onsdag 7 oktober 2009

Short-Time vs Long-Time Accuracy 2

The question of short-time vs long-time accuracy of climate models plays an important role in the debate on climate change.

Roger Pielke Sr. takes a critical look the recent article by Ed Hawkins and Rowan Sutton, 2009: The Potential to Narrow Uncertainty in Regional Climate Predictions. Bulletin of the American Meteorological Society. DOI: 10.1175/2009BAMS2607.1. 1095–1107.

Pielke questions the claim illustrated in the above figure of the article, that modeling errors decrease with increasing time. We posed a similar question in the blog post Short-Time Accuracy vs Long-Time Accuracy.

We noticed that a good deal of happy cancellation must be present in order for modeling errors to decrease with time. It is doubtful if this is the case in a complex dynamical system like the global climate. This means that if climate models are not short-time accurate, they have a small chance to be long-time mean-value accurate. If this is true then, the accuracy of climate models can be tested on short-time predictions, which can be checked in short-time, say 2 years.

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