North-West Passage was Open in the 1940's - Oops The Global Warming Crowd Forgot to Tell us That

Roy Spencer has an interesting article regarding the fact that ...

"Contrary to what you have been led to believe, there is no solid published evidence that has ruled out a natural cause for most of our recent warmth – not one peer-reviewed paper. The reason: our measurements of global weather on decadal time scales are insufficient to reject such a possibility. For instance, the last 30 years of the strongest warming could have been caused by a very slight change in cloudiness. What might have caused such a change? Well, one possibility is the sudden shift to more frequent El Niño events (and fewer La Niña events) since the 1970s."

"That shift also coincided with a change in another climate index, the Pacific Decadal Oscillation.
The associated warming in Alaska was sudden, and at the same time we just happened to start satellite monitoring of Arctic sea ice. Coincidences do happen, you know…that’s why we have a word for them.

"We make a big deal out of the “unprecedented” 2007 opening of the Northwest Passage as summertime sea ice in the Arctic Ocean gradually receded, yet the very warm 1930s in the Arctic also led to the Passage opening in the 1940s. Of course, we had no satellites to measure the sea ice back then." Read here and here.