Very Important New Paper “A Comparison Of Local And Aggregated Climate Model Outputs With Observed Data” By Anagnostopoulos Et Al 2010

There is a very important new paper which has compared climate model results with observations. It is

Anagnostopoulos, G. G., Koutsoyiannis, D., Christofides, A., Efstratiadis, A. & Mamassis, N. (2010) A comparison of local and aggregated climate model outputs with observed data. Hydrol. Sci. J. 55(7), 1094–1110.

The abstract reads

We compare the output of various climate models to temperature and precipitation observations at 55 points around the globe.We also spatially aggregate model output and observations over the contiguous USA using data from 70 stations, and we perform comparison at several temporal scales, including a climatic (30-year) scale. Besides confirming the findings of a previous assessment study that model projections at point scale are poor, results show that the spatially integrated projections are also poor.

The paper is examining the claim presented in the introduction of the paper that

According to the Intergovernmental Panel on Climate Change (IPCC), global circulation models (GCM) are able to “reproduce features of the past climates and climate changes” (Randall et al., 2007, p. 601).

What the authors of the Anagnostopoulos et al. (2010) paper have found is that [highlight added]

It is claimed that GCMs provide credible quantitative estimates of future climate change, particularly at continental scales and above. Examining the local performance of the models at 55 points, we found that local projections do not correlate well with observed measurements. Furthermore, we found that the correlation at a large spatial scale, i.e. the contiguous USA, is worse than at the local scale.

There is discussion of this paper in two accompanying articles.

The first paper is a comment on the Anagnostopoulos et al. (2010) paper. It is

 Wilby, R. L. (2010) Evaluating climate model outputs for hydrological applications – Opinion. Hydrol. Sci. J. 55(7), 1090–1093.

Wilby (2010) should be read also in its entirety, One excerpt, for example, reads

“Even if we could build perfect climate models, uncertainty about future economic and demographic pathways, natural forcings by solar and volcanic activity, and a host of non climatic pressures, mean that regional hydrological projections would still be highlyuncertain. In other words, characterizing uncertainty through concerted scientific action may be a tractable proposition, but there appears to be no immediate prospect of reducing uncertainty in the risk information supplied to decision makers.”

The second article is an editorial from the Editor of the journal

Kundzewicz, Z. W., and E.Z. Stakhiv (2010) Are climate models “ready for prime time” in water resources managementapplications, or is more research needed? Editorial. Hydrol. Sci. J. 55(7), 1085–1089.

In this article, in which they summarize the perspective of the Anagnostopoulos et al. (2010) and Wilby (2010) papers,  they include the excerpts from the text [highlight added]

Simply put, the current suite of climate models were not developed to provide the level of accuracy required for adaptation-type analysis. They were designed to provide a broad assessment of the response of the global climate system to greenhouse gas (GHG) forcings, and to serve as the basis for devising a set of GHG emissions policies to slow down the rate of growth of GHGs, and, by this, to mitigate global warming impacts. To expect more from these models is simply unrealistic at this time, as they do not even perform well as weather prediction models.

 However, it should be understood that RCMs (regional climate models) operate under a set of boundary conditions set by whatever GCM is being used. Hence, if the GCM does not do an adequate job of reproducing the climate signal of a particular region, the RCM will simply mimic those inaccuracies and biases, and propagate the uncertainties even further, albeit at a regional scale. It is not clear how the coupling of a RCM to a flawed GCM can provide more refined insights, any more than can statistical downscaling.

 An editor’s obligation is to publish papers that advance the state of science and of understanding that science. Hydrologists and water management professionals (hydrological and hydraulic engineers) have entered the scientific debate in force, because the GCMs are being advocated for purposes they were not designed for, i.e., watershed vulnerability assessments and infrastructure design. They are now examining whether these models are suitable, using their own perfectly legitimate and peer reviewed methods, as well as statistical tools developed over the course of a century of practical applications. They are not climate sceptics, but are sceptical of the claims of some climatologists and hydroclimatologists that these models are well suited for water management applications.

Our response to the question posed in the title of this editorial is that, while they are getting better, climate models are not (up to) ready for “prime time” yet, at least for direct application to water management problems.

These papers are open to discussion until April 2011. The Editor of the Hydrological Sciences Journal, Zbigniew Kundzewicz, is commended for his serving as a facilitator of all perspectives on the issues raised in the Anagnostopoulos et al. (2010) paper. If the  Anagnostopoulos et al conclusions are robust, it raises the question on the value of spending so much money on providing regional climate predictions decades into the future (e.g., see the 10/21/10 post entitled “The National Science Foundation Funds Multi-Decadal Climate Predictions Without An Ability To Verify Their Skill” .

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