Previous Chapter: 2 - An introduction to the Greenhouse effect
The IPCC Model is built on a core assertion that shapes every part of its structure: Anthropogenic emissions cause global warming. This assumption is not tested by the model; it is embedded within it. As a result, the model does not investigate whether human emissions drive warming, but rather begins by assuming that they do.
This creates a fundamental limitation: the IPCC Model is not a hypothesis to be tested but a framework constructed to reinforce its own starting premise. Key quantities such as radiative forcing are defined such that increases in greenhouse gases necessarily produce warming. By defining causation at the outset, the model becomes circular: its conclusion is guaranteed by its structure.
The model treats the pre-industrial atmosphere as a stable baseline and attributes all subsequent warming to human activity. Natural climate variability is treated as noise, not as a genuine driver. This sharply contrasts with the scientific method, which requires that natural variability be considered the default explanation until evidence confidently demonstrates otherwise.
At the heart of the IPCC approach is the concept of forcing, defined as the change in net radiation caused by changes in atmospheric composition. The model calculates that increases in greenhouse gases such as CO2 lead to an increase in forcing, which in turn must lead to warming. The size of this warming is amplified by an assumed climate sensitivity multiplier, intended to represent positive feedbacks from water vapour and other processes.
However, these amplifications are not measured values; they are assumptions layered on top of assumptions. As a result, small uncertainties in the base calculation compound into large uncertainties in projected temperature rises. Despite this, the model generates projections used to justify aggressive climate policies and international action.
When compared with observed data, particularly the satellite-derived greenhouse-effect record from 1985 to 2022, the model performs poorly. It fails to match the magnitude, pattern, and variability of real-world measurements. In some periods, such as 1998 to 2008, the IPCC model predicts warming while observed temperatures fall. This mismatch between model output and actual behaviour indicates that the underlying assumptions are insufficient to describe the greenhouse effect accurately.
Because the IPCC Model begins with a predetermined conclusion and treats its own assumption as evidence, it cannot be scientifically validated. A model that cannot fail cannot be tested. This is the fundamental distinction between science and affirmation. As a result, the IPCC Model cannot be considered a reliable predictor of future climate behaviour, nor a solid foundation for the policy burdens built upon it.
Next Chapter: 4 - The TRANS Model – Summarised: Construction and Outcomes