ACCORDING to the philosopher Thomas Kuhn, a scientific theory, for example, Anthropogenic Global Warming (AGW) is likely to be based on a particular set of experimental and theoretical techniques for matching it with what is observed in the physical world.
The hard core of AGW theory is embodied in the law and mathematical expression described by Swedish scientist Svante Arrhenius over one hundred years ago. In its original form, Arrhenius’ law states that if the quantity of carbonic acid increases in geometric progression, the augmentation of the temperature will increase nearly in arithmetic progression. Dr Arrhenius calculated values for the absorption of infrared radiation by atmospheric carbon dioxide and speculate that a doubling of atmospheric carbon dioxide would cause a global temperature rise of 5 – 6 °C.
It wasn’t until 1988 that AGW captured significant political attention. That was when climatologist James Hansen, in his testimony to US congressional committees, claimed a 4.2°C global temperature increase would result from a doubling of atmospheric carbon dioxide.
Since then estimates have been continuously adjusted down.
In the 1995 IPCC report, for example, a doubling of carbon dioxide was predicted to cause a 3.8 °C increase and then in 2001 a 3.5°C increase and in 2007 a 3.26°C increase.
In 2008, twenty years after his initial influential testimony, Professor Hansen issued a statement to the effect that his central estimate of lambda was now 0.75, requiring a further reduction of the official climate sensitivity estimate by one quarter, to 2.5°C degrees for a doubling of carbon dioxide.
Even leading skeptical scientists Richard Lindzen and Roy Spencer agree to a reduced sensitivity for a doubling of carbon dioxide.
Do all these adjustments indicate a problem with the hard core of AGW theory?
The late mathematician and philosopher Imre Lakatos claims that scientists who subscribe to a particular scientific theory, also known as a paradigm, will tend to work to ensure its hard core is unfalsifiable.
This post builds on, and synthesizes, many of the comments provided by readers at: The Need for a new Theory of Climate (Part 1). The Need for a New Theory of Climate (Part 1)