Arctic Amplification

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The observation that the Arctic has warmed substantially faster than the global mean - work published in 2022 put the factor at close to four times over the period since 1979, higher than the two-to-three times commonly quoted before it. Several mechanisms contribute and their relative weight is still argued: the ice-albedo feedback, in which retreating bright ice exposes dark ocean that absorbs more solar energy; the lapse-rate feedback, in which the Arctic atmosphere warms in a bottom-heavy way that radiates heat to space less efficiently; changes in poleward heat and moisture transport; and cloud effects. The asymmetry is important for this Journey because it does not have an Antarctic twin - the southern hemisphere has an ocean where the north has an ocean basin ringed by land, and a continent where the north has open water, and the two do not respond alike.