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Thursday, September 10, 2009

The Relationship Between ENSO And Global Surface Temperature Is Not Linear

I’ve moved to WordPress.  This post can now be found at The Relationship Between ENSO And Global Surface Temperature Is Not Linear

The first part of this post is a rehashing of points made in earlier posts here and at WattsUpWithThat, including “Multiple Wrongs Don’t Make A Right, Especially When It Comes To Determining The Impacts Of ENSO”, and “Regression Analyses Do Not Capture The Multiyear Aftereffects Of Significant El Nino Events.” I will keep repeating the message with each new paper that attempts to perpetuate the misconceptions, or misunderstandings, or misinterpretations of ENSO until the message gets through.

The point introduced in this post: The message has landed in at least one paper, but more on that in the Closing.

Expect to find a repeat of this message as soon as the Journal of Climate publishes the 2009 Thompson et al paper “Identifying signatures of natural climate variability in time series of global-mean surface temperature: Methodology and Insights.” It also fails to account for the long-term cumulative effects of ENSO on Global Surface Temperature.


Lean and Rind in their 2009 paper “How Will Earth’s Surface Temperature Change in Future Decades?” make a common error. Link to Lean and Rind (2009):

And there are many other papers that err in the same way. These include:

Foster et al (In Press) “Comment on ‘Influence of the Southern Oscillation on tropospheric temperature’” JOURNAL OF GEOPHYSICAL RESEARCH, VOL. ???, XXXX, DOI:10.1029/

Lean and Rind (2008) “How Natural and Anthropogenic Influences Alter Global and Regional Surface Temperatures: 1889 to 2006” [GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L18701, doi:10.1029/2008GL034864, 2008].

Santer, B.D., Wigley, T.M.L., Doutriaux, C., Boyle, J.S., Hansen, J.E., Jones, P.D., Meehl, G.A., Roeckner, E., Sengupta, S., and Taylor K.E. (2001), “Accounting for the effects of volcanoes and ENSO in comparisons of modeled and observed temperature trends,” J. Geophys. Res., 106, 28033–28059.

Thompson, D. W. J., J. J. Kennedy, J. M. Wallace, and P. D. Jones (2008), “A large discontinuity in the mid-twentieth century in observed global-mean surface temperature,” Nature, 453, 646–650, doi:10.1038/nature06982.

Trenberth, K.E., J.M.Caron, D.P.Stepaniak, and S.Worley, (2002), “Evolution of El Nino-Southern Oscillation and global atmospheric surface temperatures,” J. Geophys. Res., 107 (D8), 4065, doi:10.1029/2000JD000298

Wigley, T. M. L. (2000), “ENSO, volcanoes, and record-breaking temperatures,” Geophysical Res. Lett., 27, 4101–4104.ENSO, volcanoes and record‐breaking temperatures

All of these papers assume that the relationship between ENSO and Global Surface Temperature is linear. Lean and Rind (2009) present this assumption in their Figure 1, which is Figure 1 of this post.

Figure 1

Note how the ENSO signal in Cell B of Figure 1 is fundamentally a scaled-down version of the Multivariate ENSO Index or MEI. Lean and Rind note the use of the MEI, “The multivariate ENSO index, E, is a weighted average of the main ENSO features contained in sea-level pressure, surface wind, surface sea and air temperature, and cloudiness [Wolter and Timlin, 1988].” The other papers noted above use others ENSO indices such as Southern Oscillation Index data, NINO3.4 or NINO3 SST anomalies, or Cold Tongue Index SST anomalies as their ENSO reference, and they all make the same erroneous assumption.

The assumption made is that the relationship between ENSO and Global Surface Temperature is linear. It is not. There are residual effects of significant El Nino events, like those in 1986/87/88 and 1997/98. These residual effects create upward step changes in Global Surface Temperatures, Figure 2, that are seen as divergences between the ENSO signal and Global Surface Temperatures. These divergences are mistaken for the impacts of Anthropogenic influences.

Figure 2

As noted in Figure 2, these step changes are easily seen in two datasets. The first is the SST anomalies of the Eastern Indian and Western Pacific Oceans, Figure 3.
Figure 3

The area represented by the East Indian and West Pacific Ocean SST anomalies (the black curve in Figure 3) is shown in Figure 4. The coordinates are 60S to 65N, 80E to 180. It occupies a significant portion of the world oceans, in the range of 25 to 30% of global sea surface from 60S to 65N.
Figure 4

Refer to the following posts for further information:
Can El Nino Events Explain All of the Global Warming Since 1976? – Part 1
Can El Nino Events Explain All of the Global Warming Since 1976? – Part 2

The second dataset these step changes in response to the 1986/87/88 and the 1997/98 El Nino events can be seen in are the TLT anomalies of the Mid-to-High latitudes of the Northern Hemisphere, Figure 5. The 1986/87/88 and 1997/98 El Nino events are highlighted in the Hovmoller.
Figure 5

Refer to my post:
RSS MSU TLT Time-Latitude Plots...Show Climate Responses That Cannot Be Easily Illustrated With Time-Series Graphs Alone”.


The myths of Anthropogenic Global Warming are maintained by the continued misrepresentation of the impacts of ENSO on Global Surface Temperatures. But as noted in the Introduction, at least one paper, Stockwell and Cox (Submitted) “Comment on ‘Influence of the Southern Oscillation on tropospheric temperature’ by J. D. McLean, C. R. de Freitas, and R. M. Carter”, has proposed an alternate explanation.

Link to abstract:

Stockwell and Cox write in the abstract, “We demonstrate an alternative correlation between the El Nino Southern Oscillation (ENSO) and global temperature variation to that shown by McLean et al. [2009]. We show 50% of the variation in RATPAC-A tropospheric temperature (and 54% of Had-CRUT3) is explained by a novel cumulative Southern Oscillation Index (cSOI) term in a simple linear regression. We review evidence from physical and statistical research in support of the hypothesis that accumulation of the effects of ENSO can produce natural multi-decadal warming trends. Although it is not possible to reliably determine the relative contribution of anthropogenic forcing and SOI accumulation from multiple regression models due to collinearity, these analyses suggest that an accumulation ratio cSOI/SOI of 4:8 +/- 1:5% and up to 9 +/- 2% is sufficient for ENSO to play a large part in the global mean temperature trend since 1960.”

In time, maybe (maybe not), the true nature of ENSO will be accounted for by climate scientists in their analyses and GCMs. Until that time, I will continue to repeat what I’ve documented in numerous ways. The relationship between ENSO and global surface temperature is not linear.


H/T to David Whitehouse who noted in his post Forecasting the Earth’s Temperature that Lean and Rind (2009) had been published.


John said...

Bob -

Keep plugging away. Hopefully scientists will turn their attention to this phenomenon and bolster your argument, or at the least address it in their analysis so science can continue to improve.

One question - Stockwell and Cox talk about variation - are they saying that they view that ~50% of the observed warming trend is explained by ENSO? I.e. if we have a trend of .2c/century, .1c/century of that is purely ENSO? Or are they referring to a different number?

Also - are you aware of anyone who has tried to disprove your step-up theory? It seems so sensical and supported that I am suprised noone has tried to address it and disprove it as a means of bolstering their own positions.

Thanks as always, and keep up the good work.

Bob Tisdale said...

John: Stockwell and Cox answer your question in the full version of the paper.
My take is that they're saying that the cumulative SOI signal represents 50% of the rise in surface temperature since 1960. But keep in mind that the SOI is the surface pressure component of ENSO. There are differences between the surface pressure and SST indices. Had they used one of the ENSO SST Indices like NINO3.4 SST anomalies, it's likely they would have gotten better results.

And as far as I know, no one has challenged the step changes. It would be tough for me to fabricate them. They're in the data.

Layman Lurker said...

Bob, I enjoy following your work. I believe your take on the non linear impact of ENSO is correct and will be confirmed by the statistical analysis in the forthcomming SC09.

David Stockwell said...

Hi, John, the 50% refers to the amount of variance explained by cSOI alone. When you correlate with anthropogenic forcing, you get around 60% explained. When you put AF and cSOI together in the same equation, its about 60:40 in favor of AF. But given that both of AF and cSOI are increasing monotonically over the period, I don't really trust this breakdown, which is why I didn't report it.

Trying to recover relative contributions from linear regressions is farly problematic IMHO unless there is a lot of data from independent variables, and I really wanted to leave that question for another time when I can do it justice.

Plus it was SOI, which was the context of McLeans paper, as Bob mentioned.

Suffice to say the statsitical models shows that the contribution of ENSO could be 'large'.

John said...

Thanks for the answer, David. I appreciate it.

Has your comment been accepted by the journal yet? Have they had any feedback/pushback?

I notice (based on the info in the comment) that you are not a professor - has that proven to make the road tougher to get your comment accepted? I imagine there is significant bias.

Do you deviate from Bob in thinking that the vast majority of the temperature rise is attributable to ENSO? Are you more in the, to use your estimate, the 60/40 camp? Just curious.

Thanks in advance.

David Stockwell said...

John, It was hard to get published when I was a professor. I think its due to the content really. If you have a name then you can get a free ride occasionally, but that can be a bad thing too as it will come back and bite you if the work is poor.

I have some recent results that put it more 40/60 against AGW. I wouldn't call it AGW either. Its just a natural cyclostationary phenomena, vs some kind of trending over the last 100 years.

fred said...

The step changes may simple be an illusion. Ie an increasing linear trend with ENSO-like noise superimposed might by chance appear to contain 2 step changes.

Then again even if global temperature reacts to ENSO in a non-linear fashion I don't see what that has to do with AGW. If global temperature moves in fits and starts in a warming world I don't see how that has any bearing on the cause of such warming.

Bob Tisdale said...

Fred: You wrote, “The step changes may simple be an illusion. Ie an increasing linear trend with ENSO-like noise superimposed might by chance appear to contain 2 step changes.”

Apparently you did not refer to the linked posts. Here they are again:
The first includes a video that illustrates the process that causes the shifts in the East Indian and West Pacific SST anomalies. Can’t miss the effect. They may not be true steps, but they are rises from significant traditional El Nino events. The rises in the East Indian and West Pacific SST anomalies have excessive decay times, and before the East Indian and West Pacific SST anomalies can decay fully, the next but lesser El Nino (Modoki) event bumps the SST anomalies of that area back up again. And the same thing happens a few years after that and again a few years later, giving the impression of a step. Along comes the next significant traditional El Nino that relocates a significant amount of warm water from the Pacific Warm Pool and there’s another shift in East Indian and West Pacific SST anomalies with an excessive decay time and the subsequent bumps from lesser El Nino Modoki events. They appear to be two steps.

The effect can also be seen in the Hovmollers of the Low Latitude Pacific SST anomalies:

The same shifts with excessive decay times can also be seen in the Hovmollers of Global TLT anomalies. The TLT anomalies of the mid-to-high latitudes of the Northern Hemisphere shift upward after the same significant El Nino events, and the subsequent lesser El Nino Modoki events help to maintain the new levels. They’re tough to miss in the Hovmollers:

There’s nothing new there. The poleward heat transport associated with El Nino events is widely known.

Is it a lucky coincidence that the shifts in East Indian and West Pacific SST anomalies and the shifts in the TLT anomalies of the mid-to-high latitudes of the Northern Hemisphere occur during the significant traditional El Nino events of 1986/87/88 and 1997/98? Unlikely. It’s definitely not El Nino noise imposed over a linear rise. Not when there’s a process that’s visible.



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