Politics Blog

Madcap: Deniers latch onto larger ice sheet

If Bellingham gets a foot of snow this November, would that mean we can dismiss climate change?

All of us, liberals, conservatives and journalists, have become well enough educated on the difference between weather and climate to know that the answer is "no." One cold winter, one great ski season, one year when Artist Point never gets to open does not augur the end of global warming.

Now comes a report that is generating chatter among the AGW* deniers: The arctic ice cap, which is right about now at its annual minimum, is 60 percent bigger than it was at this time in 2012.

To read the Daily Telegraph, a large-circulation conservative newspaper out of London, scientists are heralding a half-century cooling period that began about 15 years ago.

At a climate change seminar for journalists last week, Dennis Hartmann, a chapter author for the fifth assessment report of the Intergovernmental Panel on Climate Change (IPCC), referred to the past 15 years as the "hiatus," a not-well-understood period during which the earth's warming has paused. Hartmann is a professor at the University of Washington, where I was his teaching assistant and colleague in the Department of Atmospheric Sciences in the 1990s. Hartmann presented his own views at the seminar, not those of the IPCC.

(The IPCC's fifth assessment report is due later this month. The last one, which said the body of participating scientists was 90 percent certain global warming was human-caused, came out in 2007.)

At the seminar, held in Seattle, Hartmann said the biggest contributor to the leveling of the global-warming trend has come from the Northern Hemisphere winter. Possible explanations, he said, were natural variability or the oceans taking up heat from the atmosphere.

"That's one of the hot topics right now in climate research," Hartmann said.

So what about the rebound of the polar ice sheet? Can we stop worrying about the polar bears?

The USA Today has what Hartmann called "a more balanced approach" than the more conservative media to the ice sheet story. This year's ice cap may be 60 percent larger than last year's at its smallest point, but it's still historically small. As the USA Today story points out, "the seven summers with the lowest amount of ice have all been in the past seven years."

"The overall trend is downward, and it will continue to do so," Mark Serreze was quoted saying in the story. Serreze is director of the National Snow and Ice Data Center.

Hartmann said in an email on Wednesday, Sept. 11, "2013 is back near the norm of the past decade.

"It is true that the sea ice minimum varies from year to year due to natural variations.  2013 did not get back to (the historic) normal, but is in the new normal post-2000."

The old, well-accepted wisdom about climate change holds true again. One cold year does not a new trend make. Let's see what happens to the polar ice cap in the next five to 10 years.

"If it gets back up to the values in the late 1990's it will be interesting," Hartmann said.

*Anthropogenic, or "human-caused" global warming