by Doug O'Harra
Anchorage Daily News
February 04, 2005
"I think there's an anthropogenic (human-caused) part to what's going on, but at least as large in my view is the natural variability," Walsh says. "For that reason, I would hesitate to predict that the next 30 years will see a warming comparable to the last 30 years."
Walsh is the chief scientist at the International Arctic Research Center at the University of Alaska Fairbanks. He teaches science to college students and regularly cranks up Alaska's supercomputer to calculate future climate scenarios.
Walsh helped write the Arctic Climate Impact Assessment for the international Arctic Council, to be released later this year. He presented a summary of the report at the Marine Science in Alaska conference recently in Anchorage and spoke to the Anchorage Daily News about climate change.
Q. What is the most dramatic evidence of climate change in Alaska?
A. The most dramatic I would have to say is the sea ice distribution. The last three or four summers we've had ice really unprecedented distances offshore north of Alaska. And the past few winters we've had very little ice in the Bering Sea, and this winter is following the pattern very well. There's not much ice out there.
I think the one other area I find impressive in Alaska is the glacier wastage that's been studied by the glaciologists. Alaska's loss of glacial ice over the past several decades is actually larger than anywhere else, in terms of contribution of water to sea level.
There's even more fresh water being lost from Alaska glaciers than Greenland. And the photographs tell the story. There is some very impressive evidence there.
Q. Are we losing sea ice because of changing air temperatures, or because of changes in ocean currents?
A. That's a really good question. It may be the temperatures, it may also be the wind, and it may also be the ocean current bringing more heat in from the Atlantic, and from the Pacific as well. And I don't think there are real good answers.
What does seem clear is that in the early 1990s, actually '90 to '92, there were a few years of wind patterns that did push most of the thick ice away from where it had been found for decades. In a sense, the Arctic Ocean did not recover from those few years, even though the winds have (since) returned to more normal pattern. So my hunch is that winds are at least part of the story.
The oceanography also seems to be finding indications of an inflow of warm water below the surface of the sea ice from the Atlantic Ocean. ... So that's another push toward less ice.
Q. Given all this, is there any doubt that climate change is well under way?
A. There are skeptics, and there are skeptics at a couple of levels. Even if we all agree that there's change going on, there will still be debate as to whether it's anthropogenically driven - greenhouse-gas driven - or whether it's attributed to natural variation or some other factor.
There's even some who'd argue that we're just seeing ups and downs, cycles so to speak, that are part of natural variability and that we aren't experiencing a trend.
Now the proponents of that argument are becoming fewer and farther between as time goes on. But even when the (public overview of the Arctic Climate Impact Assessment) came out back in November, there was some reaction by some of what I'd call conservative science groups saying that (the report) was overplaying the trend itself and that it was overplaying the human attribution.
Q. Do we know what would be happening to the climate if people stopped releasing greenhouse gases?
A. When they run (supercomputer) models without the greenhouse gases, without the global greenhouse gases increasing, there are ups and downs that last for a decade or two _ in temperature and several of the other variables. And these ups and downs do tend to be larger in the Arctic than they are in the global average. So these swings _ the ups and downs that last a decade or two _ are apparently part of the natural climate system.
Q. So people should understand that the role played by greenhouse gases in recent climate change is not settled yet?
Q. And it's still not absolutely clear that we're launched on a permanent warming trend?
A. Right. There are going to be bumps in the road along the way. Actually the analogy that I heard that I think is very good is the analogy to the stock market in a bull market situation. The market may be going up, but along the way there are ups and downs, there are corrections.