Lake Superior is the largest and northernmost Great Lake, containing almost three times as much water as Lake Michigan, the second largest in volume. In fact, it contains more water than the other Great Lakes combined. Which should mean that it’s cold.

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Calling it hot is a stretch — but all of that water is heating up far more than expected. From Climate Central (which is also the source of the graph):

As the above chart shows, based on the 30-year average, the lake’s average water temperature should be in the mid-50s. But thanks to scant lake ice cover this past winter, along with a rare March heat wave and warmer-than-average weather since then, the lake began warming earlier than normal, and that warming has kept right on going. Wintertime ice cover on the Great Lakes was the lowest observed since such records began in 1980.

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The chart itself is pretty amazing. At no point in 2012 has the surface temperature been below average, and it’s now spiking well above. Temperatures today range from 70 degrees at the southern shore to 60 at the northern-most points.

Click to embiggen.

(NOAA’s Great Lakes Environmental Research Laboratory — the fun-to-say GLERL — also has a near-real-time animated map of surface currents, but that is mentioned solely because it is cool.)

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Over the long term, all of the lakes are getting warmer, leading perspicacious scientists to think that this might be linked to that “climate change” thing.

Data shows a long-term warming trend throughout the Great Lakes, which may be related to manmade climate change. According to George Leskevich, a physical research scientist with the Great Lakes Environmental Research Laboratory in Ann Arbor, Mich., there is also a long-term downward trend in Great Lakes wintertime ice cover, although there is considerable year-to-year variability.

The really bad news is for the Canadians who live east of the lake.

Ironically, if the lakes enter the fall with record warm temperatures, it could herald an above-average season for lake effect snow, which occurs when cold, dry air blows across large expanses of comparatively milder waters.

At which point we’ll hear all about how global warming is a myth.

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