Digital Diatribes

A presentation of data on climate and other stuff

ENSO Update – A Bounce Upward

Posted by The Diatribe Guy on June 8, 2009

The ENSO Index has been updated for May month-end, and we see a two-month average index value of 0.344.

This is the first reading that is positive since last July, but last year the positive index values barely reached above 0 for a short, two-month stay before dipping back into La Nina territory.

The new value, strangely enough, seems to have certain pro-AGW members of the blogosphere salivating about how it looks like there is a new El Nino on the way. Interestingly, the same people who wring their hands about what warming is going to do to us can’t seem to wait for higher temperatures driven by a new El Nino. They are as much as telegraphing the fact that they will use El Nino-driven elevated temperatures, should they occur, to assist in their case for the idea that CO2 is increasing temperatures. It is unfortunate that they will likely have a voice in this claim – reasonable or not – since there is no correlation between the ENSO cycles and Carbon Dioxide levels (at least that I am aware of).

In the meantime, we can look at the data to see what’s going on with the index. El Nino and La Nina have somewhat sketchy official designations, but I think it’s a fairly common rule of thumb to say that when the index reads above 0.5 for three consecutive months, we’ve got ourselves an El Nino. When the index goes below -0.5 for three consecutive months, it’s a La Nina. I have an interesting observation regarding that a little later on. Based on that rule of thumb, it looks like we’ve come out of a recent La Nina in March. The last one wasn’t particularly strong or lengthy, though it did come on the heels of a stronger one the year before.

In April, the index increased quite a bit, though the 2-month average was still negative. The May value increased again from that level. However, talk about a new El Nino, while entirely possible, is a bit premature. We’re not even at one data point that qualifies yet.

We know that both the upside and downside happens whether we’re in a cooling or warming cycle, so regardless of what side of the argument you are on, you can’t really make any wild claims about what the latest cycle means. It’s probably more accurate to assess the ENSO index over time.

I have updated the best-fit wave pattern against the available ENSO data and shown it below:


Best-fit wave pattern against ENSO data.

The best-fit cycle shows around a 60-year wave pattern. We are now entering the downside of that wave. One thing I noticed is that the best-fit requires a vertical shift upward of the wave. This means that the zero-point of the index should probably be higher than it is. The latest maximum, for example, reached a level of 0.4687 on the crest of the wave (meaning that El Nino will be elevated by nearly half a degree during that time) and the latest trough of the wave was -0.3966 (El Nino will be lowered by about 04 tenths of a degree). The index should really be calibrated down by about 0.05 of a degree. Otherwise, the significance of El Nino will be overstated while the corresponding La Nina will be understated.

The best-fit ENSO wave pattern actually has a negative linear trend that makes a longer-term extrapolation questionable. I didn’t particularly believe that element of it. It fits the current data well, but the gut-check test tells me it would be best to simply leave this parameter at zero. When I run that, the least-squares fit is only marginally worse, but the long-term, extrapolated values make a world more sense. The graph as shown is not much affected, and the same vertical effect is still shown. Just another lesson in modeling, where simpler is often superior. The chart above excludes a linear trend assumption.

According to the chart above, the cold phase of ENSO is just beginning. Yes, we will have El Ninos, but the next 25 years or so will probably look closer to the left half of the chart than the right half of the chart in terms of magnitude of the peaks in relation to a zero index value. In relation to the wave, the peaks seem to ride the wave nicely.


11 Responses to “ENSO Update – A Bounce Upward”

  1. Page48 said

    Really beautiful graph. Thanks

  2. erlhapp said

    Nice way to show that ENSO involves long waves of activity. But this exercise should also be possible using tropical sea surface temperature data that goes back further in time. It should be apparent that ENSO 3.4 is just a proxy for the global tropics which in turn drive global change.

    Shortly, when I have adequately ironed out my syntax I will post at, an explanation of how the sun drives ENSO via the QBO in the tropical stratosphere which simply reflects change in the ozone content of the stratosphere.

    The Southern Oscillation is the gorilla + elephant in the room of natural climate change. There is no need to invoke ‘greenhouse gas mumbo jumbo’.

    I agree with your suggestion that the prognosis for El Nino is mistaken. Another cooling cycle is imminent.

  3. The Diatribe Guy said

    #2: Thanks. When I have a few minutes I’ll check out your blog. Always looking for new takes on the information.

    And I also agree that this analysis can be done on other indices. In fact, I have already done so (if you click under my PDO category, you can find a similar analysis) and I’ve also deconstructed the HadCrut data to show two very evident waves in the data stream, which correspond well with the major oscillation indices.

    I plan on getting around to looking at other ocean indices in a similar fashion. Hopefully soon.

  4. The Diatribe Guy said

    Oh, I also intended to add that, just for the record, I am not necessarily saying that the prediction of an El Nino is mistaken. I simply believe it’s premature, both on whether or not one actually develops and to what magnitude/length it will be.

  5. Bob H said

    The prediction of a new El Nino brings mixed feelings. The last El Nino left us with about 6 feet of snow in 2 weeks (Three back-to-back-to-back blizzards). Drifts around our house and neighborhood were up to around 9 or 10 feet. It was good for the farmers, bad for the ranchers, and a pain to get anywhere for a few days. Everything grew well in the Spring, though.

    A sinusoidal curve makes a lot of sense, as most natural processes are very rarely linear, and often have a cyclic nature. It’ll be interesting to see where the index goes over the next few months.

  6. Bob H said

    Bad news, Joe. It looks like you may be in for a cold June. We’ll be about normal, which is to say cool for the first half of June, and warmer the last half. Hopefully NOAA will be wrong on this one. See the link.

  7. The Diatribe Guy said

    It’s already been a very cold June for us. This won’t help! I can even handle it a little cooler if the clouds break and we get some sun. Cold mixed with clouds and rain is just depressing.

    I saw on the Drudge Report last night a link to a Joe Bastardi report at Accuweather saying that some areas of the country may have a “year without a summer” if the Jet Stream stays as far south as it has. He specifically pointed to the Midwest to Northeast.

    Wonderful. Might as well make it three years in a row of below average temps.

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  9. erlhapp said

    Mr Diatribe,
    My post is up at
    Comments welcome.

  10. Carl Wolk said

    Your post makes important points, and I am always glad to see a focus on ENSO because its power is underestimated as an important driver of global climate change. When a strong El Nino event occurs (like the 86/7 or 97/8 events), it’s like throwing a monkey wrench into the climate system.
    You replied to Erl,

    “In fact, I have already done so (if you click under my PDO category, you can find a similar analysis) and I’ve also deconstructed the HadCrut data to show two very evident waves in the data stream, which correspond well with the major oscillation indices.”

    The PDO was described by Newman et al as “the integrated effect of ENSO”:

    As I show in my post which I will link to below, ENSO has driven the Atlantic Meridional Overturning Circulation (AMOC) since the climate shift of 1976, and the AMOC drives the AMO. The long-term slowing of the AMOC that occured after the 1997/8 El Nino drove a rise in the AMO.

    The PDO and the AMO (since 1976) are manifestations of ENSO; for more information and some graphs, see my latest post:

    • The Diatribe Guy said

      Thanks, Carl. I have taken a brief look at your blog. Looks like some good stuff upon an initial perusal, but it looks involved enough that I’ll need to set aside some time to go over it more closely. Thanks for sharing the link. I will make sure to check it out further.

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