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.
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.