In addition, for sea-level rise there are two “low confidence” scenarios. In order of increasing CO2 and other greenhouse gas emissions, and thus in order of increasing theoretical temperature rise, they are called the “1.9”, “2.6”, “4.5”, “7.0”, and “8.5” scenarios. The UN IPCC uses five different scenarios. That’s why Boeing and Airbus use wind tunnels to test physical scale models of proposed airplanes whose design is based on computer model outputs … because model outputs aren’t evidence.Īnd what do the UN IPCC models and the “expert judgment” tell us about the future sea-level rise in San Francisco? It depends on the “Scenario”. As a man who has programmed computer models of a host of systems, I can assure you that model output is “evidence” only in the very simplest of systems. “Evidence”, for them, also includes models and expert judgment. First, “evidence” in their world is not just data, observations, and mechanistic and theoretical understanding.
(2) Likelihood provides a quantified measure of confidence in a finding expressed probabilistically (e.g., based on statistical analysis of observations or model results, or both, and expert judgement by the author team or from a formal quantitative survey of expert views, or both.Ī few notes on this quote. (1) Confidence is a qualitative measure of the validity of a finding, based on the type, amount, quality and consistency of evidence (e.g., data, mechanistic understanding, theory, models, expert judgment) and the degree of agreement and Two calibrated approaches are used to communicate the degree of certainty in key findings, which are based on author teams’ evaluations of underlying scientific understanding: Throughout this Technical Summary, key assessment findings are reported using the IPCC calibrated uncertainty language (Chapter 1, Box 1.1).