Polar amplification
Polar amplification also referred to as Arctic amplification, is the greater temperature increases in the Arctic compared to the earth as a whole as a result of the effect of feedbacks and other processes[1] It is not observed in the Antarctic, largely because the Southern Ocean acts as a heat sink and the lack of seasonal snow cover.[2] It is common to see it stated that "Climate models generally predict amplified warming in polar regions", e.g. Doran et al.[3] However, climate models predict amplified warming for the Arctic but only modest warming for Antarctica.[2]
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Arctic Temperature Trend 1987–2007 -
Antarctic Temperature Trend 1981–2007 (note: temperature scale differs considerably from the Arctic plot)
As far back as 1896, the Swedish scientist Svante Arrhenius hypothesized that changes in the concentration of carbon dioxide in Earth’s atmosphere could alter surface temperatures. He also suggested that changes would be especially large at high latitudes.
Arrehenius didn’t get every detail right, but his argument has proven to be pretty sound. Since the mid-20th Century, average global temperatures have warmed about 0.6°C (1.1°F), but the warming has not occurred equally everywhere. Temperatures have increased about twice as fast in the Arctic as in the mid-latitudes.Cite error: The <ref> tag has too many names (see the help page).
Why are temperatures warming faster in the Arctic than the rest of the world? The loss of sea ice is one of the most cited reasons. When bright and reflective ice melts, it gives way to a darker ocean; this amplifies the warming trend because the ocean surface absorbs more heat from the Sun than the surface of snow and ice. In more technical terms, losing sea ice reduces Earth’s albedo: the lower the albedo, the more a surface absorbs heat from sunlight rather than reflecting it back to space.
However, other factors contribute as well, explained Anthony Del Genio, a climatologist from NASA’s Goddard Institute for Space Studies. Thunderstorms, for instance, are much more likely to occur in the tropics than the higher latitudes. The storms transport heat from the surface to higher levels of the atmosphere, where global wind patterns sweep it toward higher latitudes. The abundance of thunderstorms creates a near-constant flow of heat away from the tropics, a process that dampens warming near the equator and contributes to Arctic amplification. From NASA, Earth Observatory, written by Adam Voiland.
See also
References
- ^ Arctic Climate Impact Assessment - International Arctic Science Committee
- ^ a b "Antarctic cooling, global warming?". RealClimate. 3 December 2004.
- ^ Doran, Peter T.; Priscu, John C.; Lyons, W. Berry; Walsh, John E.; Fountain, Andrew G.; McKnight, Diane M.; Moorhead, DL; Virginia, RA; Wall, DH (31 January 2002). "Antarctic climate cooling and terrestrial ecosystem response". Nature. 415 (6871): 517–20. doi:10.1038/nature710. PMID 11793010.