Clean Air Causing Global Warming?

It seems that the leading man-made cause of global warming is environmentalism; specifically, efforts to improve air quality by reducing pollution, New Scientist reports.

Since 1980, average air temperatures in Europe have risen 1 °C: much more than expected from greenhouse-gas warming alone. Christian Ruckstuhl of the Institute for Atmospheric and Climate Science in Switzerland and colleagues took aerosol concentrations from six locations in northern Europe, measured between 1986 and 2005, and compared them with solar-radiation measurements over the same period. Aerosol concentrations dropped by up to 60 per cent over the 29-year period, while solar radiation rose by around 1 watt per square metre (Geophysical Research Letters, DOI: 10.1029/2008GL034228). “The decrease in aerosols probably accounts for at least half of the warming over Europe in the last 30 years,” says Rolf Philipona, a co-author of the study at MeteoSwiss, Switzerland’s national weather service.

Say Anything‘s Piligrim finds this terrifically amusing:  “Well now, there’s a moral dilemna for you. If we go back to eating roots and berries and living in pre-industrial all natural bliss, one with nature and all that, we might end up with a warmer planet than if we just went ahead and enjoyed ourselves.”

Of course, clean air is a good thing in and of itself.  I was, however, under the impression that the rationale for getting rid of aerosols (or, more accurately, the hydroflourocarbons that propelled them) was because we thought they were destroying the ozone layer and thereby increasing harmful ultraviolet rays from the sun.  It would be quite odd, indeed, if our solution to the problem yielded the same results in a different way.

UPDATE:  Commenters tell me that, in this case, aerosols have nothing to do with aerosol spray cans but simply particulates in the air.  Oddly, the report in New Scientist Environment is entitled “Cleaner skies explain surprise rate of warming” and the linked abstract is unhelpful. Is the Web headline misrepresenting the article itself?

I’ve updated the headline and illustration to eliminate confusion, although I remain somewhat confused as to what the study actually reports.

UPDATE II: A reader has sent me a PDF copy of the entire journal article which I’ve uploaded here.  I’ve made a quick scan and, frankly, still don’t understand it.

Illustration:  NASA Earth Observatory

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James Joyner
About James Joyner
James Joyner is a Security Studies professor at Marine Corps University's Command and Staff College and a nonresident senior fellow at the Scowcroft Center for Strategy and Security at the Atlantic Council. He's a former Army officer and Desert Storm vet. Views expressed here are his own. Follow James on Twitter @DrJJoyner.


  1. Anon says:

    The word aerosol in the New Scientist article is referring to particles in the air. So, getting rid of CFCs is to help the ozone layer, yes. But that is different from efforts to reduce aerosol concentrations in the air. These come from many sources, but CFCs are not aerosols.

  2. Anon says:

    Also, note that reduction in the ozone layer will increase UV radiation, but the primary concern about this is not global warming, but rather all the damaging effects of UV on organisms.

    However, James main point about two counter-acting effects is at least partially on target. Reducing greenhouse gases by reducing the use of fossil fuels could reduce aerosol emissions.

  3. Dave Schuler says:

    Anon beat me to the punch. In this context aerosols means, basically, all air pollution.

  4. Steve Plunk says:

    James, it means whatever the AGW crowd wants it to mean. Cooler temperatures mean global warming, growing glaciers on Mount Shasta means global warming, actual data not matching computers models means global warming. It’s not about science, it’s about achieving leftist goals that could not be achieved through the standard political process. This is a classic type of threat Hayek warned us about. We must give up basic freedoms to the state in order to confront the threat.

  5. Anon says:

    James, the New Scientist headline seems accurate. The academic article is talking about particulates (aerosols) in the air. It is true that reduced particulates increase warming.

    However, it is not true that reduced CFCs (aerosol propellants, as you stated) lead to increased warming.

    So, it is true that cleaner skies lead to more warming, but the cleanliness is due to efforts to reduce particulates, rather than efforts to reduce CFCs. Thus, your irony is more or less valid, just for a slightly different reason.

  6. Zelsdorf Ragshaft III says:

    Looks like only one poster here gets it. Does not, in a situation we call global warming, the temperature actually have to rise? The newspaper I get shows the temperature daily. They also show the highest temperature, historically for that day. I don’t know about the rest of the world, but here in Sacramento, CA we are NOT experiencing global warming. But, for you that are interested. I am selling carbon credits for half the price Algore sells them.

  7. Spoker says:

    Wow! Who are we going to have to pay to put all the junk back in the air so we can get back to the good ‘ol days of global cooling? And will it require and new tax to pay for it?

  8. Spoker says:

    And by the way, does anyone know when the various native arctic populations will start paying their fair share of carbon credits and global warning taxes on all the emissions from all the new volcano’s that have been discovered under the arctic ice cap. Fair is fair, at least we some scientific proof they exist.

  9. Anon says:

    One last comment. Part of the reason for the confusion is that CFCs are propellants for household sprays, which do in fact produce aerosols. But the goal of CFC reduction is to reduce the damage in the air caused by CFCs, not to reduce the contribution of household aerosols to atmospheric aerosols. Also, it seems that household sprays don’t contribute much to atmospheric aerosols, as your graphic indicates.

    Additionally, CFCs are not themselves aerosols, since they are gases (at atmospheric pressures), not particulates.

  10. Anon says:

    Zelsdorf, the fact that the record daily high temperature occurred in a previous year does not say much about whether or not it is warming in Sacramento.

    That’s not to say that a more detailed, quantitative analysis of record high temperatures would be meaningless. Just that that mere qualitative fact alone is not enough to disprove warming in Sacramento.

  11. Bruce Moomaw says:

    Yup; there is no doubt at all that CFCs are greenhouse enhancers — and incredibly efficient ones, hundreds of thousands of times more efficient than CO2. (Dr. Chris McKay has actually proposed using them at some point in the not-too-distant future to warm up Mars and make it habitable.)

    Aerosol particles are an entirely different matter, and whether they increase or decrease global warming depends on what their albedo at different wavelengths is (e.g., whether they’re light or dark in color in visible light — and in the infrared). Sulfate mists — such as those given off by volcanoes, and by some forms of smog — are anti-greenhouse and so cool the planet; they’re light-colored and reflect incoming sunlight back into space, but they’re transparent to IR coming up from below and so let it escape back into space. This is actually officially called the “anti-greenhouse effect”. (It’s now generally believed that the above-average volcanic activity in the third quarter of the 20th century explains the temporary slack-off of global temperature rise in that period.)

    Cumulus clouds — made out of liquid water droplets — also have an anti-greenhouse effect, but a tremendously weaker one. Cirrus clouds — made of solid water ice crystals — have the opposite effect: water ice is translucent in visible wavelenghts but actually dark-colored in the infrared, so cirrus clouds warm up the planet. (The possible changes in the balance of cirrus to cumulus clouds on Earth as a whole is one of the chief remaining uncertainties in the climate debate, and just about the only possible mechanism GW skeptics can come up with as to why our CO2 increase might conceivably NOT warm up the planet — if we’re very, very lucky).

    And then there’s soot from fires — which of course is black, absorbs visible light like crazy and re-emits it as IR, and is a definite greenhouse increaser. That’s one case in which economic development of the Third World unquestionably would also take a chunk out of GW. Unfortunately, the additional amount of CO2 pumped into the air by a developing Third World — unless and until we can come up with technological countermeasures — will vastly outweigh the anti-GW benefits from its getting rid of primitive cookfires and industrial forges. Which is why we need to get cracking on the development of those countermeasures.

    And in that category, there actually is one rather wild idea floating right now that it might be worthwhile to deliberately dump large amounts of sulfate mists into the air — IF we can’t find any better countermeasure. In fact, the proposer is Paul Crutzen, winner of the Nobel Prize in Physics for his unravelling of the precise nature of man-made ozone destruction. “A few years ago I would have said, ‘I’m not touching that.’ ” Now he’s getting so desperate about the apparent lack of willingness of humanity to develop any other countermeasures that he’s talking about this one. See the Oct. 20, 2006 “Science, pg. 401 (again not available for free on the Web, dammit) and his article in the August 2006 “Climatic Change”.

  12. Triumph says:

    Is the Web headline misrepresenting the article itself?

    No, I think the problem is that you tried to comment authoritatively on a technical issue in an area outside of your expertise.

    Please don’t let this deter you, however, from further posts on environmental science–they are always good for a chuckle.

  13. William d'Inger says:

    And then there’s soot from fires — which of course is black, absorbs visible light like crazy and re-emits it as IR, and is a definite greenhouse increaser.

    Um, are you sure about that? What about nuclear winter? Scientists claimed the soot from burning cities of a global nuclear war would drive temperatures so low that crops would fail, and whoever didn’t die from radiation would starve to death. Personally, I think Steve Plunk has got it right.

  14. Anon says:

    William, I don’t think anyone is sure. During the Kuwait oil fires, temperatures dropped in the area. Volcanic eruptions are also documented to cause cooling.

    I find the way politics aligns with risk to be interesting. For example, why is it that the left seems to be more concerned about the danger from global warming and chemicals, while the right is more concerned about the danger of terrorism? How much of this is due to real differences in the way that liberals and conservatives think, and how much of this is due to history and group identification?

  15. William d'Inger says:

    I find the way politics aligns with risk to be interesting

    That’s my point exactly. Back when the fear was global cooling, science (supposedly) proved that soot would worsen the problem by cooling the earth even more. Now that the fear is global warming, science (supposedly) proves that soot worsens the problem by warming the earth even more.

    I can’t be the only person who smells a rat. These people have long used science solely as a means to push their political agenda, but when President Bush draws scientific conclusions in the opposite direction, these same people go plum crazy. OK, children, can anybody spell:

  16. Michael says:

    Um, are you sure about that? What about nuclear winter? Scientists claimed the soot from burning cities of a global nuclear war would drive temperatures so low that crops would fail, and whoever didn’t die from radiation would starve to death.

    Ash clouds would block radiation from reaching the ground, but black particles would not reflect it back into space either, so the heat would just be trapped in the upper levels of the atmosphere.

  17. Anon says:

    But note that during the Kuwait oil fires, the temperature in the region dropped. Also, the nuclear winter scenarios postulate drops in surface temperature, and soot is a significant part of the scenario.

    It’s complex. Soot is dark, true, but if it heats up enough, and at high altitudes, it would re-radiate a certain amount of energy back into space. You can formulate two thought experiments. Suppose all the soot was formulated into a huge sheet 500 miles above the earth, and furthermore assume that there was a highly reflective layer of ice crystals far below it. This would almost certainly reduce surface temperatures. The soot would absorb light, and in the process heat up until the energy it re-radiates as black body radiation is equal to the absorbed energy. (Assume for the purposes of this thought experiment that it does not decompose or react.)

    On the other hand, suppose the soot was formulated into a huge sheet at 1 meter above the surface. This would increase surface temperatures. The soot would still heat up and re-radiate, but since it so close to the surface, much of the heat will be conducted to the air and ground.

    Another way to think about this is to imagine a greenhouse. If you throw a bunch of black stuff on top of the greeenhouse, on the outside, the greenhouse will cool. (Assuming that it does not provide any significant insulation.) On the other hand, if you put the black stuff inside the greenhouse, it will warm the greenhouse.

    In reality, we don’t have a simple structure like the glass in the greenhouse. We have this very complex, dynamic structure known as the atmosphere, and the soot is flowing around inside of it in different layers, etc. So, the soot interactions are much more complex and dynamic. That’s why there are different possible effects due to soot.

  18. Michael says:

    Not to be pedantic, but soot doesn’t technically qualify as a black body.

  19. Craig says:

    It seems that the leading man-made cause of global warming is environmentalism; specifically, efforts to improve air quality by reducing pollution, New Scientist reports.

    (Emphasis added.)

    No it doesn’t. You made that up/misread the article. The (New Scientist) article talks about warming in Europe, which is a pretty small part of the globe. It doesn’t address global warming at all.

  20. c. wagener says:

    If reduced air pollution does increase warming, the affect must be limited and not a particularly large concern. We can only get the air so clean, consequently the warming do to this would plateau.

  21. G.A.Phillips says:

    Global warming is caused by the lie of evolution taught by liberals as the truth, it’s that simple.

  22. Bruce Moomaw says:

    Talking about Mr. Joyner’s confusion over the scientific (as opposed to the lay) meaning of the term “aerosol”: If you want a scientific term that REALLY has the potential to confuse laymen, the most famous (and destructive) case is unquestionably the fact that “theory”, in the scientific sense of the word,doesn’t necessarily mean “something that isn’t proved yet”. Thus all the confusion over “the theory of evolution”.

    My own sentimental favorite, however, is “elastic”, which — so help me God — means “hard, unbending and brittle” when you’re taking about the crust of a planet. (Its opposite case in this situation is “viscous”.)