In your editorial, "Denialism is not an option" (December 4), you say that "the point here is not to say which side is right, or that either side is all right or all wrong".
I would suggest that the point is very much "which side is right". If the proponents of human-induced climate change are correct, we may be persuaded to invest an enormous 2% of global GDP, and possibly even 5%, to prevent it. We may be persuaded to condemn many in the developing world to continued poverty for the greater good.
But what if the denialists are correct? There is significant evidence to indicate that whatever changes there may be in the climate are a result of natural cycles that have been going on for millennia.
The "evidence" of human-induced climate change appears to me to be computer models whose assumptions are that all changes are due to CO, factoring out natural climactic cycles, sunspot activity, and so forth, and which are nowhere near sophisticated enough to model things like clouds and other heat-retaining and distributing mechanisms.
Despite the efforts of the University of East Anglia's Climatic Research Unit and the UN's Intergovernmental Panel on Climate Change (IPCC) to downplay it, the world was warmer in the Medieval Warm Period from 900-1 300 AD, when vines were grown in England and Greenland was green. This was followed by the Little Ice Age, from 1 400 to 1 850 AD, when the world was much colder than today. It is also interesting that the fastest rate of increase in the world's temperature in the 20th century was in the first 30 years, before anyone could argue a COČ connection.
COČ is, after all, only a minor trace gas, making up less than 0,04% of the atmosphere. Water vapour at 3% is a far more important greenhouse gas, but the complex and dynamic relationship between clouds and their warmth-reflective and retention effects is extremely difficult to model. There may be more plausible scientific theories to explain climatic cycles than increases in COČ levels, like cycles of sunspot activity. Greater sunspot activity reduces the cosmic rays hitting the earth, thus reducing cloud formation and leading to increased surface temperatures.
Finally, the climate record of the past 11 years has shown level or falling temperatures. This lack of warming was not predicted by any of the models used by the IPCC.
Denialism is an option and the points that denialists make deserve to be taken seriously, rather than dismissed out of hand.
Ranking the Analysts 2009
