From A.D. 900 to A.D. 1100, a period scientists refer to as the "Medieval Climate Optimum," global temperatures were warmer on average than at present. The weather was so mild that the Vikings established colonies and farms in Greenland (in regions that were, in fact, green). In the 1300s, global temperatures began to drop, plunging the world into the Little Ice Age. The Vikings' crops and livestock in Greenland began to fail, the Vikings left, and Greenland was covered with ice. About 1850, Earth's climate began to gradually warm, ending the Little Ice Age; this warming lasted until about 1940. Beginning in 1940, temperatures leveled off and began to drop slightly once again.
If the air pollution was effecting Greenland, then it should be effecting us too! Which it is not!!