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El Niño and the record years 1998 and 2016

Filed under: — stefan @ 4 November 2017

2017 is set to be one of warmest years on record. Gavin has been making regular forecasts of where 2017 will end up, and it is now set to be #2 or #3 in the list of hottest years:

In either case it will be the warmest year on record that was not boosted by El Niño. I’ve been asked several times whether that is surprising. After all, the El Niño event, which pushed up the 2016 temperature, is well behind us. El Niño conditions prevailed in the tropical Pacific from October 2014 throughout 2015 and in the first half of 2016, giving way to a cold La Niña event in the latter half of 2016. (Note that global temperature lags El Niño variations by several months so this La Niña should have cooled 2017.)

The hot El Niño year of 1998 is comparable to 2016, since both years followed the two hitherto strongest El Niño events. And 1998 was followed by a cool 1999, only ranked #7 in the list of hottest years until then. So here is a comparison of 1998 versus 2016. Let us first look at the full time series of GISTEMP global temperature data, see Fig. 1.

Fig. 1 GISTEMP global temperature data, in 12-months running average (anomalies relative to the first 30 years). The data are available monthly and averaging over 12 months removes a considerable amount of month-to-month ‘noise’. Showing only calendar-year averages would lose some information – e.g. it would only fully show peaks in temperature if by chance the maxima aligned with the calendar year.

The El Niño peaks in 1998 and 2016 are clearly seen. It has been shown in several studies (e.g. Foster and Rahmstorf 2011) that El Niño is one of the main causes – perhaps the main cause – of short-term variability in global temperature. The following graph overlays those 2 El Niño peaks by shifting the 2016 peak back in time by 18 years and down by 0.4 °C.

Fig. 2 The two El Niño peaks in global temperature from Fig. 1, zoomed in and overlayed by shifting the 2016 peak back in time by 14 years and down by 0.4 °C. The darker red curve is the 2016 peak, as in Fig. 1.

The two peaks align very well. The first conclusion is that global temperature evolution over the last few years is very similar to that around 1998 – except the Earth is now 0.4 °C hotter. That’s 0.4 °C warming over 18 years, corresponding to 0.22 °C per decade – a bit more than expected from the long-term global warming trend since 1980, which is 0.17 °C per decade in the GISTEMP data. (So much for the “no warming since 1998” meme so popular with climate deniers.)

The second observation is that initially temperatures climbed down from the peak as fast as in 1998 – but then the cooling slowed down, and the last 12 months haven’t just been 0.4 °C warmer than in 98/99 but closer to 0.5 °C warmer. So it is clear that our planet is not cooling off as fast as after the 1998 El Niño peak. I wouldn’t over-interpret this – we’re looking at a really short interval here, so it is clearly no reason to diagnose a noteworthy acceleration of global warming. But there certainly is no sign of global warming slowing down. It will be interesting to watch how this continues over the next months; the ENSO forecast is for developing La Niña conditions again this coming fall/winter.

14 Responses to “El Niño and the record years 1998 and 2016”

  1. 1
    Christian John says:

    Stefan,

    “we’re looking at a really short interval here, so it is clearly no reason to diagnose a noteworthy acceleration of global warming.”

    I would tend to say, that there is a jump, on a physical way, the climate system is interacting with antropogenic Forcing, i think sometimes in a non linear way, this view can be supported if you looking at the ocean temperature in the first 100 meters: https://data.nodc.noaa.gov/woa/DATA_ANALYSIS/3M_HEAT_CONTENT/DATA/basin/yearly_mt/T-dC-w0-100m.dat

    for latest data:
    https://data.nodc.noaa.gov/woa/DATA_ANALYSIS/3M_HEAT_CONTENT/DATA/basin/3month_mt/T-dC-w0-100m4-6.dat

    You see clearly the difference between 1998/1999 to 2016/2017. On the other Hand, this layer is the most important one, because of atmosphere-ocean-interactions due the mixing layer. If you would correct 2017 by MEI-Index you would get the the warmest year and strongest year to year increase.

    So where it come from? My opinion:

    Because since 1998 energy was stored in lower ocean layers (below 100m) because of more upwelling, same time, the first 100m gets relativ cool compared to forcing, since 2015, upwelling has brocken down and first 100m aprupt adjust to forcing, so why its warmer now then after 1998, is possibly because before the event, the relativ imbalance in the first 100m was stronger then in 1997

    Greets

  2. 2
    Matthew R Marler says:

    “we’re looking at a really short interval here, so it is clearly no reason to diagnose a noteworthy acceleration of global warming.”

    I agree, fwiw. The 1998/1999 peak, rebound, and recovery to a higher level was about 5 years in duration. This could be like that.

  3. 3
    PaulS says:

    I think a large part of what’s going on has to do with Arctic amplification. The normal seasonal cycle of Arctic amplification is coincidentally basically the same as for the global average response to El Nino, even though the Arctic warming is probably at least partly independent of El Nino. And as we get further from the baseline that seasonal cycle becomes more exaggerated.

    That means the 2016 El Nino response maybe looks stronger than it really was. If you make the same comparison as above but look at GISS cropped to 90S-60N, the 2016 event peaks significantly lower than 1998, and is closer to the less strong 1988 event. A number of other indicators also suggest that 2016 wasn’t as severe as 1998 or 1983, belonging to a lower class of merely very strong events.

    Likewise, the 12-month running mean probably hasn’t gone down as much in 2017 because very strong Arctic warmth persisted during the first few months of this year.

  4. 4

    The other large contribution to year-on-year variability of the global mean temperature is the winter weather in Siberia and Canada. This is a large area with very large variability due to random weather on short time scales, which even averaged out over a year gives s sizeable contribution. And yes, it was very warm there the 12 months.

  5. 5
    David Beach says:

    The question that arises is whether El Ninos are increasing in frequency with increasing ocean temperatures. Is there any significant statistical relationship?

  6. 6
    Carbomontanus says:

    0,4/1.8= 0,222222222 /decade.

    ‘I am surprized.

    S.K.

  7. 7
    Carbomontanus says:

    But, Hr Stefan
    I lack a proper discussion also of the minimals along the curve. This hunting for Guinness records may often overshadow the negative side of the curve.

    There has been a gtremendous rain in Southern Norway last month, car doors and Windows 3 times under water, beat that! When will People learn? And we are pumping water in the cellar again. Hamburg had it even worse. “Hochwasser” they Call it.
    S.K.

  8. 8
    Random says:

    Alas – nothing learned from dealing with deniers. Above Fig. 2 will be ‘cited’ up and down by deniers that 1998 truly had been warmer than 2016 – see, even realclimate says so!!11!1 You could have included the 0,4 degree thingy a gazillion times more to no avail. Unforced error, I would say…

    [Response: It is why I put it in the figure and not just the caption. -stefan]

  9. 9
    Random says:

    Oops – I could have sworn that part wasn’t there when I made the comment…

  10. 10
    Bob Loblaw says:

    It is why I put it in the figure…

    Stefan, meet PhotoShop. PhotoShop, meet Stefan.

    There are people out there who will gladly mask out that detail and still claim it came from RealClimate!

  11. 11
    Paul D. says:

    #8 and #10

    Agree; I understand the need for the 18-year leftward shift – but shape of the curves could still be compared without the 0.4 degree downward shift in the 2016 curve.

  12. 12
    mrlee says:

    Bob Loblaw: Wonderful! Deniers photoshopping the figure would discredit them as dishonest (as if they needed further discrediting) in the eyes of people still not totally brainwashed.

  13. 13

    This is really interesting. How can I get a synopsis of this article for consumption by our students at the Institute for Climate Change and Adaptation in the University of Nairobi? I’d also like to see the projected impacts for East Africa

  14. 14
    rasmus says:

    The article is open access – see the reference above.

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