Excerpt:
Superimposed on the alternation of La Niña and El Niño are longer term variations in the frequency and intensity of El Niño and La Niña. A period of more frequent and intense La Niña between the mid forties and 1975 followed by more frequent and intense El Niño between 1976 and 1998. The pattern appears in centuries of proxy data - that is in tree and coral rings, sedimentation and rainfall and flood records.
Global surface temperatures have a similar trajectory. Falling from 1946 to 1975, rising between 1976 and 1998 and declining since.
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ENSO variation goes in both directions. The indications are that ENSO variation added to global surface temperatures between 1976 and 1998. It has been almost 10 years since temperatures peaked in 1998. The planet may continue to be cooler over the next few decades as a cool La Niña phase of ENSO emerges.
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I am a bit sceptical of this CO2 hypothesis. Simple, easy to grasp, goes down readily with the masses but at 0.04% just work out how many molecules per thousand that represents. Then, add salt to your porridge in that ratio and see if you can taste it.
The aa index of geomagnetic activity is closely linked to solar forcing of temperature at the surface of the Earth. Jerks in the aa index are inversely associated with movements in the SOI index. La Nina type cooling and El Nino type warming across the entirety of tropical latitudes is driven by the solar wind apparently interacting with the ionosphere and the neutral atmosphere in such a way as to affect the amount of solar radiation that runs the gauntlet of the atmosphere to warm the tropical oceans. Some appreciation of plasma physics is required. Understand the physics and the mechanism becomes very clear.
The variation in warming of tropical latitudes is clearly associated with temperature fluctuations at high latitudes in the northern hemisphere, especially north of about 60°N latitude. The medium of thermal exchange is ocean currents. Much of the water that is warmed north of 30°south latitude ends up circulating in the northern hemisphere.
El Nino activity has dominated the last three cycles while La Nina activity will dominate the next three just as it did in the period between 1945 and 1976.
Furthermore, it appears that the increase in the aa index over the last 120 years or more is associated with an increase in the poloidal field of the sun driving both sunspot activity and the coronal ejections that we know as the solar wind. This increase ended with solar cycle 19. The poloidal magnetic field of the sun has been in decline over the last three solar cycles. We are currently experiencing very low sunspot activity but solar cycle 24 may yet be 18 months away. Over this next 18 months we should see a very intense La Nina. The end of nine of the last 12 solar cycles has been marked by La Nina and the early stage of the upswing has been marked by El Nino on 9 of 12 occasions. These events are clearly associated with the collapse and subsequent recovery of the aa index of geomagnetic activity at solar minimum.
There is no apparent association between sunspot activity and temperature. Sunspot minimum is marked by cooling followed by warming over the space of about three years at solar minimum. Sunspot maximum is frequently marked by La Nina cooling if a collapse in the aa index occurs at that time but is just as likely to be marked by El Nino warming or have no trend either way.
The association is clearly between the solar wind and temperature via the agency of changing levels of solar radiation impinging on low latitudes. Generalising, there is an atmospheric window that is largely cloud free defined by the extent of the Hadley cell and the surface area occupied by the subtropical high pressure cells that returns air that ascends at the inter-tropical -convergence back to the surface. Depending upon the height of the tropopause this air is de-humidified to a variable extent, influencing upper atmospheric humidity. Some other simple mechanisms assist the phenomenon like changes in atmospheric density and the degree of ionisation of the atmosphere over the tropics.
For this exposition email erlathapps.com.au
Best regards Erl
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