A Simple Pedagogical Model Linking Initial-Value Reliability with Trustworthiness in the Forced Climate Response

Although the development of seamless prediction systems is becoming increasingly common, there is still confusion regarding the relevance of information from initial-value forecasts for assessing the trustworthiness of the climate system's response to forcing. A simple system that mimics the real climate system through its regime structure is used to illustrate this potential relevance. The more complex version of this model defines "reality" and a simplified version of the system represents the "model." The model's response to forcing is profoundly incorrect. However, the untrustworthiness of the model's response to forcing can be deduced from the model's initial-value unreliability. The nonlinearity of the system is crucial in accounting for this result.