William of Occam (1285-1347) was an English Franciscan monk and philosopher to whom is attributed the saying ‘Pluralitas non est ponenda sine necessitate’, which translates as ‘Plurality should not be posited without necessity.’ This is a succinct statement of the principle of simplicity, or parsimony, that was first developed by Aristotle and which has today come to underlie all scientific endeavour.
The phrase ‘Occam’s Razor’ is now generally used as shorthand to represent the fundamental scientific assumption of simplicity. To explain any given set of observations of the natural world, scientific method proceeds by erecting, first, the simplest possible explanation (hypothesis) that can explain the known facts.
This simple explanation, termed the null hypothesis, then becomes the assumed interpretation until additional facts emerge that require modification of the initial hypothesis, or perhaps even invalidate it altogether.
Given the great natural variability exhibited by climate records, and the failure to date to compartmentalize or identify a human signal within them, the proper null hypothesis – because it is the simplest consistent with the known facts – is that global climate changes are presumed to be natural, unless and until specific evidence is forthcoming for human causation.
It is one of the more extraordinary facts about the IPCC that the research studies it favours mostly proceed using an (unjustified) inversion of the null hypothesis – namely that global climate changes are presumed to be due to human-related carbon dioxide emissions, unless and until specific evidence indicates otherwise.
Why would scientists essentially pervert science itself by ignoring these basic tenets of science? Why would they seek human causation for global climate change, when the simplest answer -- that weather changes because we live in a dynamic, and not static, natural world -- remains plausible and persuasive?
The answer is also subject to Occam's Razor. Why do people take irrational positions and hold them despite new evidence (such as the fact that there has been no measurable warming over the past 15 years)?
Hate. Leftists hate capitalism, they hate industry, they hate machinery, they hate cars and roads, they hate suburbia, they hate SUVs, they hate mean rich people. Hate and fear... they are Luddites, afraid of change, longing for an Edenic world.
And, make no mistake, Greens are camouflaged Reds, and always have been.