Probably the trickiest part of determining the impact of hemispheric imbalance is dealing with the amplification of the surface temperatures used as the primary metric. On the whole the data is remarkably accurate and well organized. What the data is supposed to represent versus what it actually indicates is a bit of a problem though. The surface air temperature is measured approximately two meters above the ground surface at an average altitude of ~680 meters. The less dense air tends to amplify the variability plus there are many more land issues than ocean issues. Most of the warming is over land and in the northern hemisphere oceans at first glance, but both the land and the NH oceans due to the bottleneck between latitudes 30N and 60N tend to amplify overall temperatures.
The well mixed Southern Hemisphere oceans do have an advantage in the surface temperature metric department with less "active" land mass to create noise. The Antarctic and moist tropics land masses are much more stable than the NH especially the 30N to 60N region.
I am sure there will be a few questions on this scaling, but the Toggweiler Shifting Westerlies paper mentions how much impact on surface temperature a shift in the Inter-Tropical Convergence Zone (ITCZ) can have when compared to CO2 forcing. There have been quite a few issues created by ignoring internal variability and "amplification" due to inconsistent regional climate "Sensitivity" that will prove to be rather embarrassing sometime in the near future if my thoughts are correct.