How are decadal oscillations linked to global warming?

One theory is that the present observed trend in global warming is at least partially the result of the decadal oscillations. The effects of the oscillations can be seen in the arctic ocean and the glaciers of Greenland.

During the 1930s and 1940s there was a global warming effect due to the decadal oscillations. During this time the Arctic Ice melted and the Northwest passage was open for a time in 1939 and 1940. Planes landed on the glaciers of Greenland were later covered with very thick layers of ice. These planes have recently been uncovered by the present trend in global warming.

Similar oscillations have been seen in the past. Vikings settled in Greenland, raised crops, grapes and cattle during a warming trend.
A later cooling trend forced the Vikings to abandon their settlements on Greenland and closed the Northwest passage that had allowed the Vikings to settle in what is now Russia.

Another theory is that the oscillations have nothing to do with the present trends in global warming. The oscillations are by definition are always moving back and forth. While the oscillations have a temporary affect on world climate the present trends are thought to be independent of the temporary affect of the oscillations. The theory is that the present trend in global warming is linked to the increased production of Carbon Dioxide.