May 13, 2005

Climate Cycle or Climate Psychic?

Filed under: Climate History

In light of the general hysteria over global warming, it’s nice, once in a while, to be able to couch our current and ongoing climate changes into some larger perspective. We keep hearing about historically warm years, warm decades, or warm centuries, uncharacteristically long or severe droughts, etc. for which mankind’s striving for a high quality of life is to blame, via the internal combustion engine and its by-product, carbon dioxide. But in reality, in most cases, we have a tragically short record of good observations to really determine how much of a record we’re even close to setting.

For example, let’s take one fairly recent climate discovery called the Pacific Decadal Oscillation, or PDO. In the late 1990s, some west coast fisheries researchers noted cyclical behavior in the annual salmon harvest and tied it to a Pacific Ocean climate anomaly. It turns out that when the Pacific Ocean off of Southern California and the Baja Peninsula is warmer than normal at the water surface, temperatures are typically lower than normal in the north central Pacific well south of the Aleutians. This state, called the positive phase of the PDO, is also linked to dry conditions in the Pacific Northwest and the northern Rockies and above average rainfall in the Desert Southwest (see Figure1). In the opposite situation, negative PDO, you simply flip the sea-surface temperatures and precipitation patterns.

(Read more at Tech Central Station)




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