Ice core sampling demonstrates that large, rapid, global climactic change is more the norm for the Earth's climate than is climactic stasis. Climactic stasis is wishful thinking by humans, not environmental reality.
Radiocarbon dating of bones and analysis of soils and plant matter shows that Aleutian climate was mild 3500 years ago, and in the 10th century, Greenland's climate, and presumably that of the Arctic nearby, was considerably warmer than today.
Ice-free summers in the Arctic occur approximately every 70 years according to some Russian sources. The Northwest Passage has been open numerous times in the past 100 years. Roald Amundson navigated it in 1903-06. The 104' wooden ship St. Roch sailed through twice in the early 1940s. The Coast Guard ship the USS Storis did it in 1955. There are quite a few other accounts of navigation of the Northwest Passage in the last century, so many that it is actually relatively commonplace. That the Northwest Passage was considered for so long to be a myth is likely due to the mini-ice age from the 16th through the mid 19th centuries rather than because it never existed. That it is open now is simply not that unusual, except in the short-sighted eyes of human memory.
To attribute global climate changes to human impacts on the environment without consideration of the geologic reality of climate change is more an economic tool for those who benefit from such scares than scientific fact.