Here is my contribution to the speculation in relation to where ENSO is going. (and its temperature effects in the PDO, NAO and so on, involving oscillations to the nth degree).
My reasoning goes like this:
1. 200hPa temperature is driven by ultraviolet light intensity that responds to solar cycle influences including the solar wind. See the top two graphs below. Anyone who maintains that 200hPa temperature is driven by surface conditions has not looked at the data. Perhaps they don’t want to look because they might have to give up some cherished beliefs.
2. The driest air with the greatest ozone content is located in the low latitudes of the southern hemisphere in the rain shadow zones of the major continents and in the high pressure cells that are the southern leg of the Hadley Cell. Here the reaction to UV light is greatest as ozone reacts to UVB in the upper half of the troposphere. As the air is heated its relative humidity falls and the cirrus cloud disappears enabling more sunlight to stream through to the ocean. This initiates a tropical warming event. In other words the ocean absorbs energy. Lots of it. This will eventually show up as very warm water at the inter-tropical convergence zone (ITCZ) about 10°N of the Equator. The southern tropics is particularly susceptible to cloud loss from April onwards as the northern hemisphere heats up influencing atmospheric humidity from about 20° south all the way to the Arctic.
3. High cloud reflects solar radiation. It is composed of multi branching ice crystal filaments. Low cloud is composed of liquid droplets. Low cloud is much denser and tends to absorb solar radiation. Hence cloud top temperature is warmer in low cloud. Low cloud is below 825hPa. High cloud is is above 500hPa all the way to the tropopause and beyond. At high altitude any light deflection at all will increase interception rates and reduce surface flux. That is simple geometry.
All the graphs relate to 10°S to 20°S latitude.
Notice in particular the transition from 1997 to 1998 in the lower of the four diagrams. You can see that 1997 was a La Nina year until April when 200hPa temperatures jumped. The start of solar cycle 23 was May 1996. So the transition to El Nino warming in this case was 11 months. The end of solar cycle 23 has been calculated by Leif Svalgaard as July of 2008.
2007 was an El Nino year at 200hPa until June. In 2008 200hPa temperatures have been very cold from January through to August and the Southern Hemisphere has been well chilled.
Looking at the last 12 solar cycles the average delay between an upturn in sunspot numbers and a swing towards El Nino warming, not a peak, just a turning point as reflected in the annual SOI index, not the monthly index, is just over 6 months.
Solar cycle 24 may be a special case because of the weakness of the actual sunspots as described by Livingstone and Penn. Perhaps the X Ray flux will be less. In that case we might see a slower transition to weaker warming conditions than previously experienced.
Meanwhile, its November and this part of the world (south west Western Australia) is very cold.
The relationship between the SOI index and 200hPa temperature is very close as can be seen in the graph below.
Why has it taken so long for the ocean to warm up since the atmospheric window opened up in 1978? I guess the answer to that question relates to the size of the window, how long it stays open and the bulk of the material that has to be warmed. The oceans of the world are the great store of energy. The atmosphere can not store energy. It is mere ‘ether’.
The long sought link between the sun and terrestrial temperature is hereby established. More detail will follow in due course. It’s hard work.
By the way, the arrows in the diagram below summarize the primary forces involved as dictated by the Sun. This broadly reflects change in the solar wind and the strength of short wave radiation.
All data from http://www.cdc.noaa.gov/cgi-bin/Timeseries/timeseries1.pl Kalnay, E. and Coauthors, 1996: The NCEP/NCAR Reanalysis 40-year Project. Bull. Amer. Meteor. Soc., 77, 437-471.