Disaster on thin ice

Disaster on thin ice
May 1, 2000

Sure is nice out! But watch that spring in your step. As the black-and-white of winter is forgotten in a burst of colorful daffodils and tulips, maybe we should be worrying about melting the polar ice cap.

In response to Konstantin Ya. Vinnikov’s highly publicized paper on the melting of arctic sea ice since 1950, my colleagues and I looked at summer temperatures and found no warming. In fact, annual readings only begin to head upward around 1988. Apparently, whatever initiated the melting had little to do with people, even if what continued that warming does.

Now comes a new, more comprehensive study of Arctic Ice by Clara Deser, John Walsh, and Michael Timlin, published in the latest issue of Journal of Climate. The second author, Walsh, has a prolific and long-standing record of expertise on the polar cap.

Deser and colleagues quantified the rates of ice disappearance and found that the rate of summer decline, since the record begins in 1957, is 0.4 percent per year, or 40 percent per century. At this rate, summer ice will be gone around the year 2210. The winter decline is very small, at 0.06 percent per year, or 6 percent per century. It would disappear somewhere around the year 3625. Anyone who says our energy technology will look anything like today’s in the year 2200 probably thinks Thomas Jefferson owned a jet plane.

We may have been treated to headlines screaming that 40 percent of the Arctic ice has melted as a result of human activity, but the truth is somewhat less alarming. Integrating the Deser data to a yearly basis reveals that the decline has been 0.23 percent per year. For the last half of this century, this works out to an integrated value of about 12 percent.

Remember that the closer you get to the pole, the harder it gets to melt things, which may explain why the declines in ice shown in this paper are linear (constant) despite the general notion that warming tends to increase with latitude. All of which means that somewhere around the end of this century (i.e., the year 2100), the integrated ice loss would be around 36 percent, assuming business as usual with regard to fossil fuel emissions.

Aye, there’s the rub: No one really believes that, 100 years from now, we’ll be using much of the energy system we’re using now. Truth be told, no one, not even the U.N.’s Intergovernmental Panel on Climate Change, has the ability to predict the shape of this system even 50 years hence. The best bet, then, seems to be that, under the worst-case scenario, we will lose a net annual average of about one-third of our polar ice as a consequence of the economic expansion created by fossil fuels.


Reference

Deser, C., et al., 2000. Arctic sea ice variability in the context of recent atmospheric circulation trends. Journal of Climate, 13, 617–633.