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The Future of Freezing

by Ben Strauss

Enjoy March while it's still cold!

That's the message from a new interactive map of high-resolution climate projections produced by Climate Central. The map shows freezing March temperatures retreating northward this century like a routed army. The retreat would be about half the speed under a low carbon pollution scenario.

Click on the image above to view the map

Of course, the idea of thawing temperatures seems pretty nice at the end of a long, snowy winter like the one we just had in the US (most other places were warmer than usual). And the trend does promise earlier starts for golfers, gardeners and farmers in the future.

On the other hand, warmer Marches would also mean earlier snowmelt. Across the American West, early snowmelt years have already been linked to drier rivers and forests later in the summer, and very much higher wildfire activity (see this video on the situation in Washington State). Scientists project these problems will get only worse with further warming. Other challenges expected include water shortages for farm irrigation and trouble for trout and other cold-water stream life (explored more in this video about Montana).

Assuming we continue to emit carbon pollution at a high rate, Climate Central’s maps project majority or complete loss, by the end of the century, of areas with average March temperatures below freezing in all states analyzed. The biggest losers will be Minnesota, Montana, and North Dakota, in terms of total area; but seven states, from Arizona to Wisconsin, are projected to lose just about every frozen March acre they now possess. For a full tally, see this table. This year, it's interesting to note that while Washington, DC had record-breaking winter snow, temperatures never dipped below freezing in March — a new record for warmth.

Speaking of melting, the thaw season has just begun in the Arctic, where the sun has now made its way above the horizon. Over recent decades, the Arctic has been the fastest-warming region on the planet, a pattern scientists expect to continue. The trends underway and their consequences are neatly visualized in this short new video, based mainly on data gathered by NASA satellites. They make projections of warming March months in the US look tame.

Click on the image above to view the video.

For example, Greenland is shedding ice, and the average net loss per year from 2004 to 2007 was about 25 times the average from 1992-2002. How much of this shift may have come from natural variation and how much from human-caused warming is difficult to assess, but two things are clear. Arctic warming means Greenland ice loss, and Greenland ice loss means rising seas. Recent scientific studies that take Arctic trends into account generally project more than a three-foot rise this century.

Another key trend just coming to light is that the crust of ice that covers parts of the Arctic Ocean has been getting thinner over recent decades. Most observers' attention has been focused on the shrinking extent of Arctic sea ice — but the ice appears to be thinning even faster. And just-published research (subscription required) suggests that the ice may be thinner yet than we thought. The thinner ice gets, the more vulnerable it becomes to future disintegration.

Now, when ice floating in the sea melts, it does not raise sea level — just like melting ice cubes don't cause a glass of water to overflow. However, sea ice is bright and white, and reflects the sun's energy back into space — like a giant planetary heat shield. As sea ice retreats, more dark ocean is exposed, absorbing the sun's heat, and warming the Arctic further.

Which brings us back to Greenland.

So, as we dump our winter coats and turn our minds to spring — let's take one more moment to reflect on the cold!

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