Background
The authors write that "current state-of-the-art climate models fail to capture accurately the path of the Gulf Stream and North Atlantic Current," which model failure "leads to a warm bias near the North American coast, where the modeled Gulf Stream separates from the coast further north, and a cold anomaly to the east of the Grand Banks of Newfoundland, where the North Atlantic Current remains too zonal."

What was done
Using a high-resolution coupled atmosphere-ocean model (HiGEM), which is described in detail by Shaffrey et al. (2009), Keeley et al. analyzed the impacts of the sea surface temperature (SST) biases created by the model in the North Atlantic in winter - approximately 8°C too cold to the east of the Grand Banks of Newfoundland, and 6°C too warm near the east coast of North America - on the mean climatic state of the North Atlantic European region, along with the variability associated with those model-induced SST biases.

What was learned
The three UK researchers say their results show that the model-induced SST errors produce a mean sea-level pressure response that is similar in magnitude and pattern to the atmospheric circulation errors in the coupled climate model," and they say that they also suggest that "errors in the coupled model storm tracks and North Atlantic Oscillation, compared to reanalysis data, can also be explained partly by these SST errors."

What it means
In the concluding sentence of the abstract of their paper, Keeley et al. suggest that "both [1] the error in the Gulf Stream separation location and [2] the path of the North Atlantic Current around the Grand Banks play important roles in affecting the atmospheric circulation," and they say that "reducing these coupled model errors could improve significantly the representation of the large-scale atmospheric circulation of the North Atlantic and European region." Thus, we can only hope that this major shortcoming of current state-of-the-art climate models will be corrected in future versions that result from the seemingly never-ending process of seeking to adequately and properly represent all of the essential elements of earth's amazingly complex system of climate regulation.

Reference
Shaffrey, L.C., Stevens, I., Norton, W.A., Roberts, M.J., Vidale, P.L., Harle, J.D., Jrrar, A., Stevens, D.P., Woodage, M.J., Demory, M.E., Donners, J., Clark, D.B., Clayton, A., Cole, J.W., Wilson, S.S., Connolley, W.M., Davies, T.M., Iwi, A.M., Johns, T.C., King, J.C., New, A.L., Slingo, J.M., Slingo, A., Steenman-Clark, L. and Martin, G.M. 2009. U.K. HiGEM: The new U.K. High-Resolution Global Environment Model: model description and basic evaluation. Journal of Climate 22: 1861-1896.