There has been a bit of noise among critics of global warming over a report from NASA announcing:
A cool-water anomaly known as La Niña occupied the tropical Pacific Ocean throughout 2007 and early 2008. In April 2008, scientists at NASA’s Jet Propulsion Laboratory announced that while the La Niña was weakening, the Pacific Decadal Oscillation—a larger-scale, slower-cycling ocean pattern—had shifted to its cool phase. [...]
Unlike El Niño and La Niña, which may occur every 3 to 7 years and last from 6 to 18 months, the PDO can remain in the same phase for 20 to 30 years. The shift in the PDO can have significant implications for global climate, affecting Pacific and Atlantic hurricane activity, droughts and flooding around the Pacific basin, the productivity of marine ecosystems, and global land temperature patterns. “This multi-year Pacific Decadal Oscillation ‘cool’ trend can intensify La Niña or diminish El Niño impacts around the Pacific basin,” said Bill Patzert, an oceanographer and climatologist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “The persistence of this large-scale pattern [in 2008] tells us there is much more than an isolated La Niña occurring in the Pacific Ocean.”
Natural, large-scale climate patterns like the PDO and El Niño-La Niña are superimposed on global warming caused by increasing concentrations of greenhouse gases and landscape changes like deforestation. According to Josh Willis, JPL oceanographer and climate scientist, “These natural climate phenomena can sometimes hide global warming caused by human activities. Or they can have the opposite effect of accentuating it.”
The emphasis is mine. While the anti-global-warming camp seems to be gleefully focusing on expectations of a cyclical cool-down, I can’t help but feel a little satisfied over how the the emphasized text supports my own personal belief — that if human-driven global warming is occurring, it is all but impossible for casual observers like you or I to identify, amidst the noise of longer term weather cycles which we might not fully understand.
Or in English — I can believe that “global warming” is happening, but the climatological anomalies the pro-warming crowd hypes are probably noise or the impact of timing in normal cyclical processes.
That isn’t to say that climate changes aren’t worrisome, and shouldn’t be planned for. Research and reasonable measures to reduce the harm to society…or at least to prepare for the risk, are probably wise steps to take.
Similarly, many of the conservation / pro-environment initiatives that have been proposed, in the name of combating global warming, seem to be good ideas without the perceived crisis of imminent global climatological disaster fueling their consideration.
I just worry that when the hyped changes fail to manifest, and normal cycles reverse, there will be a backlash from a mislead public, which will derail efforts which have value on other merits.
For example, consider the following chart which appeared at “Watts Up With That?”, taken from a paper on the PDO by Professor Easterbrook, retired from Western Washington University:
The blog post includes an addendum from Professor Easterbrook, who observes:
The projected warming from ~2040 to ~2070 is NOT driven by CO2, it’s merely a continuation of warm/cool cycles over the past 500 years, long before man-made CO2 could have been a factor. We’ve been warming up from the Little Ice Age at rate of about 1 degree or so per century and the 2040-70 projection is simply a continuation of non-AGW cycles.
That further supports my suspicion that we’re noticing cycles-upon-cycles…and even if humans weren’t influencing climate, there might be a reason to plan for a warmer world.
On the other hand, the Maunder Minimum folks happily note that Sunspot Cycle 24 still hasn’t really kicked off…
