The IPCC has use many models to try to predict future global temperatures. To date, these models have done a lousy job, not even being able to predict the past climate fluctuations. Worst of all, the IPCC and the rest of the CAGW Alarmism industry have ignored the numerous natural variation explanations.
One of these lines of thought is ENSO – the El Nino/Southern Oscillation. Let’s look briefly at each of the parts.
The Pacific Ocean is huge, covering 30% of the earth’s surface. In the equatorial Pacific, where the angle of the earth’s surface to the sun is most head on, much more heat from the sun is absorbed than further from the equator. East to west the Pacific is over 10,000 miles!
Heated air rises, cooler air falls, the earth spins, and other effects work to set up easterly Trade Winds near the equator (and prevailing westerlies in temperate latitudes).
The easterly Trade Winds push on the surface of the Pacific, causing the surface equatorial Pacific water also to move from east to west. The warmed surface waters mov e to the west, while the warmed water already in the western Pacific is kept there by the Trade winds, forming a slightly elevated Pacific Warm Pool (from south of India to northeast of Australia). The longer this goes on, the deeper the warm water is pushed in the warm pool.
With the surface water moving east to west, deeper water moves west to east. This subsurface warm water may travel all the way to the eastern Pacific before it rises. Every 5-10 years, enough of this warmer, deeper water crosses to the east Pacific, surfaces, and raises the surface temperature (SST). This water movement is what makes up the El Nino.
The air over the eastern Pacific surface warms more than usual, setting up the possibility of a reversal of the wind to a west to east flow. If it happens, a west to east wind will push surface water to the east, and the previously elevated western Pacific Warm Pool may “slosh” across the Pacific, releasing much of the warm, deep, Warm Pool water. As this massive amount of warm water floods out along the whole surface of the Pacific from below the surface in the west, the average SST rises, affecting temperatures even into the Atlantic. The atmospheric effects are the atmospheric component of the ENSO.
This anomalous wind, temperature, and water movement pattern is what makes up an ENSO event. It is a fairly quick, strong, naturally occurring pattern that has happened over and over again. (It has been called other names, for example the Santa Ana wind. The song, “They Call the Wind Maria” is about an ENSO.)
After the slosh to the east, just like in a huge bathtub, the water sloshes back to the west, much of it eventually going into the North & South Pacific, and into the Indian Ocean. (El Nino usually is short lived, lasting several months, although it occasionally may resume during a seasonal period the following year.)
When the El Nino ends, eventually more normal patterns develop, called La Nina, but it may take many years to re-charge the Pacific Warm Pool and for surface water temperatures (and atmospheric temperatures) to cool back down. La Nina is slow, with the effects spread out over several years.
To make things even more interesting, there is a PDO, which may cycle over 60 years, giving 30 years of conditions more favorable to an El Nino developing and 30 years when conditions favor La Nina. The time from the mid 70s (after the last cold snap) until around 2000 was a time which the PDO favored El Nino and warmer temperatures. The last 15 years or so (and expected to continue another 15 years) is a time when the PDO favors La Nina and cooler temperatures.
Bob Tisdale has written an Ebook, The Manmade Global Warming Challenge, which shows how the big patterns of up and down global temperatures can be explained by ENSO. Please take a look.
The bottom line is, you don’t need lunatic theories, based on faulty models and a lot of ad hominem attacks, rather than actual data, to explain why global temperatures have cycled through a relatively small range, with generally beneficial results for the human race.