Watt about the Magellan telescope?

Watts Up With That (WUWT) has a recent post called new telescope brings the power of Hubble down to Earth. It’s really a press release from the University of Arizona about recent results using the new MagAO system on the 6.5m Magellan Telescope located in Chile. It’s an interesting article and it’s nice to see such things promoted on WUWT.

What I find a little ironic, whenever an astronomy article like this appears on WUWT, is that noone seems to mention how atmospheric water vapour and CO2 influence astronomical observations (although, in fairness, the WUWT post is about an optical observatory, so it’s not necessarily that relevant in this case). Astronomical observations are normally done in a range of different wavelength bands. Typical examples are U, B, V, I, J, H, and K bands. U is essentially ultraviolet, B is the blue part of the visible band, V is the main part of the visible, and I, J, H, and K are all infrared bands. The interesting thing about the I, J, H and K bands is that their wavelengths ranges were specifically chosen to match what are called atmospheric windows.

Just as water vapour and CO2 (and other greenhouse gases) absorb outgoing infrared radiation, they also absorb incoming infrared radiation. The I, J, H, K, and other infrared wavelength bands are then chosen to be in the wavelength ranges where this absorption is minimised. This is illustrated in the figure below, which I took from the Cool Cosmos webpage. In fact, in the infrared very little, or no, flux can actually reach the ground, which is one reason why telescopes are located at high altitudes. The highest ground-based observatories (those on Hawaii and in Chile are above 4000m) are above almost all the atmospheric water vapour. It’s also interesting that most space-based infrared observatories use the same wavelength bands as ground-based observatories, despite these being chosen to match the atmospheric windows.

Illustration showing the regions of the electromagnetic spectrum where the atmosphere is transparent (credit : Cool Cosmos, Caltech).

Illustration showing the regions of the electromagnetic spectrum where the atmosphere is transparent (credit : Cool Cosmos, Caltech).


So, I think it’s great that Anthony puts up these kinds of posts. It’s interesting science and is generally well received. I just think it’s a little ironic that most appear not to realise that the very physics/science that underpins our understanding of global warming also plays a crucial role in other areas like astronomy. I don’t really know the history of science particularly well, but I suspect that a great deal of our understanding of absorption and emission lines came from astronomy or from research driven by astronomy. Admittedly those at WUWT don’t actually deny the greenhouse effect, but they do rather underplay its significance.

To be honest, I don’t really know why I wrote this post. It’s kind of nice to say something somewhat positive about a WUWT post, and it just reminded me that the fundamentals of climate science are no different to the fundamentals underpinning many other (if not all) science areas. That’s why it would be quite remarkable if our basic understanding of global warming and climate change turns out to be wrong in any particularly significant way.

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17 Responses to Watt about the Magellan telescope?

  1. Latimer Alder says:

    Yep. Astronomy was a powerful mover in spectroscopy. As was chemistry.

    Here’s an account of the discovery of helium – with important contributions from both

    http://www.universetoday.com/53563/who-discovered-helium/

  2. Rob Honeycutt says:

    I would venture to guess that at least half of Anthony’s audience actually does reject even the most fundamental radiative physics of CO2. But Anthony and that half of his audience tolerate each other because they are like-minded politically.

  3. Steve Bloom says:

    IIRC the relevant initial work on IR was done by the USAF for use in missile sensors.

  4. Yes, that may well be true and it’s ringing a bit of a bell. I think I have heard something along those line before.

  5. Indeed, the history of the discovery of helium is very interesting but, as I mention in the post, my knowledge of the history of science is somewhat limited 🙂 Thanks for the link.

  6. That is certainly my impression, although – as far as I can tell – they’re discouraged from actually stating this too openly.

  7. Flakmeister says:

    Does Tony WIllard does realize that the “sexy” astronomy is in the IR region?
    Does he?
    Feel free to ignore the rhetorical question….

  8. Hmmm, I wonder if Anthony could actually cope with this. It might just be too much for him 🙂

  9. The same science that went into heat seeking sensors for missiles and IR sensors on satellites and telescopes also validates human warming. If you support and understand one branch of the science, denying or muddying another is both blind and hypocritical.

    At some point, Watts will have this epiphany on global warming. At that point, he will shift to luke-warmism and pretend that this view was always the view he supported. When this happens will depend on the level of social and political pressure leveled against climate change deniers and how visible the ongoing harm from climate change becomes. It’s just a simple and shameful aspect of the frankly wrong-headed and immoral position he’s taken on global warming for such a long period.

  10. Tom Curtis says:

    It turns out that infrared radiation was indeed discovered by an astronomer, William Herschel. The initial exploration into the absorption of IR by gases, however, was done by the physicist, John Tyndale. As has already been noted by Steve Bloom, the detailed IR spectroscopy of atmospheric gases was primarily done by the USAF as part of its efforts to develop effective IR homing missiles.

  11. Tom Curtis says:

    robert, I believe Watts is already technically a luke-warmer. That is, he believes that enhanced CO2 causes some, small increase in surface temperature. His estimate of that increase is likely to be in the range of 0-1.5 C per doubling of CO2, and most likely in the range 0.5-1 C. I think he also thinks that humans are the probable cause of the increase of CO2. Despite this, he frequently publishes articles that would contradict that belief due to simple scientific incompetence. He does not realize he is contradicting himself. He bases his views not on his understanding of the science, but on what Lindzen, Spencer and Pielke Snr have told him to be views that can be rationally maintained.

  12. Especially for the Hubble telescope!

  13. 3 C per doubling CO2 is a difficult sensitivity to defend when you look at paleoclimate (Pliocene at 2-3 C warmer and 360 to 405 ppm, 5 C of warming with a 100 ppm CO2 increase and .5 Watt/meter squared orbital forcing at the end of the last ice age, and 5-6 C warming at 500-600 ppm CO2 40-50 million years ago).

    It seems to me that Watts cynically defends the most conservative position possible. And the new fight is shaping up over climate sensitivity (It’s going to warm a little, but it’s no big deal..). The consensus science is probably too conservative and the ultra conservative radicals are setting up to push the science more radically in that direction (to manipulate the science to officially affirm a lower sensitivity). In this, we are, once again setting ourselves up for very bad surprises.

    Excuse the vitriol, but people like Watts make me want to yack. They’re stuffing the science full of as much reticence as possible.

  14. Tapani L. says:

    I’m not an expert of climate science history, but I’ve read some and I read the Arrhenius landmark paper from 1896 a few times when I wrote a blog post or two about it in Finnish. Arrhenius based his estimates of atmospheric IR absorption on astronomer Samuel Langley’s series of rudimentary spectroscopic infrared measurements of the full Moon (Langley wanted to measure the temperature of the Moon) in different conditions and at different heights from the horizon – e.g. if the Moon is at 30 degrees from the horizon, the IR radiation from the Moon goes through twice the atmosphere and thus twice the CO2 and water vapor compared to the Moon at zenith. The measurements weren’t too good, but Arrhenius was pretty sure he did away with systematic errors and the Moon’s surface temperature is close enough to the Earth to get reasonable answers. He knew about water vapor feedback, could separate the effects of CO2 and water vapor and got roughly the same sort of answers for climate sensitivity as we have today.

    The ingeniousness baffles me. He even goes on to quote in length a Swedish geologist colleague of his who had calculated that the coal usage of 1890s made more CO2 emissions than volcanic eruptions, which is true. There were good thoughts on the carbon cycle, the possibility of anthropogenic warming from accumulating CO2, and so on. But the main point was to explain ice ages and the mechanism behind them.

  15. Very interesting, thanks.

  16. Pingback: Astronomy is the science dealing with all the celestial objects in the universe

  17. Pingback: Astronomy | alan's Blog!

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