I enjoyed the article “The thinning of Arctic sea ice” by Ron Kwok and Norbert Untersteiner (PHYSICS TODAY, April 2011, page 36). I suggest that the possible cause of the 1 W/m2 surplus heating is from airline traffic in the vicinity. I say this for the following reasons:
‣ In the energy balance, Kwok and Untersteiner write, “the solar and atmospheric radiation terms dominate.”
‣ The authors also write, “Radiative energy fluxes from the atmosphere and the annual advection . . . are two orders of magnitude larger than 1 W/m2.”
‣ People from the US Midwest observed that the sky became much less hazy during the flight moratorium after 9/11.
‣ Jet contrails contain water vapor and, more importantly, carbon particles that act as cloud condensation nuclei that enhance the high cloud layer.
‣ “High, thin cirriform clouds (composed mostly of ice) tend to promote a net warming effect.”1
‣ The time frame of the warming coincides with the development of jet air travel.
It seems quite possible that a little extra high cloudiness produced by jet flights in the area of the Arctic causes the little extra heating needed for the melting.
