Guest post by David Archibald
Bob Tisdale’s post on ENSO on 19th November prompted me to see what I could find in the Southern Oscillation Index (SOI) data. The SOI is calculated from the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin. Sustained negative values of the SOI often indicate El Nino episodes. These negative values are usually accompanied by sustained warming of the central and eastern tropical Pacific Ocean, a decrease in the Pacific Trade Winds, and a reduction in rainfall over eastern and northern Australia. Following is a graph of the SOI on a monthly basis from 1876 to 2010. The major El Ninos are discernable, otherwise it looks like a lot of noise.
The graph following shows the cumulative monthly SOI from 1876 to 2010.
The SOI does tell a story. It was non-trending for the last of the Little Ice Age and then from 1920 went into a long La Nina-dominated trend that ended with the Great Pacific Climate Shift of 1976. The planet warmed into the 1930s at the beginning of this trend, but then cooled, as it should have down in a La Nina-dominated trend, from the 1940s to the 1970s.
The subsequent El Nino-dominated trend from 1976 to 1995 was almost three times as fast as the rise. The Climategate emails show that Phil Jones was aware that global warming ended in 1995. The end of the El Nino-dominated trend in 1995 might be the physical cause of that cessation of warming. The SOI has been non-trending since.
This might have been a very neat story if the world had cooled instead of warmed into the 1930s. The 20 years of El Nino-dominant trend from 1976 to 1995 produced the late 20th century warming that got so many people hot and bothered. The story told by the SOI also reinforces how important the Great Pacific Climate Shift of 1976 was. The climate system turned on a dime for some as yet unknown reason.
The great Pacific Shift happened at the same time that the Atlantic also started it’s warm phase. I am at a loss as to why the Pacific and Atlantic seem to cycle together, but the changes in both seem to happen at the same time.
Whatever is causing both Oceans to cycle in this manner is what is causing the sawtooth in the global temperatures. That is the 1-2C variation each couple hundred years. We are near a peak of that activity and a drop-off will happen in the next 10-15 years, but the question is why?
John Kehr
John Kehr says:
December 9, 2010 at 4:00 am
Could be they cycle together due to the interconnected thermohaline circulation I mentioned in my post at 3:56am
How is the “monthly cumulative” calculated?
I don’t think there is a physical explanation which allows an accumulation index for the ENSO.
The high resolution daily/weekly/monthly data shows that the ENSO has a continuous on-going impact on the climate which lags behind it by 2 to 4 months.
There is also a smaller lag of about 8 months as the warm/cool ENSO waters circulate into other ocean cycles/areas like Kuroshio and the Indian Ocean. Atmospheric circulation patterns will then leave a secondary footprint in other major ocean cycles like the AMO (the AMO peaked in August and is now falling rapidly – down 0.3C in the last 3 months). Since the Atlantic and the Pacific are separated by land, atmospheric circulation is the only way the ENSO can impact the AMO (and landmasses in general I guess).
After that, the ENSO’s impact is lost to the climate. It is lost to space. It doesn’t hang around for 20 years. The real climate does not operate like that.
So, today’s climate is always being impacted by the La Nina of 3 months ago (and there is a smaller secondary lag of about 8 months which doesn’t always show up but does about 50% of the time). These lag timelines will explain a large amount of the general climate fluctuations.
There are at least 5 major climate indices that show this pattern including temperatures, water vapour, cloudiness, outgoing longwave radiation and rainfall. So, the physical explanation for the lag timelines is evident in the climate indices themselves.
Dr.Archibald: In the first graph, above: SOI 1876- 2010; at the X axis: 1876 -2007.
Which one is it OK?
Tenuc says:
December 9, 2010 at 1:32 am
You are right. See graph on page 50:
ftp://ftp.fao.org/docrep/fao/005/y2787e/y2787e08.pdf
vukcevic says:
December 9, 2010 at 3:58 am
What do you mean by Gateway? You indicate latitude but not longitude (not all of us are “initiates” in the Opus Magna 🙂 ). BTW, your following graph take us closer to the cause of these changes (was it the Sun, again?)
http://www.vukcevic.talktalk.net/LFC20.htm
David,
My cumulative chart peaks in June 1976 (+680) with a double bottom(?) May 1998 (-485) and May 2007 (-487).
Checking the BOM data you linked to I see that they are similar,but different, to the BOM SOI data I used 3 or so years ago.
Any idea how many versions of SOI data BOM have?
Are they subject to revision?
Any use of Australian weather patterns should certainly mention of the Indian Ocean Dipole. It’s certainly likely that neighboring cycles can reniforce or mitigate each other’s effects in boundary areas. For some info on the IOD / Aussie drought correlation see the following short article:
http://www.science.unsw.edu.au/news/indian-ocean-drought/
Reminds me a bit of when I did a 6 year smoothing (I chose 6 years because it was the difference in time between the big dip in 1991 and the big El Nino in 97/98) of the Oulu neutron monitor. I noticed in that chart that the El Nino’s seemed to arrive durring the ramp up to max, not on a peak, much like what you were describing above.
crosspatch says:
December 9, 2010 at 1:57 am
“It was non-trending for the last of the Little Ice Age and then from 1920 went into a long La Nina-dominated trend ”
“Please keep in mind that during a La Nina phase, the ocean is actually absorbing heat. So while the surface temperature is lower because of the stronger trade winds, the reduced cloud cover is actually allowing more solar radiation to reach the water.”
Excellent to remember. Many times I hear the statement, “the planet warmed, or the planet cooled, when all that is known, or factual would be, the atmosphere warmed or cooled.
It would be interesting to see the cumulated SOI plottet with the AO, AAO and the NAO. Maybe a more complete story would begin to emerge..
“clear as mud”
That’s your point of embarcation. Return to basics: SO is Gaia’s heat sink, NH her radiator fins. Solar input runs on(from our vantage point) a 400 year cycle of activity. As earth heats, atmospheric H2O rises increasing albedo. Earth is turning off Solar input just as that input drops.
Thanks for another salient addition to the puzzle, Mr. Archibald.
David Archibald wrote: “No, I don’t believe in big lags in the atmospheric climate, so the warming of the 1920s and early 30s may have been due to another factor – the Sun did become more active.”
The difference between your cumulative SOI graph and the variations in global temperature could and should also suggest that the sea level pressure difference between two points in the Southern Hemisphere does not represent the effects of ENSO on global temperatures. And that’s because the SLP at those two points are also impacted by processes that aren’t related to ENSO.
It could and should also suggest that there may be problems with the early SOI data. SOI data is made up of two Tahiti SLP datasets, before and after 1935. The pre-1935 Tahiti SLP data was “discovered” in the late 1980s. It was incomplete, like many datasets. And those problems have to be understood and presented.
Again, if we use NINO3.4 SST anomalies and not SOI data, we can use period average NINO3.4 SST anomalies to show that global temperatures rose while El Nino events outweighed La Nina events and that global temperature dropped when La Nina events dominated.
http://i56.tinypic.com/zxmsg8.jpg
That graph is from this post:
http://bobtisdale.blogspot.com/2010/11/multidecadal-changes-in-sea-surface_17.html
Regards
crosspatch says:
December 9, 2010 at 1:57 am
Indeed, remembering that the oceans have 3000 times the heat capacity of the atmosphere, global temps, whether measured at the surface or near the tropopause are just noise.
I’d bet a differential equation presenting evolved heat would output something approaching the cumulative SOI.
“”Panama Canal Shut – Rain” It was the first time in 100 years that the passage had been closed.
http://chiefio.wordpress.com/2010/12/08/panama-canal-shut-rain/#comment-9767
It seems that this La Niña has become quite an aggressive “Lady”: “The Lady of the Rains”
Bill Illis says: “I don’t think there is a physical explanation which allows an accumulation index for the ENSO.”
Somewhat along those lines, I don’t believe there’s an ENSO index that captures the true effects of ENSO. None capture the release of warm water from below the surface of the PWP and the redistribution of that warm water after the El Nino has ended. None capture the increase in Downward Shortwave Radiation over the Pacific Warm Pool during an El Nino, which helps to supplement the El Nino and recharge the PWP. None capture the increase in precipitation over the PWP during a La Nina, with the increase in precipitation indicating of an increase in heat released into the atmosphere. Etc.
John Kehr says: The great Pacific Shift happened at the same time that the Atlantic also started it’s warm phase. I am at a loss as to why the Pacific and Atlantic seem to cycle together, but the changes in both seem to happen at the same time.
Whatever is causing both Oceans to cycle in this manner is what is causing the sawtooth in the global temperatures. That is the 1-2C variation each couple hundred years. We are near a peak of that activity and a drop-off will happen in the next 10-15 years, but the question is why?
Then we have:
Baa Humbug says:
Could be they cycle together due to the interconnected thermohaline circulation I mentioned in my post at 3:56am
YES!
See: http://mason.gmu.edu/~bklinger/drake.pdf
Which talks about the Drake’s Passage effect and how it drives the circulation of the ocean currents. (The circulation is NOT just an artifact of salty cold sinking).
Then these two point out oscillations of many years span in the circumpolar current.
http://oceancurrents.rsmas.miami.edu/southern/antarctic-cp.html
http://www.nature.com/nature/journal/v380/n6576/abs/380699a0.html
Put them together and you get periodic oscillations of the circumpolar current and winds that would cause oscillations of the overturning current that would drive La Nina / El Nino on a short term as well as possibly influencing the strength of the Gulf Stream and temperatures in Europe.
(No, I’ve no proof for this conjecture as I’ve just made the connection… but the pattern “fits” and is worth a “dig here”…)
Moderator-
In the sentence containing “as it should have down in a La Nina-dominated trend”, please change “down” to “done”.
You may delete this message.
IanM
It is my understanding that it is the Trade Winds that blow the warm surface water westward during a La Nina, permitting the cold subsurface water to rise.
IanM
******
At December 9, 2010 at 3:56 am Baa Humbug said:
I find it interesting that El Ninos almost always have a stronger influence on global weather patterns than La Ninas.
I also think that if ENSO was a product of TSI or cloud cover, long term ENSO predictions would have been more accurate than they are now.
The “usual” conditions in the pacific is for the waters in the eastern pacific, near Peru, to be generally 8DegC COOLER than it’s latitudinal position would indicate. This is because of the cold ocean currents flowing up the coast of Chile, upwelling near Peru.
When this upwelling slows, the surface waters warm quickly = EL Nino. The more dramatic this slowing, the stronger the El Nino. It’s effects are well known, floods in South America, droughts in Australia and North America and an increase in global temperatures.
When the upwelling speeds up, the surface waters cool back down, higher than normal speed = La Nina
The upwelling is the result of the thermohaline circulation, a phenomenon we know little about. I recall reading somewhere that there were many sensors released recently into the oceans to track the thermohaline circulation. If and when we get a handle on what makes this circulation tick, we’ll be able to predict ENSO events quite accurately.
Caveat: Though solar insolation or cloud cover do not cause ENSO events, they may well modulate the strength of these events. High insolation during El Nino strengthens it, low insolation weakens it. Vice versa for la Nina.
These are what I accept regarding ENSO events. I got my information from the web site of the late John L Daly HERE and HERE and many many other articles John posted about ENSO
regards
I am not certain how Dr Archibald calculated his cumulative graph. I can see that it does not make sense in temperature terms to accumulate value over period of 20 years.
However, if there is a spiky (noise like signal) than a 20 year moving average (running mean), makes sense. If during the process the sum is retained without dividing by 20 (for 20y m.a.) then you would get a cumulative or 20 year integrated output.
This helps to visually identify likely source of the variable, which may not be otherwise so obvious.
To many this may not make much sense, but Dr. Archibald’s graph, in my view, is one of more important recent publication at the WUWT.
Now it is possible to identify the source and cause of the Southern Oscillation.
http://www.vukcevic.talktalk.net/NPG.htm
I have also included the PDO graph, which I mentioned in a post on Dr. Curry’s ‘Climate etc’ blog; her commenthere
E.M.Smith says:
December 9, 2010 at 7:10 am
Thnx for those links EM, I’ve added to my collection.
E.M.Smith says: “YES!” in response to Baa Humbug’s question, “Could be they cycle together due to the interconnected thermohaline circulation I mentioned in my post at 3:56am”
How? There’s a time lag (a couple of years at minimum) between the release of heat from the Pacific Warm Pool until the time that any residual warm water could be carried down to the ACC, then caught up into the Benguela Current in the South Atlantic, and carried north into the North Atlantic. If memory serves me well, an ENSO signal takes 8 years to travel around the Antarctic in the ACC.
Through teleconnections or atmospheric bridges an El Nino event will impact the North Atlantic in a few months. Or in the case of the 1976 Climate Shift, it would be the transition from a 3-year La Nina that ended early in 1976 to a minor El Nino in 1976/77, and that drastic change may have initiated the change in the North Atlantic.
@wilt December 9, 2010 at 12:31 am:
As far as that goes, has anyone ever figured out what is the CAUSE of the El Niño itself? Everyone seems to look at it as a cause in and of itself.
Yes, the central and eastern Pacific SST rises. Yes, to all the things we observe.
But what is the underlying cause?
Please don’t anyone tell me it is because the winds changed. That doesn’t account for the addition heat energy. And even with the winds changed, what are the arguments that it isn’t itself just an effect?
So, that additional heat – where does it come from?
I’ve looked all over the place and haven’t found a decent explanation – or even much of an effort – to find out where that comes from.
El Niño is not an underlying cause. It is an effect itself.
@John A says December 9, 2010 at 1:36 am:
John –
I scratched my head about that, myself.
Try this:
In the article David Archibald talks about the SOI going negative sometimes (and I assume positive at other times). I read that to mean that it all starts from a baseline of zero and negative values deduct from the cumulative SOI, and positive ones add to it. I would suppose Archibald means that – looked at long enough – the overall cumulative total should end up at or near zero.
That would also imply that – in that long, long term – half the curve would be below zero and half above zero. That doesn’t seem to be the case during the interval of the chart, and that may mean that a negative trend may occur at any time in the next several decades. (But perhaps the starting point was at a low point.)
For some reason, this graph – and that Great Climate Change of 1976 – makes me think of James Hansen in the 1970s and his prognosis that warming was on its way. All I remember from that winter of 1976-1977 was how utterly arctic the U.S. was. It was a year I moved out to the boonies, and it cured me of ever wanting to do that again.
But Hansen may have noticed something that he has kept mum on all these years, something that told him a reversal of the cooling trend was imminent. That may be giving him more credit that he is due, but the thought did occur to me.