Sunday, January 6, 2013

Global Warming not our fault

Recently I've had the pleasure of engaging in an online conversation about climate change in which one of the participants agrees that the Earth is possibly warming but disagrees that human activity is the cause.

"Any climatologist who tries to say they know [that global warming is cause by humans] would be lying. We have only been measuring temperature accurately since the 19th century, and there is no way one could tell the difference between human cause or natural cycle with such a short data set."
This comment deserves a response, which I will get to shortly, but first I must summarize the other objections posted.
  1. A link was posted to the HadCRUT dataset along with a note critical of one of the methods explanations, the implication being, I suppose, that the entire data set might be invalid.
  2. A link was posted to a news article about the Earth's' magnetic field fading, with a note that the following is all I need to read: "Today it is about 10 percent weaker than it was when German mathematician Carl Friedrich Gauss started keeping tabs on it in 1845, scientists say."
  3. A link was posted to Is the earth spinning slower? with the corollary that the moon is moving away from the earth by 3.8 cm/yr.
  4. A link was posted to a copy of an article DMI polar data shows cooler Arctic temperature since 1958.

Now the first thing to say is that these objections cannot, or at least should not, be dismissed with a mere wave of the hand. Not only were they offered in complete sincerity, which I appreciate, but most of them carry some weight with at least a certain segment of the population and most of them also carry a grain of truth that could be important. The next thing for me to say is that I didn't (and don't) find any of them persuasive, although I did take them seriously enough to research and write this post.

Objections (3) and (4) were offered together, the hypothesis being: (a) The moon effects oceans tides; (b) The tides influence ocean currents; (c) If there is less pull (and less angular momentum) due to the greater distance, then the currents that carry the heat away from the equator to the cooler regions will be diminished; (d) This means that more heat stays in the atmosphere instead of being sinked (sic) away to cooler waters in the ocean; (e) Thus we should see a cooling trend in the arctic, as demonstrated in the DMI data as interpreted by Lansner.

Objection (3). The distance of the moon from the earth varies over the course of its orbit from 356,700 km at perigee and 406,300 km at apogee. This is a difference of more than 12% each month (29.5 days). The grain of truth here is that when the moon is at apogee it does have less gravitational pull, which can contribute to lower variation in the high/low tide level. When the moon is at perigee there is more gravitational pull, which contributes to greater variation in the high and low tide. The problem with my interlocutor's argument is that 3.8 cm/yr over the course of even 150 years (let alone 30) is less than 0.03%. Even if we agree that averages are more important than ranges, a change in distance of << 0.1% over more than a century does not account for much. Incidentally, there are factors other than the moon's distance which affect the tides, most of which tend to dampen the moon's affect.

Objection (4). Without (3) there would be little or no explanation for (4) were it to be valid, but it needs to be considered on its own merits. So what are we to make of the fact that DMI reported an apparently cooler Arctic temperature from 1958 to present? First it should be noted that DMI itself never interprets its own data in the way that (4) does. In fact, DMI is concerned that not enough attention is being paid to the dire consequences of permafrost melting in the Arctic, but that is another matter.

What Lansner did in (4) was to take the thawing season out of context. Let me make this a simple as I can. In the winter the average temperature gets very low in the arctic (<-10 F, <-25 C) and there is much variability. In the thawing season, it never gets much above freezing (32 F, 0 C) because if it does, the ice melts cooling the air above it. In fact, let me just speculate. What if the "cooling" trend observed by the DMI is due to higher ocean temperatures or in any case a higher rate of ice melting? Pure speculation on my part, but my argument does not depend on it. The important SCIENCE is that annual average Arctic air temperatures have increased over the past few decades at a rate around twice the global average, and this is well documented. That is the crux in a nutshell, and anyone interested in the details can find them at Skeptical Science.

In a follow-up comment my interlocutor dismissed the Skeptical Science article by misinterpreting the explanations of the different datasets as a criticism of the DMI methods. True, the article discusses at length the strengths and weakness of several different methodologies, but the point was not to say that one is more valid than another. The Skeptical Science criticism of (4) is not that the DMI data should be considered invalid, but that DMI, GISS, and others all point in the same direction. The annual average Arctic temperature has risen sharply in recent decades. They all agree on this trend. Lansner (4) disagrees because he looks at only two months out of the year.

(I mean no disrespect, but can anyone tell me who Frank Lansner and Nicolai Skjoldby are, or their credentials? Apparently the latter has an M.S. in Forestry from the Royal Danish University of Agriculture, but other than that I can find nothing online about either one.)

Objection (2). The article per se is not about climate change. My interlocutor has used it, however, to offer the hypothesis that "a 10% reduction in the earths magnetosphere means a 10% increase in solar radiation to the earths surface." Uh, no. Not true. A magnetic field has no effect whatsoever on electromagnetic radiation in any part of the spectrum. What the magnetic field does, however, is protect the Earth from the solar wind (charged particles). This is important, of course, but it is unrelated to the amount of radiant energy received from the sun. — Entirely unrelated, it was suggested that somehow the fact that we only have temperature measurements back 150 years and that we have only been measuring the Earth's magnetic field for 150 years is somehow significant. First, that coincidence is not significant. Second, in both cases (temperature and magnetic fields) we have proxy measurements going back much further. The further back, of course, the less precise or reliable, but the information is still useful.

Objection (1). I am not sure (1) was actually offered as an objection, but this reminds me to begin working on a discussion of surface air temperature measurements.

Going back to the original comment, there are two aspects that each deserve a much more thorough response than I can provide this morning. The first is about the nature of science in general and climate science in particular. Scientists do not "try to say they know" anything with certainty. What they do is present the evidence and their interpretation of that evidence. The evidence is for anthropogenic global warming is strong, and most climate scientists interpret it that way. The second is that my interlocutor states emphatically that the temperature measurement record is too short to allow any climate scientist to come to a valid conclusion about the source of global warming. My only response at the moment is that (a) even 150 years of temperature data provide powerful evidence, and (b) there are many other kinds of evidence that corroborate that conclusion. (Sigh, never enough time.)

9 comments:

  1. Donnal,
    I decided to skip being speculative about the two ideas.

    Magnetic Field #1
    Receding Lunar Orbit# 2

    and send them to a PhD Climatologist. Here is his response:



    Luke:

    Idea #2 would have such tiny changes I doubt they would have any possible measurable impact. Idea #1 has some possibility, but the radiation change would impact the highest energy solar waves which have only tiny influence on the climate in general (though the higher one goes the better chance to detect something.) This may influence ozone production which has an impact on stratospheric climate.

    John R. Christy
    Director, Earth System Science Center
    Distinguished Professor, Atmospheric Science
    University of Alabama in Huntsville
    Alabama State Climatologist
    Voice: 256 961 7763; Fax: 256 961 7751
    http://www.nsstc.uah.edu/atmos/christy2011/index.html
    christy@nsstc.uah.edu

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    1. Thank you, Luke. And my thanks to Dr. Christy.

      If I understand his brief reply, it essentially confirms what I wrote in my post, especially with regard to #2. Regarding #1, I defer to Dr. Christy's expertise about "the highest energy solar waves which have only tiny influence on the climate in general." When he talks about ozone production, however, I am surprised that he did not mention protection from the solar wind (charged particles), which is well known to impact the ozone layer. In other words, weakening of the magnetic field does not account for observed global warming, but it well may influence the stratospheric climate in other ways.

      By the way, the link to Christy's web page appears to be out of service. I was able to find it at:
      http://www.nsstc.uah.edu/atmos/johnchristy/about.html

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    2. Yes, you are understanding his reply correctly. I e-mailed him because he is one of the more outspoken Climatologist that believe human's are the cause of the warming trend. I didn't want anyone thinking I would selectively find a radical climatologist that would purposely side with alternative views. I am actually surprised I even received a response at all, let alone one that says one of my ideas isn't too far out of line.

      And his e-mail link was just what came in the signature location, maybe he forgot to update it.

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  2. In addition, I found an interesting article about Dr. Christy where he addressed Congress.

    http://wattsupwiththat.com/2012/09/21/dr-john-christys-testimony-before-congress/

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    1. Thanks for introducing me to Dr. Christy's work. It will take some time for me to read and evaluate what he has written although I don't mind saying that it is a relief to read dissenting opinion from a bona fide climatologist. I am skeptical of some of the statements I have read so far (of course I have no personal expertise on which to base my doubts). On the other hand, I find three of his statements to be particularly credible and thought provoking.

      1. "Extreme events are poor metrics to use for detecting climate change. Indeed, because of their rarity (by definition) using extreme events to bolster a claim about any type of climate change (warming or cooling) runs the risk of setting up the classic 'non-falsifiable hypothesis.'"

      2. "I've often stated that climate science is a 'murky science. We do not have laboratory methods of testing our hypotheses as many other sciences do."

      3. "If the country deems it necessary to de-carbonize civilization's main energy sources, then compelling reasons beyond human-induced climate change need to be offered that must address, for example, ways to help poor countries develop affordable energy. Climate change alone is a weak leg on which to stand to justify a centrally-planned, massive change in energy production, infrastructure and cost."

      As a result of (1) in the future I will be more cautious about attributing extreme events to global warming. I'm not saying I won't ever (try to) make a connection, but I will be more cautious.

      I am not entirely convinced by (2) because there are a number of other sciences that lack laboratory methods of testing hypotheses. Nevertheless, I grant that climate science is extremely complicated, and in the future I will try to avoid unwarranted over simplification. On the other hand, defensible simplification is a good thing.

      Statement (3) is particularly telling, and it carries additional weight because Christy lived in a developing country for a while. While I believe that de-carbonization will become essential for our survival, I agree with Christy that we cannot ignore the impact of lack of cheap energy for developing countries and those in poverty around the world. I take this seriously.

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  3. I would like to comment on a few of the item points you have above.
    The HadCRUT dataset was in case we wanted to go back to the actual data for review, there was no disputing. I simply went found the source data in Michael Mann's publication and linked it for future use.
    Comments directed towards the Skeptical Science link were about it's methods of determining DMI information as invalid. The first point made by Skeptical Science is that the equipment has been upgraded over the 50 year sample time, causing inaccuracies. I find this utterly ridiculous to even suggest, since all technology used in gathering temperatures for all over the planet have been upgraded over the past 50 years. So the same error would have to be in non-polar climate data too. I don't hear much about that. And this is the type of dialog and thought process throughout the article. This isn't just mild skepticism to be overlooked. Clearly the author/interpreter is trying to build a case hoping nobody is thinking clearly enough to see how faulty it is. And who is the author of this Skeptical Science article? I can't find any real credentials on Peter Hogarth.

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    1. Touche about Hogarth. I can't find his credentials quickly either, although I've read several other of his articles and found them well-researched and well-written.

      And I'm sorry, Luke, but I don't read the article the way you do. Nowhere does he say or imply that the DMI information is invalid. He indicates that the equipment has been improved, but "These changes could be linked to minor differences in the apparent Summer melt temperature." He does not claim they are inaccurate. He is explaining discrepancies. He is not saying that any data set is invalid; he IS saying that COMPARING them is invalid. DMI agrees. (If anything, he is saying that the DMI data is BETTER because of their improvements.)

      The point of the article is NOT that we should ignore the DMI data, but that we should not focus on two summer months. We should look at the annual data.

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  4. Also I have noticed a lot of skepticism towards my idea about what the earths magnetosphere does, or even has in relation to the earths climate. While I hate to resort to Wikipedia, it's just easier to grab this short statement.

    "The Earth is largely protected from the solar wind, a stream of energetic charged particles emanating from the Sun, by its magnetic field, which deflects most of the charged particles. These particles would strip away the ozone layer, which protects the Earth from harmful ultraviolet rays. Calculations of the loss of carbon dioxide from the atmosphere of Mars, resulting from scavenging of ions by the solar wind, are consistent with a near-total loss of its atmosphere since the magnetic field of Mars turned off."

    http://en.wikipedia.org/wiki/Earth%27s_magnetic_field

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    1. That's what I said. If the magnetic field weakens to the point of allowing the solar wind to strip away the ozone layer it would be a big deal. But that is not what you said at first.

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