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Saturday, December 5, 2015

El Niño in the Lower Troposphere - watch this space

Sou | 9:05 AM Go to the first of 17 comments. Add a comment
Some people wonder when El Niño will show up in the lower troposphere. It takes some months before the temperature of the lower troposphere peaks - up to three months later than the peak in surface temperatures. That means that it will still be a couple of months before the El Niño shows up strongly in lower troposphere temperatures.

Roy Spencer has posted an update of UAH lower troposphere temperature. Here is an update of the chart from a few weeks ago, with November 2015 included. This version is 6.04 beta which is slightly different to previous beta versions in the detail. The shaded area covers the general period of an El Niño - from around April in year 1 to March in year 2. The lower troposphere temperature doesn't normally peak till the end of the El Niño:

Fig 1 | Lower troposphere temperature anomaly - global. Data source: UAH


I've also plotted the chart just for the tropics. It is important to remember that air moves about a lot more than the oceans, so the air above the tropics in the lower troposphere isn't the only place that El Niño will affect.

Fig 2 | Lower troposphere temperature anomaly - tropics. Data source: UAH

I was planning to write a more extensive article on ENSO and the troposphere, but that will have to wait for another time. If you are interested in the subject, one article worth reading is by Geert Jan van Oldenborgh, KNMI at Ed Hawkin's ClimateLabBook. The article, "Is there a pause in the temperature of the lower troposphere?" is mainly about the slowdown in surface warming that occurred this century, but it touches on ENSO as well, pointing out that "the effects of El Niño are stronger in the TLT than in the near-surface temperature". What this means is that we can expect that Christopher Monckton and all the deniers at WUWT will have to press the restart button soon, when they want to claim that global warming has stopped. As Geert Jan van Oldenborgh concluded last December:
I conclude that beyond the effects of El Niño there is no pause in the warming in TLT either. As there is no evidence for a long-term trend in the Niño3.4 index, this means it will revert to normal before long and by that time the trend will pick up in the full TLT series as well. I think that may well be next year (2015), due to the (very small) El Niño this winter, but that may be overwhelmed by other natural variability. The TLT series looks so similar to the near-surface temperature series only because of a cancellation between the differences in the tropics and the high latitudes. However, neither shows that global warming stopped.


To complete the picture, below is a chart of surface temperatures in El Niño years, with this year's temperature anomaly up to and including October 2015:

Fig 3 | Global mean surface temperature anomaly in El Niño years. Data source: GISS NASA


References and further reading


There was a paper published a couple of years ago - it's quite technical so I'll be addressing some of the points it makes in a future article (maybe, I shouldn't make promises).

Scherllin‐Pirscher, B., C. Deser, S‐P. Ho, C. Chou, W. Randel, and Y‐H. Kuo. "The vertical and spatial structure of ENSO in the upper troposphere and lower stratosphere from GPS radio occultation measurements." Geophysical Research Letters 39, no. 20 (2012). DOI: 10.1029/2012GL053071 (open access)

Is there a pause in the temperature of the lower troposphere? - article by Geert Jan van Oldenborgh, KNMI at Ed Hawkin's ClimateLabBook


From the HotWhopper archives

17 comments:

MikeH said...

This reference is worth including for context

http://rabett.blogspot.com.au/2015/12/uah-tlt-series-not-trustworthy.html

It lends support to this comment from Carl Mears of RSS

"A similar, but stronger case can be made using surface temperature datasets, which I consider to be more reliable than satellite datasets"

http://www.remss.com/blog/recent-slowing-rise-global-temperatures

Sou said...

Thanks, Mike - that's an interesting article/letter. Hopefully one day soon there will be an updated independent analysis of the satellite data.

I don't think that UAH has made the code public yet, though the beta version has been through a few revisions. I don't know why deniers are under the illusion that it's perfect, when there have been so many changes. Which version is the perfect one?

And deniers are flat out wrong if they think that satellite temperatures are reported as "raw data". The satellites instruments don't even record temperature - the scientists have to estimate it by analysis and calculations and lots of adjustments (for drift etc).

Sou said...

Thanks, Mike - that's an interesting article/letter. Hopefully one day soon there will be an updated independent analysis of the satellite data.

I don't think that UAH has made the code public yet, though the beta version has been through a few revisions. I don't know why deniers are under the illusion that it's perfect, when there have been so many changes. Which version is the perfect one?

And deniers are flat out wrong if they think that satellite temperatures are reported as "raw data". The satellites instruments don't even record temperature - the scientists have to estimate it by analysis and calculations and lots of adjustments (for drift etc).

@whut said...

Will the article you are going to write on ENSO be one of those Tisdale specials? Too many of these "just-so" narrative stories for my taste. :)

Likely the only way that progress will be made is to quantitatively analyze all the data available and find some real patterns in ENSO and other climate indices. http://contextearth.com/2015/12/03/daily-double/

chrisd said...

"Which version is the perfect one?"

That's easy, Sou: Whichever one shows the least warming.

Remember that UAH used to be the one the deniers touted as the "gold standard." But then RSS started showing less warming and they deserted UAH in droves; overnight RSS became the "gold standard."

Sou said...

I wasn't intending to do any research myself, @whut (unless you call researching research research :D). I was only thinking of writing about ENSO from the perspective of what happens in the troposphere that has an impact on lower troposphere temperature. I've previously written about it in the general sense (see ref's above).

Hopefully, if I do get around to it, it will be more accurate and readable than a Tisdale article :)

William Connolley said...

> takes some months before the temperature of the lower troposphere peaks - up to three months later than the peak in surface temperatures.

I find that surprising. The atmosphere has precious little heat capacity. Why would the lag be so large? What's you source?

Sou said...

From the paper listed above, William - if I've understood it properly. Also the charts of global temperature above, especially for 97-98.

JCH said...

Seems like you should see it in the SST almost immediately... continents later.

jgnfld said...

That is one reason to doubt the satellite record as some sort of pure measure that overrides actual thermometers. The satellite record is A measure, certainly. But there is little to say it is THE record as deniers assert.

Can't tell you how many times I've seen a denier lately label the satellite record as "most reliable" or "most accurate".

Sou said...

At first glance the lag might seem counterintuitive, I suppose. We're talking about global temperature though, not just the air over the equatorial Pacific. This is why I am thinking of writing an article about how ENSO affects global atmospheric temperature in regard to the timing of the peak temperature response (or the low, in a La Nina). Also the fact that the troposphere temperature anomaly is exaggerated compared to the surface temperature in an ENSO event.

There are a number of papers on the subject, for example:

Su, Hui, J. David Neelin, and Joyce E. Meyerson. "Mechanisms for lagged atmospheric response to ENSO SST forcing*." Journal of climate 18, no. 20 (2005): 4195-4215. doi: http://dx.doi.org/10.1175/JCLI3514.1 (open access)

I don't expect to get to write about it for a few days - and I'll be reading a number of other papers on the subject - not just one or two - to get different perspectives.

William Connolley said...

Despite my surprise, you're right, that's what the paper says; and so do some of the papers it references dating back quite a way; so its not new. Its the kind of thing you can do GCM experiments on: force a change in the ocean, see how long the atmos takes to respond. Then you have more than one realisation to examine.

MikeH said...

Nick Stokes has plotted the adjustments made to the UAH satellite record from v5.6 to v6

" it is clear that even 10 years of adjustments to GISS are small in comparison to the adjustment to UAH this year"

http://moyhu.blogspot.com.au/2015/12/big-uah-adjustments.html

metzomagic said...

MikeH. Yep. UAH5.6 was already tracking about .02 below GISS recently, and now UAH6 is another .03 below that. Doesn't sound like much to yer average layperson, but on decadal scales it's a lot :-\

metzomagic said...

Sorry, the discrepancy is even bigger than that. It's at least 0.1C between GISS and the UAH6 of late. So much for eyeballing.

cosmicomics said...

More Carl Mears on satellite vis à vis surface data:

"My particular dataset (RSS tropospheric temperatures from MSU/AMSU satellites) show less warming than would be expected when compared to the surface temperatures. All datasets contain errors. In this case, I would trust the surface data a little more because the difference between the long term trends in the various surface datasets (NOAA, NASA GISS, HADCRUT, Berkeley etc) are closer to each other than the long term trends from the different satellite datasets. This suggests that the satellite datasets contain more “structural uncertainty” than the surface dataset."
https://www.washingtonpost.com/news/energy-environment/wp/2015/03/24/ted-cruz-says-satellite-data-show-the-globe-isnt-warming-this-satellite-scientist-feels-otherwise/

Tom Dayton said...

Even Roy Spencer now admits that satellite "measurements" of tropospheric temperature cannot and must not be used as proxies for surface temperature measurements, due to major unresolved issues in the assumptions used in the complex conversions of the microwave measurements into estimates of temperatures. (Spencer is one of the two main people responsible for the "UAH" satellite-based troposphere temperature estimations.) http://www.drroyspencer.com/2015/12/2015-will-be-the-3rd-warmest-year-in-the-satellite-record/#comment-203356.