One of the biggest predictors of global warming is the retreat of sea ice in the high northern latitudes. As oceans warm, the ice will take longer to form in the winter, and retreat faster in the spring. Scientists, therefore, have been watching the ice north of Canada very carefully. What they're seeing isn't very hopeful.
This picture, from the Terra Earth-observing satellite, shows the state of sea ice as it was on August 17. This region is the so-called Northwest Passage -- a waterway through the Canadian archipelago connecting the Atlantic and Pacific oceans. Usually the sea ice prevents regular trade routes from being utilized there. But over the past few years -- <sarcasm>coincidentally</sarcasm> the time when scientists say global warming is accelerating -- the sea ice has thinned considerably. In 2007 the sea ice underwent a record thinning and the passage opened enough for navigation. This year, the ...
