It is argued that the influence of the Indian ocean on the North Atlantic climate, particularly on the NAO, may be much larger than previously thought. This influence has generally been assessed by forcing atmospheric GCMs with prescribed anomalous SSTs in the Indian ocean. Such an approach assumes that the Indian ocean anomalies act as a forcing, when in fact they are often largely a response to changes in the Walker circulation associated with the ENSO phenomenon. In this study, the global impacts of such remotely forced Indian ocean changes are investigated in GCM simulations with and without anomalous air-sea coupling in the Indian ocean. A dramatically stronger NAO response is obtained in the coupled simulations. The weaker response in the prescribed-SST simulations is due to a previously unappreciated spurious transient-eddy feedback. Briefly, the erroneous surface heat fluxes in those simulations generate spuriously larger deep convective heating variability over the Indian ocean, stronger eddies in the circumpolar jet stream waveguide, and enhanced eddy-mean flow interactions over the Atlantic. This spurious enhancement is associated with stronger incursions of low potential vorticity subtropical air into the northern Atlantic middle latitudes, whose net effect is to force a negative-NAO error pattern reminiscent of the classic pattern of north Atlantic blocking. This may be the basic reason why numerous previous prescribed-SST simulations have severely underestimated the magnitude of the observed NAO trend over the past half century.