Coloration evidence for natural selection J. Bowler wrote that Darwin's theory In his 1889 book "Darwinism", the naturalist Alfred Russel Wallace considered the white coloration of Arctic animals. He recorded that the Arctic fox, Arctic hare, ermine and ptarmigan change their colour seasonally, and gave "the obvious explanation", that it was for concealment. The modern ornithologist W. L. N. Tickell, reviewing proposed explanations of white plumage in birds, writes that in the ptarmigan "it is difficult to escape the conclusion that cryptic brown summer plumage becomes a liability in snow, and white plumage is therefore another cryptic adaptation." All the same, he notes, "in spite
Arctic haze the opposite effect of trapped warmth beneath the cloud cover. During the Arctic winter, however, there is no sunlight to reflect. In the absence of this cooling effect, the dominant effect of changes to Arctic clouds is an increased trapping of infrared radiation from the surface. Ship emissions, mercury, aluminium, vanadium, manganese, and aerosol and ozone pollutants are many examples of the pollution that is affecting this atmosphere, but the smoke from forest fires is not a significant contributor. Some of those pollutants figure among environmental effects of coal burning. Due to low deposition rates, these pollutants are not yet