Digital Diatribes

A presentation of data on climate and other stuff

Uh Oh… Does the plummetting ENSO Index portend a cold winter?

Posted by The Diatribe Guy on July 10, 2010

We’ve had a wetter than average summer, but the temperatures here have been glorious. Out East, they have been scorching temps as of late, and a lot of people are making a lot of hay about that (I’ve never really understood that expression).

Global temperatures have been warmer. It is what it is. No use pretending otherwise.

But this wasn’t completely unexpected. In fact, as a resident skeptic, I personally suggested prior to last winter that we’d have mild one. It isn’t rocket science. The ENSO index was into persistent El Nino territory and that was that. My prediction turned out to be right. Oh, sure, as always in Wisconsin, we had our extremely cold days, but all in all it was warmer, we had more days than normal get into temps that melted snow, and we had an early spring. And thanks, at least in part, to an ENSO index that stayed above the 0.5 mark from the 2009 May/June reading to the 2010 April/May reading we have continued to see warm temps.

So, imagine my surprise when I just randomly clicked on the index to see a May/June reading of -0.412.

Now, without any other context, this isn’t an extraordinarily low number. But there is a bit of context here that makes this a fairly fascinating number.

First, the index tracks on a two-month average basis. Thus, going from an April/May value of 0.539 to a May/June value of -0.412 (a drop of 0.951) must imply a very dramatic cooling in June. It’s one thing to see that kind of number when the previous one was -0.2, it’s quite another to see it after an El Nino-esque reading in the prior period.

So, I was curious to see how this compared to previous drops in the index.

I was both surprised, and not surprised, to see that this drop is the largest single month-to-month negative change in the index since the beginning of the readings in 1950.


I am not entirely sure what this means, and I suppose we need to see what happens over the next couple months. But I don’t like the timing. The impact of La Nina will have a few month lag, which puts us squarely in line for a harsh winter.

If you’re curious about the other laregest drops and what happened after those drops:

2nd place: -0.915 May/June 1998. This was a drop from an extremely high index reading to a still high reading. (From 1.982 tp 1.067) Within 3 months we saw La Nina, and it persisted 19 months, if you include one reading just above -0.5.
3rd place: -0.825 Apr/May 1954. This was a shift from a shallow La Nina value (-0.598) to a deep La Nina reading (-1.423). Including the initial value, this started a La Nina that persisted for 34 months.
4th place: -0.799 Oct/Nov 1950. This was a move from a negative reading (-0.381) to La Nina (-1.180). Something seems odd here. Deep La Nina readings are in place from the first month of 1950, then we had a jump, and then this drop. La Nina persisted another 5 months.
5th place: -0.775 May/June 1988. This was a move from barely positive (0.090) to La Nina negative (-0.685). This started a La Nina that persisted for 12 months.

Not to be a pessimist, but if you’re in my area, enjoy the next 2-3 months while you can.

10 Responses to “Uh Oh… Does the plummetting ENSO Index portend a cold winter?”

  1. Bob H said

    Good evening Joe. I dread the idea that the best case scenario is the ENSO dropping another .5 to .7 of a degree. This could make for an ugly winter.

  2. Paul Brand said

    This last winter was very strange with a record low AO. Very hot polar latitudes, and very cold mid-latitudes. Our area benefited on the warm side, being north of 49th. I don’t suppose we will see that again, but you never know.

    My toy model suggests that the effects of Nino peaked around March, with a +0.135C increase in global mean. Using NOAA’s projections of the Nino 3.4 index, Nina may have an impact of about -0.104C around March 2011. That’s about a -0.24C drop from Nino max to Nina min. (The impact on UAH/RSS is greater because the troposphere is more sensitive to changes in temperatures in the tropics).

    Regarding lag, I expect the temperature effect to hit negative in October (relative to the long-term mean).

  3. Joe, please read this over at wuwt
    if/when you get time u might compare this to what you found already.
    I have the same gut feeling about this winter, only for us it means more cold less snow(michigan), but for Georgia, Florida, Carolina/s it can be devastating!
    I thought you found a 6 year lag, this new study shows 10years? but from peak? or bottom?
    we are 10/9 years out…… we are in for it. I hope I am wrong, I do, no really.
    What if feb/march was #24’s peak?
    Music is great, I went back and play here at our college band for a year and had a ball,
    played a alto clarinet for one concert! mostly play the tenor sax. plunk on the tenor guitar some. thanks for being here.


    • The Diatribe Guy said

      Tim, thanks for that link. It was an interesting read, and this is the part that I found both interesting and entirely logical:

      “In these series of temperature he detected no, or hardly any, correlation between length of the sunspot cycle and temperatures averaged over the cycles. On the other hand, he found a strong dependence between the length of the sunspot cycles and the mean temperatures in the following period.”

      Of course, you would expect the imapct to lag. It only makes sense.

      Not to prop up my own study, but I believe my analysis is a bit more robust. He is looking at an entire period mean decrease over 11 or so years.

      My study gets to a similar spot, but it’s a bit different. My correlation analysis actually looks at average 12-month sunspot number as it relates to a change in temperature. Over time, the temperature corresponds at an 18-month to 2-year lag. What I have suggested is that temps tend to increase fairly rapidly a couple years after high sunspot activity, and then trail off at about a fourth of the pace with low activity. In the overall average cycle, this ends up generally balancing out to stable mean temps over the course of the cycle. If cycles are shorter with high sunspot activity, then the next cycle starts at a warmer base period and if there are a series of shorter cycles, it will correspond to increased temperatures. Likewise, longer, shallower, cycles will lead to cool temps, but at a much slower pace. Under a long period of shallow activity, it corresponds to about 0.1 degrees Celsius in cooling per year. In the short term, this isn’t particularly discernible as you throw in affects of El Nino and other things, but over 10-20 years, it has a very noticeable impact.

      I personally think my study is an important one, though I won’t say it’s perfect. A better study would include multivariate analysis to consider the impacts of ENSO, AMO, PDO, CO2, etc. In addition, Paul Brand has questioned whether or not the incremental affects are linear (ie, say I’m right that temps drop 0.1 degrees per year. Will that continue indefintely, or will there be some point where the cooling rate slows, and even reaches a limiting point? PB is probably correct in the assertion that the incremental affect is overstated, though that would complicate the analysis considerably, and with the amount of data, a more rigorous analysis may not even be possible without introducing credibility issues that outweigh the benefits. My opinion is that the o.1 degrees per year is probably reasonable for up to a decade – maybe longer, maybe a bit shorter – but that there will at some point be a slowing of that cooling and there will be some limiting value.)

  4. Bob H. said

    I think it is a bit premature to call last February/March the #24 peak. On the other hand, based on other’s predictions, it could be near the peak, in amplitude anyway. One curious point though is the solar flux index at about 80 (low was about 68) and the ap index is still quite low. I don’t believe we are going to see a sudden acceleration of sunspots in the near future based on what the data is doing.

  5. The Diatribe Guy said

    Speaking of sunspots, the last few times I’ve tried my NOAA sunspot link to the right, it’s been broken. I’ve been meaning to ask about where I can find the data now. I’d welcome any assistance.

  6. Bob H. said

    Good Afternoon Joe. I heard your plea for a new sunspot link and here it is:

  7. The Diatribe Guy said

    Bob, thank you very much! I have updated the link on the side of the page.

    Much appreciated.

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