Here is a quote from Popper on the problem of induction and the importance of systematic attempts to falsify hypothesis and theories:
” it becomes possible to resolve in a simple way the contradiction which constitutes the problem of induction. We can, quite consistently, interpret natural laws or theories as genuine statements which are partially decidable, i.e. which are, for logical reasons, not verifiable but, in an asymmetrical way, falsifiable only: they are statements which are tested by being submitted to systematic attempts to falsify them.”
Ref.: “The logic of scientific discovery; Page 314”
In the contribution from working group I to the fifth assessment by IPCC there are no sign of such a methodical approach. In the assessment of 1535 pages:
The word falsify is used just once .
The word falsified in not ever used.
How can you possibly submit hypothesis and theories to systematic attempts to falsify them without ever using the the words falsify or falsified.
What is written in the report however is phrases like:
“The IPCC process is aimed at assessing the literature as it stands and attempts to reflect the level of reasonable scientific consensus as well as disagreement.”
“In the course of the IPCC assessment procedure, chapter teams review the published research literature, document the findings (including uncertainties), assess the scientific merit of this information, identify the key findings, and attempt to express an appropriate measure of the uncertainty that accompanies these findings using a shared guidance procedure.”
“The degree of certainty in key findings in this assessment is based on the author teams’ evaluations of underlying scientific understanding and is expressed as a qualitative level of confidence (from very low to very high) and, when possible, probabilistically with a quantified likelihood (from exceptionally unlikely to virtually certain). Confidence in the validity of a finding is based on the type, amount, quality, and consistency of evidence (e.g., data, mechanistic understanding, theory, models, expert judgment) and the degree of agreement. Probabilistic estimates of quantified measures of uncertainty in a finding are based on statistical analysis of observations or model results, or both, and expert judgment. Where appropriate, findings are also formulated as statements of fact without using uncertainty qualifiers.”
Here is another quote from Popper on the practice of expressing degrees of reliability:
“All this glaringly contradicts the programme of expressing, in terms of a ‘probability of hypotheses’, the degree of reliability which we have to ascribe to a hypothesis in view of supporting or undermining evidence.”
Ref: “The logic of scientific discovery; Page 314”
IPPC seems to be ignorant of the empirical method and the works by Karl Popper.
Hence IPCC seems to be ignorant of modern scientific theory.
The contribution from working group I to the fifth assessment by IPCC looks like a huge monument over inductivism.