Background
The authors write that "midlatitude storm tracks are marked by regions frequented by baroclinic waves and their associated surface cyclones," which bring with them "strong winds and heavy precipitation, seriously affecting regional weather and climate." They also note that such storms "transport large amounts of heat, momentum and moisture poleward," making up "an important part of the global circulation." And they say that how these storm tracks may change as a result of global warming "is thus of huge societal interest."

What was done
Chang et al. say they used "storm-track activity derived from ERA-Interim [European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40; Uppala et al. 2005)] data as the current best estimate to assess how well models that participated in phase 3 of the Coupled Model Intercomparison Project (CMIP3; Meehl et al. 2007) that were considered in the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4; Solomon et al. 2007) do in simulating storm-track activity."

What was learned
The four researchers report that (1) "only 2 of the 17 models have both the Northern Hemisphere [NH] and Southern Hemisphere [SH] storm-track activity within 10% of that based on ERA-Interim," (2) "four models simulate storm tracks that are either both significantly (>20%) too strong or too weak," (3) "the SH to NH ratio of storm-track activity ... is biased in some model simulations due to biases in midtropospheric temperature gradients," (4) "storm tracks in most CMIP3 models exhibit an equatorward bias in both hemispheres," (5) "some models exhibit biases in the amplitude of the seasonal cycle," (6) models having a strong (weak) bias in storm-track activity also have a strong (weak) bias in poleward eddy momentum and heat fluxes, suggesting that wave-mean flow interactions may not be accurately simulated by these models," and (7) "preliminary analyses of Fifth Assessment Report (AR5)/CMIP5 model data suggest that CMIP5 model simulations also exhibit somewhat similar behaviors."

What it means
Meet the new models, same as the old models ... and don't get fooled again.

References
Meehl, G.A., Covey, C., Delworth, T., Latif, M., McAvaney, B., Mitchell, J.F.B., Stouffer, R.J. and Taylor, K.E. 2007. The WCRP CMIP3 multi-model dataset: A new era in climate change research. Bulletin of the American Meteorological Society 88: 1383-1394.

Solomon, S., Qin, D., Manning, M., Marquis, M., Averyt, K., Tignor, M.B., Miller Jr., H.L. and Chen, Z. (Eds.). 2007. Climate Change 2007: The Physical Science Basis. Cambridge University Press, Cambridge, United Kingdom.

Uppala, S.M., Kallberg, P.W., Simmons, A.J., Andrae, U., Da Costa Bechtold, V., Fiorino, M., Gibson, J.K, Haseler, J., Hernandez, A., Kelly, G.A., Li, X., Onogi, K., Saarinen, S., Sokka, N., Allan, R.P., Andersson, E., Arpe, K., Balmaseda, M.A., Beljaars, A.C.M., Van De Berg, L., Bidlot, J., Bormann, N., Caires, S., Chevallier, F., Dethof, A., Dragosavac, M., Fisher, M., Fuentes, M., Hagemann, S., Holm, E., Hoskins, B.J., Isaksen, L., Janssen, P.A.E.M., Jenne, R., McNally, A.P., Mahfouf, J.-F., Morcrette, J.-J., Rayner, N.A., Saunders, R.W., Simon, P., Sterl, A., Trenberth, K.E., Untch, A., Vasiljevic, D., Viterbo, P. and Woollen, J. 2005. The ERA-40 reanalysis. Quarterly Journal of the Royal Meteorological Society 131: 2961-3012.