Re: “Dust and its effect on heating, cooling” by Martin Hertzberg, April 27:
In his criticism of an earlier letter by Tim Lyon, Mr. Hertzberg claims that Mr. Lyon cherry-picked human-caused global-warming anecdotes to bolster his case. I suggest that Mr. Hertzberg ignored several aspects of science in claiming that dusty, darkened snow will emit energy back into space and equally counter the daytime absorption of energy. On one hand I presume he is referring to Black Body Radiation, which explains energy absorption and emission by heated bodies. On the other hand, Mr. Hertzberg references his own work in this area; I read his abstract, which predominantly challenges the “so-called ‘greenhouse-effect.'”
Even if I accepted his claims in this area, he deliberately overlooks that the dust, once on the surface of the snow, warms and melts into the snow surface. Most all of the energy it absorbs isn't given back up to the atmosphere but causes further energy absorption and melting.
Further, once melted, the snow consumes a lot of “cold” to refreeze but the nighttime cooling of the surface isn't in a position to accomplish it. (Profuse apologies to physics teachers everywhere but it takes a lot of “cold” snow to refreeze liquid water.)
For those that wish to do their own research: Spread a bit of sand on some snow that gets sun. Check back occasionally and see if it melts and/or evaporates faster than clean snow. Check back the next morning and see if the snow that disappeared the previous day has returned.
Neil Groundwater, Breckenridge