Researches studying arctic ice cores have concluded that soot released by industrial activities has long influenced the local arctic climate. Deposits of soot, particularly bad from 1851 to 1951, make for darker snow, which absorbs more heat than cleaner snow would.

Other chemicals found in the ice cores – which cover the years 1788 through 2002 – show that prior to the 1850s most soot came from forest fires or other natural causes. The soot found from 1850 onwards came from industrial emissions, especially coal burning.

The soot levels peaked between 1906 and 1910, but remained high for many more years. During the peak years the warming effect of soot in the arctic is estimated to have been eight times what it was prior to the industrial revolution.

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