Why the climate panic?

Daily we are told that we are wicked to burn fossil fuels.  The carbon dioxide which is inevitably emitted accumulates in the atmosphere and the result is "climate change." If the stories are to believed, large areas of the world will become uninhabitable, either through drought or flood. Crops will wither, rivers will dry up, polar bears will disappear and malaria will become rampant.

You know, it is a big "IF". We could waste zillions for nothing.  Indeed, a zealot called Lord Stern has estimated that it would be worth spending a few trillion dollars each year to avoid a possible disaster in 200 years' time. Because he is associated with the London School of Economics he is believed - by those whose experience of insurance is limited. It is not worth insuring against something that might happen in 200 years time - we will all be dead and beyond caring.

So I decided to examine the hypothesis from first principles. 

1. There are five steps to the hypothesis:The observation that the carbon dioxide (CO₂) content of the atmosphere is rising. 
2. The observation that the rise in CO₂ in the atmosphere is largely paralleled by the increase in fossil fuel combustion. Combustion of fossil fuels clearly results in emission of CO₂, so it is eminently reasonable to link the two increases. 
3. The observation that CO₂ can scatter infra-red over wavelengths primarily at about 15 µm.  Infra-red of that wavelength, which should be carrying energy away from the planet, is scattered back into the lower troposphere, where the added energy input should cause an increase in the temperature. A photon of about 15µm wavelength absorbed by a CO₂ molecule is almost instantaneously re-emitted in a different direction with a slight loss of energy. The CO₂ molecule gains a very small amount of energy in the process, insufficient to raise its temperature significantly. This explanation is somewhat simplistic, because the whole of the troposphere is radiating, and because the temperature drops with altitude, at about 10^oC/km for dry air and 6^oC/km for moist air. The height of thermal equilibrium is about 5km above sea level, which is why the surface is about 6x5 = 30^oC warmer than it would have been if there were no greenhouse effect. 
4.  The expected increase in the energy of the lower troposphere may cause long-term changes in the climate and thermosphere, which will be characterized by increasing frequency and/or magnitude of extreme weather events, an increase in sea temperatures and a reduction in ice cover.
5. These phenomena may make areas of the globe uninhabitable either through extreme drought or flooding in the worst cases, but perhaps more subtly through impacts on the biosphere as a whole to which mankind is unable to adapt.

 Thus in this first post I look at the observations of the carbon dioxide (CO₂) content of the atmosphere; in four subsequent ones I will examine each of the other steps.

The observations of the increase in CO₂ in the atmosphere are incontrovertible. There has been continuous observation from the Mauna Loa observatory since 1958:

 The annual rise and fall is due to deciduous plants growing or resting, depending on the season.  But it is clear that the long-term trend is ever increasing levels of CO2 in the atmosphere.

Before 1958, there were only sporadic measurements of CO2. Nevertheless they give a clear indication that there was minimal change in the atmosphere before about 1850:

 

There was a slight surge in atmospheric levels from about 1910, then a period of near stasis until after 1950, when there was a strong and ongoing increase which has continued to this day.

Remember this pattern - it will re-appear in a different guise in our next post.