Saturday, January 21, 2012

Could CFC's be the real problem?

In my last note, I made a ghastly error. I called a little peak at around 9-10 microns a CO2 peak when it is really an ozone peak. Humble grovellings to all who pointed out my mistake!

However, it led me to a fascinating paper by Quin-Bin Lu, Department of Physics and Astronomy , University of Waterloo, Waterloo, Ontario, Canada

He confirms what I have long believed, that the carbon dioxide bands are already essentially saturated. Therefore CO2 CAN NO LONGER CONTRIBUTE TO GLOBAL WARMING. It has done its job - all the greenhousing it can do is done, over, finished.

More importantly, that little 9-10 micron peak is not just ozone, but also CFC's. Lu has an interesting graph showing virtually no correlation between CO2 and measured temperature changes, but an even more interesting one showing an excellent correlation between CFC's and the temperature changes:

That is a good enough correlation for me to think there is something VERY INTERESTING here. Watch this space!

Being a climate skeptic is FUN!

Sunday, January 8, 2012

There has been a great debate during the past week on the What’s Up With That blog, about a new global warming theory. I no longer believe the new theory to be valid, but taking part in the debate had the advantage that it clarified for me some of the issues.

If you consider this as a standard problem in heat transfer, at equilibrium the outgoing energy must balance the incoming energy. We know how much radiant energy the sun inputs, and we seem to agree on its fate – X reflected into space, Y adsorbed by the globe. So the question is how does Y (plus any input from geothermal and man-made energy) leave the globe? Ultimately it can only leave by radiation, because convection and conduction can play no part in space. And indeed, viewed from space we can see all the atmospheric absorbers playing their part, just as we wondered about the sun’s spectrum a century or so ago.

Interestingly, the only gases that play a role in our radiation budget are those that are active in the infrared, which are known as the greenhouse gases. Oxygen, nitrogen, argon and other monatomic and symmetrical diatomic gases in the atmosphere are to all intents and purposes totally transparent to the outgoing radiation. But the greenhouse gases play a role in both incoming and outgoing radiation. They heat the atmosphere by adsorbing ultraviolet from the incoming radiation, classically in the case of ozone, which undergoes photolysis with photons of less than 330nm to produce an oxygen molecule and an active oxygen atom. Nitrous oxide also absorbs strongly in the ultraviolet, but only photolyses with photons of 240nm and less, which is one reason why it is relatively long-lived in the atmosphere. Carbon dioxide and water do not absorb ultraviolet significantly at wavelengths in the atmosphere, so play no part in warming the atmosphere by uv absorption.

Greenhouse gases absorb relatively short wavelength infrared and re-emit slightly longer wavelength infrared from both incoming and outgoing radiation. They therefore heat the atmosphere by absorbing the incoming radiation and so reduce the energy available at the surface.

However, when the surface re-radiates, the greenhouse gases absorb the outgoing short wavelength infrared, which also heats the atmosphere. It is an interesting question whether the reduction in energy reaching the surface from incoming sunlight is greater than the energy trapped by absorption from the outgoing radiation. But key is the fact that the greenhouse gases warm the atmosphere by an estimated ~33 deg K. The more greenhouse gases there are, the greater the energy they contribute (whence the concern about global warming).

We know this from looking at the spectra. The figures below show the spectra over the Arctic – chosen because there is much less water vapour in the way, and because water vapour is such a strong absorber, it dominates the same spectrum over the tropics. In the upper curve, we are looking down at Earth, and can see that the outgoing radiation is characterized by:

1. The Arctic is basically radiating at about 268oK

2. There is an absorption ‘bite’ at around 15 µm due to both H2O and CO2

3. There is a further ‘bite’ at around 9-10 µm due to CO2

4. There is a big ‘bite’ at less than 8 µm due to H2O

In the lower curve, looking up at night, we see:

  • Most of the adsorbed 15 µm energy is re-emitted and returned to the surface.
  • From about 12 to 8 µm there is no returned energy – it has all escaped to space except a little of the energy adsorbed and re-emitted by CO2 at 9-10 µm.
  • From about 8 µm most of the energy absorbed by H2O from the outgoing radiation is returned.

Thus, when the surface radiates, the greenhouse gases absorb the outgoing short wavelength infrared, which also heats the atmosphere. Note that the only real contribution from CO2 is that little bit between 9-10 µm.

The energy deposited in the atmosphere is distributed primarily by convection. Convection is driven by a) surface heating and cooling and b) evaporation of water (moist air is lighter than dry air). As the air rises, it cools and the point is reached where it is cold enough for the water vapour to condense, which releases latent heat. At about 12km above the surface, the pressure reaches about 10kPa and water vapour no longer plays a significant role. Instead, heating of the atmosphere takes over, and the temperature rises with altitude. Mixing is dramatically reduced, because convection is no longer possible. The region where this change occurs is called the tropopause and the region above the tropopause is the stratosphere. The tropopause is not a particular point, but a region extending from about 10km to about 18km over which the transition from troposphere to stratosphere takes place.

Nevertheless, if you integrate the energy that is finally lost to space, you discover that we radiate primarily through the 12 – 8 µm ‘window’. There is some contribution from the ‘grey window’ at greater than 16 µm, but it is relatively small (around 5% but varies with latitude)