E-Mail To Linda Mearns On The 2012 BAMS Article On Dynamic Downscaling

source of image from Linda Mearns website

With respect to my post

“The North American Regional Climate Change Assessment Program: Overview of Phase I Results” By Mearns Et Al 2012 – An Excellent Study But It Overstates Its Significance In The Multi-Decadal Prediction Of Climate

I have sent the lead author, Linda Mearns, the e-mail below [and copied to her other co-authors and to several other colleagues who work on downscaling]. I will post her reply, if I receive one and have her permission.

Subject: Your Septmeber 2012 BAMS

Hi Linda

I read with considerable interest your paper

Linda O. Mearns, Ray Arritt, Sébastien Biner, Melissa S. Bukovsky, Seth McGinnis, Stephan Sain, Daniel Caya, James Correia, Jr., Dave Flory, William Gutowski, Eugene S. Takle, Richard Jones, Ruby Leung, Wilfran Moufouma-Okia, Larry McDaniel, Ana M. B. Nunes, Yun Qian, John Roads, Lisa Sloan, Mark Snyder, 2012: The North American Regional Climate Change Assessment Program: Overview of Phase I Results. Bull. Amer.Met Soc. September issue. pp 1337-1362.

It is a very much needed, effective analysis of the level of regional dynamic downscaling skill when forced by reanalyses. In

Castro, C.L., R.A. Pielke Sr., and G. Leoncini, 2005: Dynamical downscaling: Assessment of value retained and added using the Regional Atmospheric Modeling System (RAMS). J. Geophys. Res. – Atmospheres, 110, No. D5, D05108, doi:10.1029/2004JD004721.

and summarized in

Pielke Sr., R.A., and R.L. Wilby, 2012: Regional climate downscaling . what’s the point? Eos Forum, 93, No. 5, 52-53, doi:10.1029/2012EO050008.

Pielke, R. A., Sr., R. Wilby,  D. Niyogi, F. Hossain, K. Dairuku,J. Adegoke, G. Kallos, T. Seastedt, and K. Suding (2012), Dealing with complexity and extreme events using a bottom-up, resource-based vulnerability perspective, in Extreme Events and Natural Hazards: The Complexity Perspective, Geophys. Monogr. Ser., vol. 196, edited by A. S. Sharma et al. 345.359, AGU, Washington, D. C., doi:10.1029/2011GM001086. [copy available from https://pielkeclimatesci.files.wordpress.com/2011/05/r-365.pdf]

you are evaluating the skill and value-added of Type 2 downscaling.

However, you are misleading the impacts communities by indicating that your results apply to regional climate change (i.e. Type 4 downscaling).

I have posted on my weblog today

“The North American Regional Climate Change Assessment Program: Overview of Phase I Results” By Mearns Et Al 2012 – An Excellent Study But It Overstates Its Significance In The Multi-Decadal Prediction Of Climate

which is critical of how you present the implications of your findings.

As you wrote at the end

The Mearns et al 2012 study concludes with the claim that

“Our goal was to provide an overview of the relative performances of the six models both individually and as an ensemble with regard to temperature and precipitation. We have shown that all the models can simulate aspects of climate well, implying that they all can provide useful information about climate change. In particular, the results from phase I of NARCCAP will be used to establish uncertainty due to boundary conditions as well as final weighting of the models for the development of regional probabilities of climate change.”

You write

“We have shown that all the models can simulate aspects of climate well, implying that they all can provide useful information about climate change.”

What you have actually accomplished (and it is significant) is document the upper bound in terms of simulation skill of value-added to reanalyses using dynamic downscaling. However, you have not shown how this study provides skillful information in terms of changes in regional climate statistics on multi-decadal time scales.

I would like to post on my weblog a response from you (and your co-authors if they would like to) that responds to my comments. I will also post this e-mail query.

I have also copied this e-mail to other of our colleagues who are working on dynamic downscaling.

With Best Regards

Roger