite a mouthful.
It is a pity that Google stopped scanning books in 2008. I'd like to see how these words have fared in these past ten years. Nonetheless, I did a Google search for all these terms and a few others I've thought of in the past day or two (put in quotes to force literal searching), setting the search time to the past year, here is how they score:
- 7 - Anthropogenic Climate (allows "change" or other following words): 488,000
- 8 - Anthropogenic Climate Change: 478,000
- 6 - Carbon Pollution: 523,000
- 1 - Climate Change: 147,000,000
- 9 - Climate Forcing: 366,000
- 4 - Climate Science: 2,310,000
- 5 - Climate Warming: 975,000
- 2 - Global Warming: 56,600,000
- 3 - Greenhouse Effect: 4,360,000
- 10 - Greenhouse Warming: 295,000
The number preceding each term is its rank in this alphabetized list.
Why do people use the words they use? Impact. "Climate Change" and "Global Warming" get the public's attention. But the actual debate is not really about whether climate is changing or the globe (i.e. its atmosphere) is warming. It is about the extent that human civilization contributes to the change or the warming. However, "Anthropo..whatever" is too much of a mouthful, and "Climate Forcing" doesn't have quite the ring of the more popular terms.
But: Climate Forcing is really the best term about which to have a policy debate. The atmospheric climate will change gradually over time, whether the human race is highly civilized or goes extinct. Prior to 1975, the big worry about "Climate Change" was about "Global Cooling". A cooling trend highlighted by the first 15-18 years of weather satellite measurements triggered fears of a new ice age. And we find that the recent Solar Maximum had lower sunspot activity than most prior cycles. Based on historical records, this could indicate a cooling trend because lower solar activity heats the Earth's atmosphere less than average. Sunspot numbers are an indicator (not a cause) of the number of flares and other phenomena that send extra energy our way.
So, how big a factor is Climate Forcing? Let's call the Climate Forcing Factor the CFF. The way the media report things, one group called "climate deniers" would say the CFF is close to zero. In the same media, a group called "established science" claims the CFF is "most" or "nearly all" of the difference, in the range 50%-90%. Putting aside my conviction that the media are rather incredibly biased, we can instead identify the poles of the debate as "Large CFF" and "Small CFF" factions. Who is right? Do we have a way to know?
We don't, actually! But we can dig out an indication or two.
This article in ScienceDirect states that variations in sunspot activity account for about 40% of long term temperature rise in Norway over the past century, with a probable range of 25-56%. For a different portion of the North Atlantic, the range is 63-72%. This ought to please the Large CFF folks.
Remember the ozone hole? Starting about 30 years ago colleagues of mine at DuPont determined the great amount of damage being caused to the ozone layer some 15 miles (~25 km) overhead, and this triggered research efforts at DuPont and other chemical companies to find new refrigerants for air conditioners and new propellants for aerosol cans. The ozone "hole" was a dramatic thinning of this layer mainly over Antarctica, but spreading halfway to the equator, and there was a similar, but smaller thinning over the Arctic. But we need to be clear: the "ozone layer" isn't pure ozone; it is where ozone is concentrated to a level of about one part in 100,000 (0.001%); it is still mostly nitrogen. Ozone at sea level is around 1/30th of this, about 1/3,000,000th. Chlorine from refrigerants and propellants in use before 1980 had reduced the level of ozone over the poles by about 2/3, and elsewhere by about 20%. "Ozone hole" is the dramatic term that refers to the reduction of ozone from 1/100,000 to 1/300,000 over Antarctica during the southern summer.
Ozone is funny stuff. It is created from oxygen by ultraviolet light (UV), and then it absorbs UV, which heats it up. So the more ozone, the more the atmosphere is heated from the top. Specifically, at subtropical latitudes, surface temperature averages about 300K (27°C or 81°F), while 15 km (9½ mi) above, air temperature has fallen to about 200K (-73°C or -100°F). Ozone and other stratospheric gases absorb UV and some IR to raise the temperature back to 300K by about 50 km (30 mi) altitude. This warm gas in the mid- to upper stratosphere emits thermal radiation (longwave infrared) both upwards and downwards, which heats the air below a little. The gradual increase in stratospheric ozone levels over the past 30 years have contributed a little heating, but I have not found a rigorous analysis of the matter. "About a degree" is a general statement I have read. This is a factor that tends to please the Small CFF folks.
These things indicate that the CFF is unlikely to be greater than 50%, and is probably closer to 25% or less. I would not say, "close to zero", so I am not in the extreme Small CFF crowd, but neither do I favor Large CFF. As I have stated elsewhere, I learned that if we were to raise carbon dioxide levels to, say, ten times their present level, the amount of greenhouse heating would not exceed 4°C or about 7°F. That is quite significant. Is it enough to end civilization? I don't think so, but it will definitely change it. We are unlikely to find out, though. If we were to burn all the fossil fuels that we currently know about, it would no more than double the amount of carbon dioxide that we have already emitted. That's another way of saying that we have already burned about half the global reserve of fossil fuels. In rough terms, it means we have so far doubled atmospheric carbon dioxide, from around 200 ppm to around 400 ppm. Once we run out of natural gas, oil and coal—should we continue freely burning them—the level could become around 600 ppm. I don't think we have enough fossil fuel available to push that to 1,000 ppm, where some people begin to feel the effects.
For all that, we must continue to find other sources of energy, on all fronts. No source of energy is perfect. Wind farms (currently 4% of global electricity generation) disturb wind patterns, heat the air that passes through the fan blades, and kill migrating birds; solar panels turn about 15-20% of sunlight into solar energy and the rest is turned into heat, and much of this would be in desert areas where the sand usually reflects 75% of the light right back out into space; geothermal energy is "clean" from a heat perspective, because the heat will emerge from the earth anyway, but using geothermal energy causes pollution of surface water and ground water, a whole lot of pollution; and so forth. The more we learn about all these things, the better we can select energy generation methods that cause the least harm. That, and that alone, will reduce the CFF. It will probably never be zero, until human population is zero.
Postscript: Do you know what the global average temperature is? I am a geophysicist. Including the whole planet, the average temperature is about 4,000K (over 7,000°F). We need a different term for "global average atmospheric temperature", and we need to always specify at what elevation; is it surface, or at the average elevation of continental plains (about half or 2/3 a kilometer), or some other "standard" height?
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