Are The IPCC Global Climate Model Multi-Decadal Global Model Predictions Accurate On Regional And Local Spatial Scales?

There is an editorial [h/t to Michael Lenaghan!]

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

which raises the broader question:

Are The IPCC Global Climate Model Multi-Decadal Global Model Predictions Accurate On Regional And Local Spatial Scales?

The editorial includes the text

“In general, despite the considerable progress achieved, GCMs still cannot reconstruct the important details of the climate at smaller scales (regional to local). They cannot resolve sub-grid processes, e.g. related to topography and land use. Hence, other techniques, such as regional climate models (RCMs), or downscaling methods, have been developed. A typical RCM grid is of the order of 10–50 km, although some climate simulations have used smaller grids, but usually only for a shorter temporal horizon of simulations. Alternatively, statistical downscaling can be used, based on relationships linking large-scale atmospheric variables (predictors) and local/regional climate variables (predictands),
cf. Wilby (2010).

However, it should be understood that RCMs 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.”

This is an important issue since even if the global climate models could accurately predict an annual global average of any climate variable [a big IF which is still being debated], if they cannot skillfully predict the spatial and temporal scales that matter in terms of environmental and social impacts (such as water resources), they are of no value. Indeed, as a result of the fine-scale spatial resoluton that regional downscaling can provide, they can mislead policymakers into accepting the predictions as skillful when they are not.

I have discussed this subject in papers and in a variety of weblog posts; e.g. see

Can Regional Vulnerability Be Accurately Assessed By Using Multi-Decadal Global Model Predictions?

where I wrote

“The use of multi-decadal global climate models as the driver of determing hotspots [the most responsive regions to climate change], however, is dependent on these global models being able to skillfully predict regional climate change….As we have reported on the Climate Science weblog, there is no skill in predicting multi-decadal regional climate (see).

Thus, how can these multi-decadal models be used to identify hot spots? These models do not even include all of the first order climate forcings and feedbacks…..

The answer is that they cannot…..Actually “hot spots” are likely to be quite different when the actual vulnerability of regions are assessed using a bottom-up (“place-based”) perspective in which all threats (social as well as environmental) are included.”

The clear answer to the question

Are The IPCC Global Climate Model Multi-Decadal Global Model Predictions Accurate On Regional And Local Spatial Scales?

is NO.  I invite climate science colleagues to e-mail me to present a counter viewpoint to this answer which we will present as a guest post.

Comments Off on Are The IPCC Global Climate Model Multi-Decadal Global Model Predictions Accurate On Regional And Local Spatial Scales?

Filed under Climate Models, Q & A on Climate Science

Comments are closed.