an impermanent travelogue
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October 07, 2003
Uphill, Both WaysA Nature Science Update feature article Alaska's climate: Too hot to handle explores the consequences and possible causes of a 2-3 °C winter temperatures increase in the past 30 years, more than anywhere else and 2 or 3 times world average.
... the spruce bark beetle, which over the past 15 years has killed more trees in Alaska than any other insect in North America's recorded history. In the Kenai Peninsula on Alaska's southern coast, some 40 million spruce have perished across an area twice the size of Yellowstone National Park. The beetle's population rocketed thanks to changes in the weather, argues Ed Berg, an ecologist with the Kenai National Wildlife Refuge. "We had a really long run of warm summers," he says.There are many other consequences of warming in a place where life, including human life, is cold adapted.
What everyone wants to know is why? Why is warming so great and why is it happening here and now? Nobody knows but great effort is being expended to search for answers.
It is ... hard to tell how much of Alaska's climate change is due to global warming and how much to natural climate cycles. The Pacific Decadal Oscillation - an El Niño-like fluctuation of temperatures between the north and tropical Pacific that takes place over 20-30 years - flipped Alaska into a warming phase in the 1970s. The North Atlantic Oscillation has also contributed to warmer winters in Alaska since the late 1960s. But at the same time it has been associated with a 2-3 °C cooling just across the continent in Greenland. There seems to be a 60-year see-saw in temperatures between the east and west of this part of the Arctic: when one side heats up, the other cools down. In a few years, this could flip again and reverse Alaska's recent warming trend. No one yet knows.Though the article genuflects to the IPCC and global warming fever it notes the many other influences such as the PDO, NAO, and AO which bring cyclical changes to local weather, some areas warming while others cool. These cyclical oscillations each occur on a different period, sometimes in phase and sometimes out of phase, so that their combined effects are irregular and can be great when they happen to coincide. The article also notes the current low state of capability in climate models and how they are based on widely different sets of assumptions. To a politician, journalist or ideologue eager for easy and clear answers this might be frustrating, but to scientists it's a box of toys begging for playmates.
The PDO changed phases in the late 1990s for the first time in nearly 30 years, corresponding exactly with the current Alaskan warming period. The next 30 years should be colder in Alaska but the PDO has many other effects. Weather all along the west coast of the Americas is affected by this oscillation. Further south along the coast of S. America waters are warmer. This not only affects weather but also sea currents and upwellings which nourish sea life. The effects of ENSO, the shorter period oscillation popularly called El Nino/La Nina, are altered. Warm periods are even warmer and cool periods are less cool.
Much of the western US is greatly affected by the PDO. The current phase of the PDO which brings cold waters to Alaska correlates with multi-decadal drought periods in the plains states, especially the Colorado plateau. Much of California, Oregon and Washington states face the same prospect. Like S. America those areas are also affected by ENSO but being farther north both the PDO and ENSO have different characteristics than in the south. Though we don't have clear understandings of the various oscillations it seems reasonable to expect significant change in the coming decades compared to the previous decades. A 30 year oscillation period is hard for a human to study or comprehend personally. People who have lived long lives close to the land and weather tell stories of how different things were in their youths (..uphill, both ways...) and are laughed at by younger people for telling tall tales. But sometimes they are just recounting observations of long cycle oscillations. I've been listening more closely to grizzled old farmers these days since the PDO flipped.