So, the theory is this: When it’s hot and the trade wins are a’blowin’, there’s more evaporation over vast areas of ocean. Evaporation increases the salinity of sea water, and such saltier water is heavier than the less saltier water under it, and so sinks. Cold water comes up, warm water goes down. The cold water, in turn, is now ready to get warmed up, pulling heat energy out of the atmosphere. Thus, the overall heat content of the atmosphere is decreased, and the overall heat content of the deep oceans is increased.
(Warmer water is also less dense than colder water until you get real close to freezing, so that warmer water typically floats on top of cooler water – so, the theory is, as so often the case, not quite so simple: the increase in weight per volume caused by increasing salinity needs to be greater than the decrease in weight per volume of the warmer, expanding water. Maybe that was in a footnote somewhere.)
I read this little article looking for the place where they’d say something like this:
“This newly discovered cycle means that not only are current global atmospheric temperatures lower than what might otherwise be expected during this approximately 35 year long periods of greater than usual tradewind activity and evaporation, temperatures over the preceding 35 years of low activity, which corresponds nicely to the timeframe on which the ‘hockey stick’ model projections were based, were warmer than should otherwise have been expected. Thus, the slope of the curve projecting increasing temperatures needs to be reduced by approximately half, meaning that any effect from warming will likely not be felt for many years further out than was previously projected. Scientists issued a statement saying, “Whoops! Sorry about that!” and asked not to be bothered while they reworked their models to incorporate this new bit of information.”
I was disappointed.
Here’s an overview, which was left out of the article except by the inclusion of the above map, which is more confusing than helpful. You’ve got these existing currents, for example, the Gulf Current. The tropical sun beats down on the Gulf of Mexico and the Caribbean, heating up the water, which, after the manner of liquids, expands and spreads out. The only direction the water can flow is out into the Atlantic – every other direction is blocked. This warm water floating on top of the colder, deeper water, flows up the Atlantic, warming the Eastern Seaboard, England, and eventually Norway. Eventually, these Caribbean waters cool and sink in the Arctic, where they are replaced and overshot by incoming Gulf water. Way down deep, cold water is flowing in the opposite direction: Arctic water deep in the ocean flows south into the Caribbean.
All this is very very good, in that it stirs up nutrients for plankton blooms, makes England a green and pleasant land, and makes Scandinavia inhabitable. Other currents behave in similar ways for similar reasons. We in California do not get a warm current from the south, we get the cold water from the Gulf of Alaska. Que sera sera. The overall effect is to warm the cool places, cool the warm places, and give the fish of the sea something to eat. It is a thing of beauty.
This new theory is that, on top of the normal currents, there’s another heat exchange mechanism at work. Why it cycles is anybody’s guess at this point – a 70 year period doesn’t correspond to anything I’m aware of. At any rate, saving the appearances demands that such a cycle exist – and it certainly could. But I’m not sure the fans of AGW are noticing that every time a new discovery is made that saves the appearances, it weakens the case that we know enough about the climate to predict much, let alone influence it. Hard as it is to grasp, there are things that are simply too large or complex or both for human beings to do much about, even if (unlikely) we possessed the wisdom to know what we ought to do.