Climate Variability vs AGW
Emissions of CO2 from burning fossil fuel contributes significantly to a gradual increase in the world’s average temperature. What’s also known but less understood is the erratic variation in the average temperature due to cycles in the ocean, resulting in episodes of El Nino and La Nina. Some claim that these temperature extremes are well-understood as a result of changes in the trade winds, as the wind pushes the water around the Pacific ocean, exposing colder or warmer water to the surface. This may have been a perfectly acceptable explanation, except it doesn’t address what causes the wind to vary — in other words the source of the erratic wind variation is just as unknown.
So we are still left with no root cause for the ocean cycles. Apart from the strictly seasonal changes we have no explanation for the longer-term pattern of natural variation observed.
The likely key to a physical understanding rests in solving the fluid dynamics of the ocean. There are two aspects to this that have long presented an intellectual challenge. The first challenge has been to model the sloshing dynamics of a huge body of water — this typically involves numerical calculation in the form of computational fluid dynamics (CFD). The second challenge is to feed in a possible forcing and see if that can match the cyclic patterns observed. This requires a search through plausible physical mechanisms. Complicating matters is that the cycles may be chaotic so that any agreement we find would be useless from a practical standpoint, as chaotic patterns are impossible to model regardless of the source forcing.
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