The Inuit, the natives of high northern latitudes, have noticed climate change for years, and it is only getting worse [LINK]. A lot of popular press have mentioned that "experts" and/or "scientists" think the polar region will feel climate change first and worst. This seems to be an accurate statement, based on current understanding of global warming scenarios. The effect is usually described as polar amplification, conveniently described by a recent RealClimate.org column [LINK]. Most of the time people like to talk about the ice-albedo feedback to support polar amplification. That is basically the idea that the change in atmospheric composition leads to warmer surface conditions, which melts snow or sea-ice, which decreases the albedo (reflectance) and leads to more warming. This can be coupled with myriad other positive feedbacks to get a larger effect. There are also dynamic arguments that the circulation (polar vortices, e.g.) are changing in response to warming. Michael Winton (GFDL/NOAA) seems to think the models say the change in clouds and water vapor are at least as important as surface effects [PDF]. I like to think about it the other way around, that is, the atmosphere warms, but the tropics don't warm as much as they "should," which forces more energy to higher latitudes by various heat transports. The increase in poleward heat transport is manifest by larger outgoing longwave radiation at the top of the atmosphere and higher temperatures to provide that radiation. I'll have to look more deeply into the literature to see if my view is at odds with the accepted ways of looking at polar amplification, but I think it should be pretty much the same. They describe the processes that result from increased poleward heat transport (like more precipitation at high latitudes leading to more melting of snow and ice, and definitely more eddy energy (storms) moving tropospheric moisture poleward from the tropics and subtropics).
SSRD supplied the first WaPo article linked above, and set me off on this tangential discussion of poleward heat transport... thanks SSRD.
2 comments:
I like to think about it the other way around, that is, the atmosphere warms, but the tropics don't warm as much as they "should," which forces more energy to higher latitudes by various heat transports.
This is the most interesting piece of the analysis to me, from a physics point of view. Can you elaborate on why they tropics dont' warm as much as they "should"?
Ah, the tropical thermostat. I don't think I'll elaborate too much, except to say that the tropics are remarkably stable in temperature (and probably relative humidity). Some estimates have significant variations over paleoclimatic timescales, but those are still in the minority. Understanding why the tropics don't warm very much with increased forcing is on ongoing research topic. Most work focuses on negative feedbacks associated with clouds... e.g. Ramanathan & Collins (1991), Hartmann & Michelson (1993), Larson & Hartmann (1999), Miller (1997), and the ever-discredited Lindzen et al (2000), to name a few.
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