Volcanoes and ENSO

One known issue with climate models is that they tend to suggest a larger response to a volcanic eruption than is observed. A recent paper by Lehner et al. shows that all large eruptions since 1951 coincided with El Niño events. El Niño events are a form of unforced variability that causes a period of warming. Hence, if a volcano occurs at the same time as an El Niño event, the influence of the volcano will appear smaller than if it occured when it was ENSO neutral or at the same time as an Le Niña event.

Consequently, what Lehner et al. (2016) consider is how climate models and observations compare if you correct the observations for ENSO events, or if you consider only models with co-incident El Niño events. This is shown in the figure below. The solid black line is the observed temperature, while the dashed black line is the observations corrected for ENSO events. The blue line is all the climate models considered, while the red line is only those that have co-incident El Niños. It’s clear that correcting the observations for ENSO events produces a better match (dashed black line and blue), as does considering only those climate models with co-incident El Niño events (solid black line and red line).

Credit : Lehner et al. 2016

Credit : Lehner et al. 2016

Of course, this is only one paper and – as it acknowledges – it doesn’t rule out that there may still indeed be model errors in the response to volcanic eruptions (forcings, aerosols, atmospheric circulation). It does, however, make a very good point in the conclusions

If a phenomenon under study is rare and the observational record short ….., potential superposition of forced and unforced variability needs to be taken carefully into account. These results are also important for paloclimate research, as potential superposition of eruptions and El Niño events during the last millennium adds another source of uncertainty to paleoclimate model-data comparisons.

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16 Responses to Volcanoes and ENSO

  1. Roger Jones says:

    Clever stuff. Impressive. We need more of this type work.

  2. It is impressive. Almost surprised noone had checked this before.

  3. BBD says:

    Almost surprised noone had checked this before.

    Me too. It’s like the long-form version of Schmidt et al. (2015) Basically the same conclusion, too: the models aren’t by any means as crap as ‘sceptics’ would have us believe.

  4. christian says:

    ATTP,

    I often Adjust Temperature-Data from effect of ENSO, so therefore i often had seen, that the Adjust-Response is more like in the CIMP5-Models, is that really new?? On the other Hand, its speculated, that intense tropical erruptions can force a El-Nino (because its weaken Hadley-Cell, which weakens Trade-Wind, which reduce Upwelling), so why Models dont tent to El-Nino on past erruptions…

  5. Christian,
    I don’t know if it’s new, or not, but I hadn’t come across this before.

  6. christian says:

    ATTP,

    Okay, i come across years ago, that is what i wonder about, its an interesting stuff, but the be on topic, if a vulcan erruptions is counter by an El-Nino, its should be clear, that CIMP5-mean would stronger respond, because the mean cancel nearly all internal variability in the Models itself out, but show then, that the most Models are not translate the vulcanic force in their physics to an El-Nino, this could be a part of wrong model physics, an error in input-forcing but also simple the effect of not synchronized internal variability in the models itself.

  7. christian says:

    Add:

    So the Question should not be, why Models show a stronger cooling, its clear, because of ENSO in the past events, the question should be, why the models not response in their internal variabilitiy like the Observation.

  8. the question should be, why the models not response in their internal variabilitiy like the Observation.

    Interesting, but do we know that the El Niño events are being initiated by the volcanic activity, rather than it simply being a coincidence?

  9. christian says:

    ATTP,

    In a physical way, its not just a coincidence, because there is a response to the trade winds, is this
    enough to force a El-Nino? Yes and No, because its should a question in which state the tropical pacific is in this moment of erruption, the ENSO is very complex and there are feedback processes if a El-Nino/La-Nina is in forming, if a erruption is on a forming La-Nina the response should not be the same as in neutral or forming El-Nino, in a state of a forming La-Nina (here i speculate) the already feedbacks in which cause stronger trade winds, so the erruption would only waken the La-Nina-Event, contrary on a state of El-Nino forming, in neutral it could be enough to force feedbacks which then cause a El-Nino. Also a point, the temperature has a delay due erruptions and the same we find in El-Nino, often then formed in the Year after erruption, still the time where the erruption has its most cooling effect.

    So in that way, if model physics correct, it could then be a problem of Synchronisation, real climate is in a neutral state, models in a La-Nina/El-Nino state, then the models would not respond like the real climate, although model physics is correct.

    There is some evidence in Paleorecords
    http://www.nature.com/nature/journal/v426/n6964/abs/nature02101.html
    http://onlinelibrary.wiley.com/doi/10.1002/jqs.1297/abstract

    Model:
    http://onlinelibrary.wiley.com/doi/10.1029/2006PA001304/full

  10. christian says:

    Or this nice peace: http://journals.ametsoc.org/doi/abs/10.1175/2007JCLI1884.1

    “Explosive volcanism cannot be said to trigger El Niño events per se, but it is found to raise their likelihood by 50% on average, also favoring higher amplitudes”

  11. izen says:

    Coincidence? correlation… causation!
    The idea that a explosive volcanic albedo altering eruption may trigger or enhance an El Nino is interesting…
    But if El Nino precedes the volcano then how could there be causation the OTHER way?
    Gaia responds to heat with vulcanism!?
    -grin-

  12. christian says:

    izen,

    “But if El Nino precedes the volcano then how could there be causation the OTHER way?”

    Hmm? I dont say that, i say, if there is neutral conditions or a el nino in developing, the erription could intens these event or can trigger the feedbacks to cause this event.

    “Gaia responds to heat with vulcanism!?”

    More contrary(first erruption then El-Nino), the Climate is protecting itself to response to a very strong apprupt change in forcing, we have first to know what El-Nino is, therefor we have to understand that the Nino-Basin is a Heat-sink in normal state, if there is a El-Nino, the Upwelling and heat sink is reduced below the thermocline, so the vertical transport is less and the warm will be captured in thermocline, so this means, that you need less incoming radiation to hold temperature in compare to normal states, because like said before, there is less losing Energy under the thermocline. Since the thermocline is well mixed, the temperature would be more stable or cool less if there is a strong negative forcing. As described in the link to the Papers, on a low frequenzy (or say on long times-scales) this is like a thermostat mechanismen, in times where there is a positive imbalance, its comes to a La-Nina-like Pattern, stronger Winds, stronger Upwelling cause better Mixing which slow down increase of temperature.

  13. smamarver says:

    Let’s not forget that El Nino does not warm the world. All oceans and seas contribute permanently heat to the atmosphere. El Nino is negligible in this respect. Here’s an interesting point of view on this subject: http://oceansgovernclimate.com/el-nino-does-not-warm-the-world/. On that site you’ll also find some other interesting articles on El Nino and climate change.

  14. Christian says:

    smamarver,

    Not interesting, more to simple and wrong

    1) the upper 100m in tropical pacific is the thermocline
    2) thermocline interacts with atmosphere, deeper Layer are isolated from atmosphere.

  15. On that site you’ll also find some other interesting articles on El Nino and climate change.

    That depend on what you find interesting.

  16. arhlupia says:

    Yeah, I agree with Christian. Even more, there is the posibility that solar forcing played a role in the Medieval Warm Period and the Little Ice Age. The decrease of solar radition (a small one due to Milankovitch actually) specificaly over equatorial Pacific could have trigered during LIA a permanent El Nino – like state as we said ; and the other way round during MWP. So this explains also the drought in the southern part of what is now USA, a preference for AO+, etc…

    “On the other hand, such a pattern is reproduced in simulations (19) using the low-order Cane-Zebiak (24) model of the tropical Pacific coupled ocean-atmosphere system. The discrepancy in the model responses may arise because the tropical Pacific “thermostat” mechanism (25) is not active in either the NCAR or GISS simulations. In (19), this mechanism is responsible for the La Niña–like response to the positive tropical radiative forcing of the MCA that arises from a combination of relatively high solar irradiance and inactive tropical volcanism. Although there is still a vigorous debate regarding the nature of the response of the tropical Pacific to anthropogenic radiative forcing [e.g., (26)], paleoclimate evidence examined here, as elsewhere [e.g., (19,27)], appears to support a thermostat-like response, at least for natural radiatively forced climate changes in past centuries.”

    http://www.meteo.psu.edu/holocene/public_html/shared/articles/MannetalScience09.pdf

    I don’t have recently followed up the development of this particular field of research, so I don’t know if there is more recent and more pertinent paper. But it seems it’s still on the table. The real difficulty I think, as suggested by Christian, is the failure of the models to simulate the ENSO. We still don’t really understand how this oscillation work and how it is triggered. The fact is that models are able to simulate the forced answer of the climate of course, but still not its variability. So the problem is perhaps more in why models don’t triggered an El Nino after a volcanic eruption, than in the excessive answer to volcanic forcings.

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