Mysterious Models and Enigmatic Ensembles
Reto Knutti (ETH Zurich, Institute for Atmospheric and Climate Science)
Abstract: As our understanding improves, more observations become avail – able, and computational capacity increases, climate models continue to in – crease in complexity to synthesize all that knowledge. The hope is that as more and more processes are considered at greater realism and higher resolution, the models will converge to reality. But do they really, how do we know, and indeed should they? What is the purpose of current global climate models? Are they built to understand processes, to quantify past changes, or to predict the future, and do all of those require the same models? Uncertainty in climate projections is difficult to quantify, and has not decreased significantly in the past few years, partly as a result of irreducible climate variability. Progress in model evaluation as well as statistical methods to interpret and combine model projections is urgently needed, in particular as more models of different quality and higher complexity, including perturbed physics ensembles and ensembles with structurally different models become available.