Climate Change: A Very Short Introduction

by Mark Maslin

In the most recent IPCC AR6, the past- and future-emission scenarios were used in about 100 distinct, independent GCMs. Each of these models has its own independent design and parameterizations of key processes. The independence of each model is important, as confidence may be derived from multiple runs on different models providing similar future climate predictions. In addition, the differences between the models can help us to learn about their individual limitations and advantages. Within the IPCC, due to political expediency, each model and its output is assumed to be equally valid. This is despite the fact that some are known to perform better than others when tested against the reality provided by the historical and palaeoclimate records. Moreover, though we understand uncertainty within a single model, the notion of quantifying uncertainty from many models currently lacks any real theoretical background or basis.