As climate scientists nervously watch the Arctic and high latitudes this summer — fearing how 2016’s record warmth could push the delicate system — two new pieces of data are hardly consoling.
First, according to researchers with the Rutgers University Global Snow Lab, the entire Northern Hemisphere over the past four months (March, April, May and June) featured the lowest levels of snow on the ground, or snow cover, ever recorded for this particular time period. The data, in this case, go back 49 years.
“It goes along with the pattern we’ve been seeing the last 10 years or so,” said David Robinson, who runs the Global Snow Lab and is the New Jersey state climatologist. “We’ve had so many years in the last decade with low snow cover in the spring.”
Overall, in 2016, the average snow cover across March, April, May and June was just over half a million square kilometers smaller than the previous record low year, 1990.
Not every month during the four-month time period saw a record low for the Northern Hemisphere, but all were quite low. March was the second lowest on record, April was the absolute lowest on record, May was the fourth lowest and June was the third lowest:
In fairness, we shouldn’t make too much of this particular “record,” because if you just take the last three months (April, May, June), rather than the last four, then the record goes away — and you’re merely in second place.
On the other hand, if you take March, April and May — the Northern Hemisphere spring — you have a record again (see below). So this is partly a matter of definition.
Nonetheless, the key point is that overall levels of snow on the ground or in mountain snowpack are very low this year, and this is part of a trend — which, of course, we would expect on a warming planet.
That trend will have vast consequences for water supplies, wildfires and the warming of the Earth itself. For after all, low snow cover means that the Earth has less reflectivity or “albedo” — so it warms up more from the sun’s rays.
“Your energy is either being reflected, and thrown back into space, or it’s being used to melt the snow,” said Robinson. “If the snow’s not there, it’s going to be absorbed by the surface, it’s going to warm up the surface, which in turn will warm the atmosphere, and it’s also going to dry out any water on the surface, which also is going to heat the atmosphere. So it really sets you up for a warmer pattern.”
Robinson says if there is any indicator of the consequences of low snow so far this year it is the enormous and devastating wildfire that engulfed Fort McMurray, Canada, and the surrounding forests.
“The snow is out of the boreal forest early, temperatures warmed up to temperatures they never warm up to when there’s snow around, and that was a large part of desiccation of the forest and really helped to fuel that fire,” he said.
Robinson also notes that record or near record low amounts of Northern Hemisphere snow in March, April, May and now June show there has basically been no reprieve. Instead, as the band of Northern Hemisphere melting progressed farther and farther north this year — since lower latitude snow melts earlier in the year than higher latitude snow — high levels of melt racked up steadily across the latitudes.
“This year, we saw it across the board, from the mid latitudes up toward the pole,” he said.
The latest numbers on snow cover come paired with a barrage of data suggesting that Arctic sea ice — the counterpart to snow cover over the Northern Hemisphere oceans — has also set repeated record lows this year. January, February, April and May of this year all saw record lows for Arctic sea ice extent.
And now, the National Snow and Ice Data Center in Boulder, Colo., has announced that June 2016, too, saw record low average Arctic sea ice extent (see above).
If there’s any slight good news here, it’s that nonetheless, it looks like this year may fall a bit shy of the all-time record year, 2012, when the absolute record low for Arctic sea ice arrives in September.
Still, if you look at all the charts above, there’s only one thing you can conclude. We are moving into a world with a lot less reflective snow and sea ice in the Northern Hemisphere than there used to be. The consequences of this momentous trend aren’t even completely understood yet. But they will not be small.