Many researchers have theoretically quantified the ‘Direct’ effect on the augmentation of the total Greenhouse effect by increased atmospheric levels (particularly carbon dioxide). These efforts include, for example Wenyi Zhong and Joanna Haigh’s 2013 paper "The greenhouse effect and carbon dioxide".
Any proper scientific approach (approved by Karl Popper, the 20th century philosopher of science) would be to start out with a null hypothesis.
However, all the studies used to verify the assertion ‘Anthropogenic emissions cause Global Warming’ start out by assuming the assertion is true.
This means they axiomatically include the required outcome in their calculations. In the words of Thomas Sowell 'they are based on a flawed, utopian vision rather than empirical evidence and practical consequences'.
This is an example of circular reasoning and confirmation bias research. This is deeply unscientific and undermines the verifying calculations so as to relegate them to the realms of pseudo-science.
This groupthink approach leads most non-scientists and many Climate Change believers in the scientific community to mistakenly consider the asserted ‘fact’ as being verified by application of the scientific method. The detailed 'Direct' effect calculation uses the HITRAN spectral database and is more fully described in 'Natural and Anthropogenic Climate Change - Volume Two'.
Although these calculations are fundamentally unscientific, they do not predict as much Greenhouse effect enhancement as the modellers require to be able to predict ‘Climate Apocalypse’. These calculations are, therefore, sometimes termed the 'Direct Effect'.
Therefore, another mechanism must be invoked.
This mechanism is termed ‘sensitivity’ or, sometimes, ‘feedbacks’.
Sensitivity is asserted to work (apparently uniquely) on CO2 ‘Direct’ warming and multiplies the ‘Direct’ effect by a factor of between two and four. It appears not apply to any of the many natural warming factors. The Climate Change belief mandates all warming (or almost all) as anthropogenically caused.
The mechanism for ‘Sensitivity’ is purported to involve water (vapour and clouds) but no satisfactory mechanism can be offered. This pushes the whole ‘Sensitivity’ concept into the realms of pseudo-science alongside the theoretical ‘Direct effect’ calculation.
The Cardinal Model (described elsewhere on this website) adopts a more rigorous scientific approach that would be approved of by Karl Popper.
It does not start off at the required finishing line and therefore does not employ circular logic as proof.
It rather investigates what can be observed. Observed Greenhouse effect variations can by linked to atmospheric Greenhouse gas concentration variations through the well-known analysis technique of empirical parameter modelling.
The clear conclusion of the Cardinal Model is that carbon dioxide minimally contributes – less than 0.1⁰C to from pre-industrial times to 2025 or, indeed, to the point at which CO2 doubles (i.e. to 554ppm).
This is in stark contrast to the Anointed view that doubling CO2 will lead to between 2.6⁰C and 4⁰C warming.