Global Tropical Response to ENSO Events

UPDATE (10/06): As I have written in more recent posts, this analysis is flawed.  In fact, as I have begun to understand cirrus cloud behavior in the tropics better, I’m beginning to find this analysis unnecessary.  Soon, I will make a post that will hopefully conclude my studies on cirrus cloud in the tropics.

A component of Erl Happ’s theory of climate change, which I will eventually post on, is that El Nino and La Nino events are not internal oscillations.  He claims that these tropical warming events are caused by changes in tropical albedo, which is caused by a change in 200 hPa cirrus cloud cover, which itself is caused by changes in solar activity.

So if tropical warming events are due to an increase in the amount of UV radiation reaching the tropics, then the tropics should respond globally – not just in the Pacific.

Using regions defined as the first place that ENSO events become apparent in the Pacific, Atlantic, and Indian Oceans, I retreived Sea Surface Temperature (SST) for each of the oceans. (Source: http://nomads.ncdc.noaa.gov/.  See this post for instructions.)

Indian Ocean: Lattitude: (-5, 5) Longitude: (60, 94)

Atlantic Ocean: Latitude (-5, 3) Longitude: (-15, 5.5)

Pacific Ocean: Lattitude (-5, 5) Longitude: (-132, -82)

Once again, these are not the entire areas where El Nino/La Nina events occur in the tropics, nor are they the entire areas where heating from a decrease in tropical albedo should occur.  These are the regions that the El Nino/La Nina signal first becomes apparent in each ocean.  The point of this is not to accurately describe the tropical warming events, but to determine when they each begin.

Here is a graph of each of these regions from Jan 1978 to Aug 2007.

To more clearly see the different response times in the oceans, here is a graph of the 1997/1998 El Nino event as exhibited in the three oceanic regions that show the first response to an El Nino/La Nina event.

For this tropical warming event, the Atlantic saw a 7-month lag behind the Pacific, and the Indian Ocean saw an 8-month lag behind the Pacific.

This large lag between the Indian and the Pacific ocean appears to hold relatively well during the period 1978-2007.  However, the lag between the Atlantic and the Pacific is less clear.  In fact, since 2000 it seems that changes in the Atlantic have preceded changes in the Pacific, though the Atlantic seems to have missed the past year’s large La Nina. 

In 1982, the largest recent El Nino event occured, though its effects on temperatures were dampened by the eruption of El Chichon that same year.  In this case, the Indian Ocean saw about the same lag, though the Atlantic Ocean lagged by almost two years!

So what does this mean?  Seemingly, the Indian Ocean exhibits warming with a consistent lag time (regardless of the intensity of the El Nino/La Nina).  Does this suggest that warming in the Indian Ocean is only caused by warming in the Pacific?  Or is it still possible that changes in albedo are also impacting the sea surface temperature in the Indian Ocean, and that it merely takes longer for this warming to express itself than in the Pacific?  If so, why would this be the case?

It also seems that Atlantic Nino events do not consisently lag behind Pacific Nino events.  For smaller events, Atlantic warming might actually precede the Pacific warming.  And even if small events in the Atlantic do not actually precede small events in the Pacific, they do not lag behind.  But for larger events (like the 1982/3 El Nino, the 1997/8 El Nino, and the 2007/8 La Nina), they lag up to two years behind the Pacific.  If the Atlantic Nino is actually preceding the Pacific Nino for small events, then conventional wisdom about the cause of El Nino/La Nina events is wrong, and Erl Happ’s theory stands a chance.  Yet, with such large independent oceanic variation, it is difficult to actually say if this is actually the case.

I’ve emailed Erl Happ to give him a chance to respond to my findings.  After that I’ll post a link to our discussion on the CA forum dedicated to this subject.

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