Long-term surface temperature changes caused by fluctuations in the atmospheric greenhouse gas (GHG) loading are most pronounced in polar regions, with the recent polar warming being greatest during the cold season. The leading theory for this polar amplification is the ice-albedo feedback mechanim whereby a melting of snow and ice reduces the surface reflectivity of solar radiation, promoting further warming of the surface. The relevance of this mechanism has been questioned recently, and in this study we put forward an alternative theory which states that enhanced localization of tropical convective heating intensifies poleward propagating atmospheric planetary waves (these waves, which depend upon the rotation and sphericity of the earth, are more commonly known as Rossby waves) which then act to warm polar regions through an enhancement in adiabatic warming and poleward heat flux. The premise of this theory, i.e., GHG warming causes tropical convective heating to be more localized, is inferred the Clausius-Clapeyron relationship, that a warmer climate has a more intense spatial pattern of precipitation (P) minus evaporation (E); because P-E is not zonally uniform, the condensational heating is expected to become increasingly localized in a warmer climate.

Test results of this theory with models and global datasets show that the planetary-wave-driven warming occurs on relatively short, intraseasonal time scales, in the form of so-called atmospheric teleconnection patterns. However, it is the change in the frequency of occurrence of these short time-scale teleconnections that drives the interdecadal time-scale polar warming. The implication is that climate model projections of future polar climate can be made more accurate if their representation of tropical P-E and teleconnection patterns can be improved. Because atmospheric teleconnection patterns are closely linked to weather events, the finding of this study also implies that particular weather events will become more frequent and/or intense as GHG warming continues.