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An Astronomical Perspective on Climate Change


Ice cores and deep sea bed cores provide the best available record of changes in global temperature and CO2 content of the atmosphere going back 800,000 years. The data shows a clear periodicity in global temperatures which is thought to be linked to the Milankovitch cycle.

Back in 1920, Milutin Milankovitch, a Serbian mathematician, proposed that fine changes in Earth’s orbit around the Sun could explain an approximately 100,000 year cycle in glaciation seen from geological evidence. The tilt of the Earth’s axis swings slightly over a 41,000 year cycle – the eccentricity of Earth’s orbit moves from almost circular to more elliptical and back again over a 413,000 year cycle – and overlaying that you have not only the precession of the equinoxes, which is an inherent wobble in the Earth’s axial spin over a 26,000 year cycle, but also a precession of the whole of Earth’s orbit over a 23,000 year cycle.

Ice core data does show a rough concordance between glaciation and the synchronicity of these orbital cycles. Even though there’s no significant change in the mean amount of solar radiation reaching the Earth over the period of its annual orbit – the orbital changes can lead to increased polar shadowing and cooling.

Once ice does start advancing from the poles, a positive feedback loop can develop – since more ice increases the albedo of Earth’s surface and reflects more of the Sun’s heat back into space, thus reducing mean global temperatures.

ice coreIt’s thought that what limits the ice advancing is increasing CO2 in the atmosphere – which can be measured from trapped bubbles of air in the ice cores. More ice formation leads to less exposed land area for photosynthesis and silicate rock weathering to remove CO2 from the atmosphere. So the more ice that’s formed, the more CO2 accumulates in the atmosphere – which causes mean global temperatures to rise, which limits ongoing ice formation.

Of course the opposite is true in an ice-melting phase. Ice melting also follows a positive feedback loop since less ice means less albedo, meaning less solar radiation is reflected back into space and mean global temperatures rise. But again, CO2 becomes the limiting factor. With more exposed land, more CO2 is drawn from the atmosphere by photosynthesizing forests and rock weathering. A consequent drop in atmospheric CO2 cools the planet and hence limits ongoing ice melting.

But there lies the rub. We are in an ice-melting phase of the Milankovitch cycle now, where the Earth’s orbit is closer to circular and the Earth’s tilt is closer to perpendicular. But CO2 levels aren’t declining – partly because we’ve chopped a lot of trees and forests down, but mostly because of anthropogenic CO2 production. Without the limiting factor of declining CO2 we’ve seen in previous Milankovitch cycles, presumably the ice is just going to keep on melting as the albedo of the Earth surface declines.

Projected changes in coastlines with 170 metre sea level riseSo you might want to rethink that next coastal real estate purchase – or hope for the best from Copenhagen.

Comments on this entry are closed.

  • Hon. Salacious B. Crumb December 8, 2009, 9:10 PM

    I agree. I was interested to see how far this guy would go – even with the most ridiculous and annoying attacks.

    It is extraordinary to think that one’s mindset is so fixated that it cannot sort out things in degree and deal only in terms of absolutes, and worst, their absolutes! .

    I presented a logical argument, and the only hole he found was;

    “The changes in CO2 is caused by Man, who is contributing ON TOP OF the natural changes by astronomical means. With or without influences by Man the climate can change within decades.With the addition of EXTRA CO2 by Man’s own activities, can make the chaotic system even more chaotic.”

    Then his reply is;

    Your are misguided and there is no real science to prove that.

    It is an extraordinary omission. Clearly you don’t just need science to prove that. There is overwhelming evidence CO2 is rising AND burning, say coal, is adding to it. Also weather systems (and climate) are undeniably chaotic systems I.e. They cannot be predicted with certainty more than several days in advance.

    ..and yet the denier of climate changes says this view is “misguided.” If simple logical fails, then there is no chance that individual like this one can formulate an intelligent or contributory view. (it is exactly like a certain snake man I know)


  • 2ru_press December 8, 2009, 9:30 PM

    Yeah! AL GORE!

  • Hon. Salacious B. Crumb December 9, 2009, 12:00 AM


    Yeah! JACKASS!

  • Lawrence B. Crowell December 9, 2009, 6:54 AM

    The conservative mentality which transitions into right winged behavior is an example of the authoritarian personality


    which was outlined by Theodor Ardorno. This study was completed in a review of the social psychology behind the Nazi government of Germany in 1950. John Dean has included these analyses in his “Conservatives Wtihout Conscience,” in looking at the GW Bush period.

    Of course this does not necessarily imply conservativism, for it can work with extreme leftist political ideologies as well, as seen in the Soviet period of Russia, or Maoist China. Yet in the United States such socialist or Marxist trends have little broad social appeal. This personality type is also most often found in fundamentalist religion, where there is some belief in an absolute truth and an authoritarian structure which extends to a God. A property of such people is a tendency to align themselves with authorities, or to bring themselves in positions of authority, and most often with respect to some ideological or belief system that is upheld as some absolute truth or certaintude by authoritarian decree.

    In the case of political conservativism, and this is largely seen in the Republican Party, there have been growing trends towards authoritarian personalities and social behavior. Eisenhower wrote a couple of letters warning of trends along these lines. In this there is a belief in the inherent and inerrant basis for the United States, economically, politically and militarily. The codification of our economic system into something quasi-religious has been an ongoing program. This is seen in the Ayn Rand trend which attempts to elevate capitalism along side physical laws as something engraved in the universe or reasoning, the Milty Friedmann idea that elevates the Bentham-Adam Smith ideology into something beyond question.

    Environmental issues and global warming bring these ideas into question, which is why the right wing is on a battle horse over this. Much the same has been replayed in the past as well, such as the GOP fought hard against the test ban treaty of 1963, for this brought to question the righteousness of American military might. On other matters of science policy the GOP has been pretty consistently wrong as well, recall Reagan and the GOP with respect to AIDS, and the same President tore down alternative energy research in the early 1980s. GW Bush gave considerable nodding support for creationism in science. There is a consistent track record of authoritarian types screwing up science, such as Lysenkoism in Soviet Russia, and China had up to the 1980 a policy of refusing research on big bang cosmology — they feared theological interpretations. Unfortunately in the United States there is considerable political pressure, and PR-media campaigns, to effectively do the same with science here.

    It is of course intellectually bad if authoritarians block research on big bang cosmology. Global warming does not IMO have nearly the fascinating implications that big bang cosmology does, but it does imply what sort of world our descendents might inherit through the rest of this century.

    Lawrence B. Crowell

  • Mike Jackson December 10, 2009, 12:24 AM

    “The conservative mentality which transitions into right winged behavior is an example of the authoritarian personality”

    The worlds worst authoritarians, at least in modern history have been “liberals transitioning into left wing behavior” as in Hitler himself (a National Socialist who leftwing historians are trying to sell as a conservative to the naive), Mao, Stalin, Castro, and on and on.

    Conservatives believe in individualism, which liberals now decry as a form of racism, being locked in to Identity Politics. Liberals believe in Big Government and yet claim to be against authoritarianism. You can’t have it both ways… unless you are the type to describe proper science as requiring the “gatekeeping” of dissenting science.

    Then it will work for you.

  • Lawrence B. Crowell December 10, 2009, 6:43 AM

    The individualism of conservatives is a sort of sick verion thereof. It is an argument by which society can be atomized further and further so people are unable to work in any organized fashion outside of corporate structures. Corporations are about as really individualistic as bee hives are — except for the elites at the top. It really is standard play with politics which trend to extremes, or a box of fools gold. It is the right winged version of the Maxrist nonsense about proletariate freedom. Two sides of the same diseased coin.

    Lawrence B. Crowell

  • Paul Eaton-Jones December 11, 2009, 3:52 AM

    What bothers me about the debate of climate change is that entrenched positions have now been established and some of the more rabid supporters from the eco-warrior brigade are seriously considering, or at least voicing, that ANYONE who dares to question the evidence, the science or research will be prosecuted under the crimes against humanity laws at The Hague. Some of the class-war warriors here in Britain have called for the death penalty when, not if, the ‘deniers’ are tried. While these numpties represent only a small minority of the establishment they are extremely vocal and have a tendency to drown out any reasoned debate. Unfortunately most of the debate is carried out by laymen, politicians and civil servants who don’t really understand the science or even the possible problem. The biggest flies in the ointment on the scientific side are the climate modellers. Their predictions change every time they run a model which leads to the news media seizing every worst-case scenario resulting in headlines such as, “5 degree rise in temperatures predicted by scientists by 2030” [The Daily Mail 2007, I think] or “0.5C rise by 2100” [same paper 2008].

  • Lawrence B. Crowell December 11, 2009, 10:31 AM

    Suppose you worked on some scientific topic and you and colleagues have established something about the physical world. Then suddenly there came a growing chorus of voices in opposition to your work because it negates the existence of the tooth fairy. There is also a lot of corporate support for this from the greeting card industry which earns billions of dollars in tooth fairy related cards and trinkets. Then further you find this is reaching the halls of government, with MPs or Senators who are opposed to it. You might find yourself a little testy over this. The little heart felt letter


    to the American physical society includes Roger Cohen, a former Manager and Strategic Planner for ExxonMobil. So you tend to go on the defensive at bit. Particularly for this subject which ultimately involves the sort of conditions we and future generation might face on the planet. I can’t defend entirely the actions of the CRU scientists, and in part because I don’t know all the details. The one thing is that the CRU can’t adulterate the date nor release it to the public because they are not proprietors of it.

    For people not marinated in ideological persiflage and aware of what is going on in the scientific community, the conclusions about this are becoming well cemented. The debate is a matter of politics and ideological purity. Particularly in the United States capitalism has been elevated to the level of quasi-religious status, or for the so called “objectivists” of the Ayn Rand variety something of equal status to Newton’s laws. The problem is that global warming is a big fly in that ointment. In the United States over the last 30 years the ideology of capitalism has been increasingly elevated to near divine status, as the nation has also been through a largely conservative or right winged period. Further, the media system in this country is compelled to produce content that is more and more outrageous, which means increasingly prurient serial content, but also news programming which has become less about facts and serious journalism and more about extremist opinion and demagoguery. This serves to elevate the endorphin levels of viewers and listeners in the form of anger, which is every bit as addictive as a drug. This increases viewership and consequently market share of advertisers. The one little problem might that American society is becoming less hinged together as it flirts with some sort of mass hysteria or psychosis. Along with this is the matter of global warming, which is a favorite whipping boy of the media — particularly the cable news outlets which serve as right winged propaganda outlets. For anyone who is not influence or “addicted” by this sort of thing and who have some understanding of what is going on these can only be seen as appalling developments.

    Lawrence B. Crowell

  • Mike Jackson December 11, 2009, 6:50 PM

    “Then suddenly there came a growing chorus of voices in opposition to your work because it negates the existence of the tooth fairy.”

    That’s a perfect example of Lawrence Crowell’s mind at work. Just perfect. And I’m sure that there are many liberal-minded scientists who are grateful for his self-abasement, not wishing to attach themselves to such a ridiculous and silly analogy.

    Alinsky would be proud of you. A scientist would be embarrassed for you.

  • Hon. Salacious B. Crumb December 11, 2009, 7:08 PM

    Ha! The jackass returnth

    Still trying to get the last word, eh?

    At least Lawrence makes sense. All you do is criticise and say nothing at all.

    Yet just another example of extremist stupidity!

  • Lawrence B. Crowell December 12, 2009, 7:00 AM

    I suppose M Jackson does have time between organizing tea parties, organizing militias and blogging elsewhere against climate legislation. This is an indication of how the American mindset is falling apart. People are losing a clear sense of things, as we see more conspiracy theories over swine flu, UFOs, 9/11 inside job conspiracies, death panels, and so forth —- and this absurd idea that thousands of scientists who work on climate science are wittingly or unwittingly a part of some grand conspiracy. This conspiracy is thought be some to be a grand scheme to smash out capitalism and raise the red flag of communism around the world. I know someone who thinks just this! Yet this crap works, and it gets people’s endorphin levels up as their anger addiction is stroked.

    In the end the human race just might be 6.8 billion ground apes exponentially rampaging out of control. The more I hear these right wingnuts prate on the more it appears we are little more than a great bio-dysfunction.

    If nothing else the United States is at best going to become a crone of a nation populated by cranky conservative curmudgeons.


  • Lawrence B. Crowell December 12, 2009, 7:49 AM

    This is from Robert Parks of the American Physical Society.

    WHAT’S NEW Robert L. Park Friday, 11 Dec 09 Washington, DC

    At the Copenhagen climate talks, Michel Jarraud, secretary general of the
    international weather agency, told a news conference that the period from
    2000 through 2009 will almost certainly be the warmest decade in the 150
    years of modern record-keeping. And with just a few weeks remaining, 2009
    will likely be the fifth warmest year on record. But what about those
    hacked emails from the climate research unit at the University of East
    Anglia? Jarraud replied that there is no evidence that independent
    estimates showing a warming world are in doubt. The more interesting
    question is who was behind the break-in and why? The use of dirty tricks to
    cast doubt on the reality of global warming began with Kyoto.

    It?s awkward that the United States, alone among major nations, declined to
    ratify the Kyoto protocol calling for reduction of greenhouse gases.
    Without the United States, which is responsible for 1/3 of the world’s
    greenhouse emissions, the Kyoto accord was meaningless. To convince
    Congress and the public that scientists have serious doubts about global
    warming, a petition was launched. The only return address on a massive
    mailing to academic scientists was a P.O. Box. The only name was Fred
    Seitz. A famous condensed matter physicist in his earlier years, Seitz
    headed the ultra-conservative George C. Marshall Institute in Washington.
    Seitz was also a permanent paid consultant of the R.J. Reynolds Tobacco
    Company. Although he conducted no tobacco research, Seitz used his
    scientific reputation to cast doubt on medical evidence showing that
    secondhand smoke is dangerous. Now he was doing the same for global
    warming. The petition mailing included a Wall Street Journal op-ed that
    said we have an ethical responsibility to burn as much fossil fuel as
    possible to get carbon out of the ground and into the air where it can
    create life. According to NBC news correspondent Ian Williams this week,
    the life C02 is helping to create in Malaysia includes the Aedes Aegypti
    mosquito that multiplies more rapidly as the temperature rises. Aedes
    transmits dengue fever.

  • Paul Eaton-Jones December 14, 2009, 3:23 AM

    To Lawrence Crowell @10:31 a.m11-12-09. Very good analysis of the mind-set in America [as we see it over here]. It is also coming to represent a growing body of opinion in government and amongst the movers & shakers in the economy etc. While I feel capitalism is generally ‘good thing’ the way it has become the new religion with all the baggage that entails is a very disturbing move as the past two years has shown only too clearly.