NOAA scientists are trying to answer the title question. A new report Arctic nearly free of summer sea ice during first half of 21st century takes a stab at it. The results are bit perplexing.
For scientists studying summer sea ice in the Arctic, it’s not a question of “if” there will be nearly ice-free summers, but “when.” And two scientists say that “when” is sooner than many thought — before 2050 and possibly within the next decade or two.
James Overland of NOAA’s Pacific Marine Environmental Laboratory and Muyin Wang of the NOAA Joint Institute for the Study of Atmosphere and Ocean at the University of Washington, looked at three methods of predicting when the Arctic will be nearly ice free in the summer. The work was published recently online in the American Geophysical Union publication Geophysical Research Letters...
“There is no one perfect way to predict summer sea ice loss in the Arctic,” said Wang. “So we looked at three approaches that result in widely different dates, but all three suggest nearly sea ice-free summers in the Arctic before the middle of this century.”
No perfect way? Well, you could look at the ice volume trend and do a simple extrapolation.
I took this graph from Death Spiral Watch: Experts Warn ‘Near Ice-Free Arctic In Summer’ In A Decade If Volume Trends Continue. You can see that we're rapidly running out of ice to lose.
However, great complexity must be introduced where simplicity would probably suffice.
Overland and Wang emphasized that the term “nearly” ice free is important as some sea ice is expected to remain north of the Canadian Archipelago and Greenland.
The “trendsetters” approach uses observed sea ice trends. These data show that the total amount of sea ice decreased rapidly over the previous decade. Using those trends, this approach extrapolates to a nearly sea ice-free Arctic by 2020.
The “stochasters” approach is based on assuming future multiple, but random in time, large sea ice loss events such as those that occurred in 2007 and 2012. This method estimates it would take several more events to reach a nearly sea ice-free state in the summer. Using the likelihood of such events, this approach suggests a nearly sea ice-free Arctic by about 2030 but with large uncertainty in timing.
The “modelers” approach is based on using the large collection of global climate model results to predict atmosphere, ocean, land, and sea ice conditions over time. These models show the earliest possible loss of sea ice to be around 2040 as greenhouse gas concentrations increase and the Arctic warms. But the median timing of sea ice loss in these models is closer to 2060.
There are several reasons to consider that this median timing of sea ice loss in these models may be too slow.
Hmmm... That "modelers" approach looks pretty useless. The models seem to be completely out of touch with the actual data (= Reality). These NOAA scientists are a little sensitive about that.
“Some people may interpret this to mean that models are not useful. Quite the opposite,” said Overland. “Models are based on chemical and physical climate processes and we need better models for the Arctic as the importance of that region continues to grow.”
I laughed out loud when I read that. Perhaps a translation is called for.
Look, man, 90% of our funding is wrapped up in these fucking models. Clearly those models suck, they're about as useful as teats on a boar hog for predicting summer sea ice in the Arctic. Obviously we need better models for the Arctic as the importance of that region continues to grow.
We need to improve those models, OK? And that means you'll need to pony up more money so we can do just that.
Give us a break!
You can expect to see a nearly ice-free summer in the Arctic by 2020 if the data is anything to go by. We get a fast albedo positive feedback when there is less sea ice. In clear water, Arctic ocean waters absorb far more heat than they would have if the sea ice were reflecting energy from the sun back into the atmosphere.
Sea ice has a much higher albedo compared to other earth surfaces, such as the surrounding ocean. A typical ocean albedo is approximately 0.06, while bare sea ice varies from approximately 0.5 to 0.7. This means that the ocean reflects only 6 percent of the incoming solar radiation and absorbs the rest, while sea ice reflects 50 to 70 percent of the incoming energy. The sea ice absorbs less solar energy and keeps the surface cooler.
More heat absorption melts more ice, which leads to more heat absorption, which melts more ice ... you get the idea.
By the time we get a nearly ice-free summer in the Arctic—in 2019, to pick a date—those new and improved models might actually be in agreement with Reality.
Progress marches on!