Note: Bob wrote to me with this caveat:
Caution: Those Hovmollers will bring you back to the 60s if you stare at them too long.
Guest post by Bob Tisdale
Hovmoller graphs are used in some discussions of climate variability. Many times they’re used when illustrating surface and subsurface processes that take place during ENSO events. And for those who aren’t familiar with them, they can look like a flashback to the pop art of the 1960s.
When used for variables such as SST anomalies of two portions of the Low Latitudes of the Pacific, the Hovmollers can help to show the upward step changes that result from significant El Nino events.
EASTERN PACIFIC LOW LATITUDE SST ANOMALY HOVMOLLER
Figure 1 is a time-latitude plot of Eastern Pacific Low Latitude SST anomalies (30S to 30N, 178W-70W) from January 1982 to July 2009. The x-axis is time (same as a time-series graph), the y-axis is latitude, and SST anomalies are color coded. This Hovmoller plot is available through the NOAA Earth System Research Laboratory (ESRL) Physical Sciences Division (PSD) website linked later in this post.
http://i27.tinypic.com/2lb96e.png
Figure 1
The significant El Nino events of 1982/83, 1986/87/88 and 1997/98 stand out in red in the tropical latitudes, and the subsequent La Nina events show up in purples and blues. The lesser (secondary?) El Nino events that formed in groups after the 1986/87/88 and 1997/98 El Nino are also obvious. And for those who aren’t aware of the timing and magnitudes of ENSO events, I’ve grafted a time-series graph of NINO3.4 SST anomalies to the time-latitude plot in Figure 2.
http://i30.tinypic.com/29ws3g9.png
Figure 2
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Note 1: The NINO3.4 SST anomalies in 1993 are not classified as a full-fledged El Nino. They rose into El Nino ranges (above 0.5 deg C) but did not remain there long enough to classify it as an El Nino event.
Note 2: Refer to my post “Similarities of the Multiyear Periods Following Significant El Nino Events Since 1970” for a discussion on the El Nino events that appear to be secondary to the significant ones of 1972/73, 1986/87/88 and 1997/98.
Note 3: The notation “3RM” in the right-side of the Hovmoller title block stands for 3-month running mean.
Note 4: The coordinates used by the NOAA/ESRL/PSD for the East Pacific (178W-70W) includes all of the Gulf of Mexico, part of the Caribbean, and a small portion of the North Atlantic.
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Figure 3 is the Time-Series graph of the SST anomalies for the area of the Eastern Pacific (30S to 30N, 178W-70W) illustrated by the Hovmoller plot in Figure 1. The linear trend line shows that SST anomalies for the Low Latitudes of the Eastern Pacific have not risen over the past 29 years. If fact, there has been a very slight decline.
http://i31.tinypic.com/29ap5dc.png
Figure 3
WESTERN PACIFIC LOW LATITUDE SST ANOMALY HOVMOLLER
A Time-Series graph of the western counterpart of Pacific Low Latitude SST anomalies are shown in Figure 4. A typical description of that dataset might read, The Western Pacific Low Latitude SST anomalies (30S-30N, 120E-180E) show a great deal of annual variability. Over multiyear spans, they rose sharply from 1980 to 1999 and have declined slightly since then.
http://i30.tinypic.com/2v8guwp.png
Figure 4
A linear trend line, Figure 5, gives the dataset the appearance of a noisy constant rise in SST anomalies.
http://i25.tinypic.com/1zovs3k.png
Figure 5
But the Hovmoller of SST anomalies for the Western Pacific Low Latitudes, Figure 6, illustrates something entirely different. It clearly shows that, after the 1997/98 El Nino, SST anomalies in Western Pacific rose in one step. SST anomalies greater that 0.7 deg C (Illustrated in Red) appear very infrequently before 1998. But after 1998, SST anomalies greater that 0.7 deg C are common. The El Nino event of 1986/87/88 also caused an upward step change in Western Pacific Low Latitude SST anomalies, but it’s difficult to see since it was smaller in magnitude. The eruption of Mount Pinatubo in 1991 also lowered SST anomalies for a few years. This masks the step change in 1988 and emphasizes the rise in 1994 and 1995, which is a rebound from the drop caused by volcanic aerosols.
http://i30.tinypic.com/xpon7k.png
Figure 6
In Figure 7, a NINO3.4 SST anomalies time-series graph has been spliced to the time-latitude plot of the Western Pacific Low Latitude SST anomalies to show the timing of the ENSO events.
http://i26.tinypic.com/2dhtr0n.png
Figure 7
Figure 8 combines the time-latitude plot and time-series graph of SST anomalies for the Low Latitudes of the Western Pacific. To highlight the step changes, I’ve added average SST anomalies for the periods before and after the significant El Nino events of 1986/87/88 and 1997/98. From January 1982 to December 1987, the average SST anomalies were -0.04 deg C; from January 1988 to December 1997, they were 0.05 deg C; and from January 1998 to July 2009 the SST anomalies for the Low Latitudes of the Western Pacific were 0.34 deg C.
http://i31.tinypic.com/24o500y.png
Figure 8
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Note 5: The processes associated with significant ENSO events that caused the step changes illustrated in this post are the same as those shown in:
“Can El Nino Events Explain All of the Global Warming Since 1976? – Part 1”, and
“Can El Nino Events Explain All of the Global Warming Since 1976? – Part 2”
Note 6: Time-latitude plots of global TLT anomalies from RSS were used to illustrate the step changes in TLT anomalies caused by the significant El Nino events of 1986/87/88 and 1997/98. Refer to:
“RSS MSU TLT Time-Latitude Plots… …Show Climate Responses That Cannot Be Easily Illustrated With Time-Series Graphs Alone”
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Figure 9 illustrates the Hovmoller graphs as downloaded from the NOAA/ESRL/PSD webpage:
http://www.cdc.noaa.gov/map/clim/sst.shtml
Specifically, this link:
http://www.cdc.noaa.gov/map/images/sst/sst.pacific.hov.gif
I took the liberty of splitting them for this post.
http://i25.tinypic.com/x45306.png
Figure 9
CLOSING
The SST anomalies of the Low Latitudes of the Eastern Pacific mimic NINO3.4 SST anomalies, and they present a slightly negative trend. But there are upward step changes in the Western Pacific Low Latitude SST anomalies caused by the El Nino events of 1986/87/88 and 1997/98, confirmed by the Hovmoller plot, and the SST anomalies for this area have a substantial positive trend. Combine the two datasets and the result is a curve, Figure 10, that clearly shows the influence of ENSO, but has a positive trend. This is the same effect the East-Indian and West Pacific Oceans, which also exhibit the ENSO-induced step changes, have on global SST anomalies.
http://i31.tinypic.com/a9kz9y.png
Figure 10
In “Evolution of El Nino-Southern Oscillation and Global Atmospheric Surface Temperatures”, Trenberth et al (2000) state in their Conclusions, “Although it is possible to use regression to eliminate THE LINEAR PORTION of the global mean temperature signal associated with ENSO, the processes that contribute regionally to the global mean differ considerably, and THE LINEAR APPROACH LIKELY LEAVES AN ENSO RESIDUAL.” [Emphasis added.]
http://www.cgd.ucar.edu/cas/papers/2000JD000298.pdf
As illustrated in this post and in those linked, that residual accounts for most if not all of the global TLT and SST warming since the late 1970s. Climate scientists attempt to attribute the residual to anthropogenic causes, when it is clearly a result of significant El Nino events.
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Trippy…
Bob:
This is intriguing. What happens when you look at high latitudes using the same tools? In particular, what do you see happening around Western Antarctica?
Hmmm… Thanks to yer Hovmoller graphs, I now have Itchycoo Park running through my head every time I look at them;-)
http://www.youtube.com/watch?v=VJzcF0v1eOE
Bob, interesting and very colorful. No matter how i look at it, my eyes settle on the huge purple anomaly associated with the 1998-2001 La Nina. We have had this discussion before. The UAH LTL GLOBAL temp. anomaly did not exceed .300 for 33 straight months. We have not come close to that in terms of depth or breadth since then. In addition, the highs associated with the 1997-1998 El Nino have not been breached. IMHO, until the highs/lows of 10 years ago are exceeded, i think it is safe to say the earth has achieved thermal balance for a remarkable period. In my opinion, just looking at the ENSO weekly charts, sans regression analysis, give one the overall picture. Thank you for your very interesting analysis. fm
From an “eye-ball” perspective, it seems as if the southern latitudes (mostly ocean) warm up more consistently (anomalies) than those northern during El Ninos. It also seems that greater warmth is distributed to the farther north in the NH? Is this an accurate observation, and, if so, does it have any importance re “natural” global warming and cooling? For example, if El Nino heating of the well-mixed layer of the ocean is sent (travels) far northward, does it cool off (lose heat) faster in the NH, leaving us with an overall cooler world, as it seems we have today? (Sorry , it is difficult for me to find non-anthropogenic language to explain.)
Good work, Bob. I think you make a strong case for your contention that the recent warming is a “step” change following the 97-98 El Nino. I would conclude that this “warming” is not directly related to solar, at least not the lunisolar influence that Anthony and I have identified, because the latter is more uniform and less dramatic in its influence.
I would also conclude that all the work claiming that the solar influence cannot explain the last 20-30 years of warming doesn’t mean that it (solar) hasn’t continued to have its usual influence. It is just that the latter is relatively small in relation to what has happened in recent decades, and especially in the last decade.
So do you have a theory as to where all this heat, or energy, came from? It just comes “out of nowhere” with the “super” El Nino of 97-98, and then is distributed latitudinally in the years to follow. But where did it come from?
Can’t the author at least mention once what does mean ENSO and SST and any other jargon-ish acronym?
SST ? Super Sonic Transport ? A model of car from the seventies? huh?
Bernie: You asked, “What happens when you look at high latitudes using the same tools? In particular, what do you see happening around Western Antarctica?”
Those Hovmillers were prepared by NOAA/ESRL/PSD, not by me. I would love to be able to recreate them for other areas around the oceans. I wrote to the PSD asking if they had others of mid-to-high latitude SST anomalies. They replied with a no, but forwarded a link to their webpage that allows users to create their own Hovmollers. They admit the site has problems, and when it works I haven’t been able to get the same color scale.
http://www.cdc.noaa.gov/map/time_plot/
However, the SST anomalies for the Southern Ocean south of the Southeast Pacific (90S-60S, 100W-70W) does not hold any surprises.
http://i26.tinypic.com/30m1hqq.png
You have to keep in mind that Southern Ocean SST anomalies have been dropping since the late 1980s or 1990s (depending on the dataset). Here’s the ERSST.v3b version:
http://i41.tinypic.com/29zxus7.jpg
I’ve done a number of posts on the Southern Ocean (or that have included discussions of the Southern Ocean in the comments):
http://bobtisdale.blogspot.com/search?q=Southern+Ocean
Inna godda divida baby
Basil, I think by elimination, the heat source can be found. It can’t be longwave (not strong enough). So that leaves out greenhouse gasses, water vapor, and warming type clouds. It has to be shortwave radiation. I would be looking at tropical weather patterns prior to and during the 98 El Nino.
“Climate scientists attempt to attribute the residual to anthropogenic causes, when it is clearly a result of significant El Nino events.”
But what causes the post-El-Nino heating? The heat has to come from somewhere. Climate scientists would presumably argue that it is the result of gradual heating caused by radiative imbalance due at least in part to human GHGs. Given the complex cycles-within-cycles of the climate system, one would not necessarily expect the SST to smoothly track the increase in CO2.
GHG’s cannot be responsible for warm 98 SST’s. They only reflect longwave radiation back to the water surface and then cannot penetrate anything but the thin mm of “skin” of the surface. Any warming at this level gets evaporated quickly. My guess is a weather pattern variation set up around the equatorial tropics that allowed shortwave radiation (which heats like a bugger and deeply) to heat the water over an extended period of time and in seasonal waves. I would guess, the pattern included dry still air and no clouds over an extended period. The doldrums anyone?
Interesting pattern of tropical “bursts” of energy: …1988, 1998, 2008.
1982 broke the pattern – but then again, 1982 was part of the beginning of the rise from the 1970-1975 post WWII “low” temperatures.
—
I too have NEVER heard of a reason for the 1998 bubble of energy:
Where did it come from?
Where did it (that sudden rise) go?
Why was 1998’s global temperatures higher than before? –Sure, 1998 was during a “perfect” El Nino. of course it was. My question is: Where did the 1998 El Nino come from (what was the cuase of the El Nino?), and what was the source of energy for that El Nino?
pyromancer76: You asked a bunch of questions. I started to answer one about the transport of heat from the tropics to mid latitudes and got carried away and it morphed into an observation of the “Sympathetic El Nino” in the western Indian Ocean, which was also a response to the 1997/98 El Nino. Then it got back on track, so bear with me.
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The 1997/98 El Nino released a significant amount of heat that was transfered by ocean currents away from the tropics. You can see that in the SSH anomaly video from JPL.
About 45 seconds into the video, around June or July 1996, the Pacific anomalies are primarily in the cooler colors. In September, the SSH around the PWP starts to rise. By early December 1996, it’s quite elevated. Then around Christmas of that year, the first Kelvin wave shoots to the east across the equator. And with the second Kelvin wave the El Nino gets going in full.
Now here’s the fun part of that El Nino. Let the video run forward until November or December of 1997. The El Nino is peaking in the eastern Pacific. But look at the western Indian Ocean. There’s a significant rise in SSH there, and a significant rise in SST. WHY?
It appears that the drop in the SST anomalies in the Pacific Warm Pool (aka Indo-Pacific Warm Pool) increased the delta T between the east and west Indian Ocean which in turn increased the trade winds in the tropical Indian Ocean. This pushed more warm surface water to the western Indian Ocean than usual.
Now let the video play until May 1998 and watch the warm water in the Western Indian Ocean slam back east, another way the PWP gets recharged.
By April 1999 there is a significant amount of warm water running around the mid-to-high latitudes of both hemispheres of the Pacific that wasn’t there before the El Nino. So the OHC of the mid-to-high latitudes of the Pacific rose as a result of the 1997/98 El Nino. Let the video run to June 2000. We’re still in the La Nina recharge phase and there’s still a lot of extratropical heat running around the Pacific. But by this time, the warm water volume (a proxy for OHC?) of the equatorial Pacific is back to the level it was at in 1996, a year before the 1997/98 El Nino.
http://i35.tinypic.com/dzdkqo.jpg
At the same time, June 2000, the average Subsurface Temperature of the equatorial Pacific (a better proxy for OHC) is also at the level it was at before the El Nino.
http://i37.tinypic.com/2yy1mpf.jpg
So in that short view, it looks as though that El Nino actually contributed to the rise in OHC of the Pacific from 1996 to 2000. It’s counterintuitive, but that’s what it looks like.
JFA in Montreal: You asked, “Can’t the author at least mention once what does mean ENSO and SST and any other jargon-ish acronym?”
The author is usually good about that, but this time, apparently, he forgot.
ENSO = El Nino-Southern Oscillation
SST = Sea Surface Temperature
NINO3.4 = Area of the equatorial Pacific with the coordinates of 5S-5N, 170W-120W. The SST anomalies of that area correlate well with the linear response of global temperatures to El Nino events.
No way..too dizzy..la Nina has to come back with her light blue dress!
Robert A Cook PE (13:25:06) : Why was 1998’s global temperatures higher than before?
Consider the following series of events:
1989-1992.Sevensmark opens his clouds’ window over the pacific ocean. (low peak in GCR-The Chilling Stars p.77)
1989 As predicted by Shirley, based on SIM:James Shirley:An unusual “solar event” will take place in the years 1990-1992″
1989 March and September Big solar CME, Quebec black out.
1997-1998 Big El Nino, pacific ocean begins cooling (heat emission).
Basil: “So do you have a theory as to where all this heat, or energy, came from? It just comes “out of nowhere” with the “super” El Nino of 97-98, and then is distributed latitudinally in the years to follow. But where did it come from?”
The riddle of the decade, that one is.
The Southern Ocean feeds the equatorial Pacific through the Humboldt Current, and it appears that the SST anomalies of the Southern Ocean may have added the boost for the significant El Ninos that started with the 1972/73 El Nino and ended (we can hope) with the 1997/98 El Nino.
http://i39.tinypic.com/2qch20w.jpg
There was a substantial decrease in cloud amount over the tropical Pacific in 1995.
http://bobtisdale.blogspot.com/2009/04/did-decrease-in-total-cloud-amount-fuel.html
The volcanic aerosols from Mount Pinatubo should also have dissipated by then, but that’s usually depicted as a gradual decline.
But as you’ve said, in watching the SSH anomaly animation, the fuel in the PWP just seems to appear out of nowhere in September 1996.
And that video is SSH, not SST, so it should be capturing subsurface anomalies as well.
What happened when the Mount Pinatubo volcanic ash returned to the ocean? The Mount Pinatubo ash dropped primarily into the PWP.
http://en.wikipedia.org/wiki/File:Tephra_fall_from_1991_eruption_of_Mt_Pinatubo.gif
Did it change the ocean optics for a couple of years, causing heat to accumulate over a short period of time? One would think ocean currents would distribute it, but gyres would return it over time if it remained in the photic zone.
Jonathan Baxter: You wrote, “But what causes the post-El-Nino heating? The heat has to come from somewhere. Climate scientists would presumably argue that it is the result of gradual heating caused by radiative imbalance due at least in part to human GHGs. Given the complex cycles-within-cycles of the climate system, one would not necessarily expect the SST to smoothly track the increase in CO2.”
Apparently you didn’t go to the posts linked to Notes 5 and 6. If you had, you would not have posted your comment. Those posts illustrate and discuss the processes of heat distribution within the Pacific and the troposphere.
Regards
Robert A Cook: “Where did the 1998 El Nino come from (what was the cuase of the El Nino?), and what was the source of energy for that El Nino?”
The 1997/98 El Nino was not that unusual. The 1982/83 El Nino had a comparable peak SST anomaly, but its heat distribution was suppressed by the eruption of El Chichon. And the 1972/73 El Nino was not that much smaller than the other two. Here’s a comparison graph of the ERSST.v3 and HADSST versions of NINO3.4 SST anomalies.
http://i41.tinypic.com/fk4eaf.jpg
And if we consider the length of the 1986/87/88 El Nino, it wasn’t that much different than the others.
Also, scroll up to my 14:37:52 reply to Basil for a further discussion of the 1997/98 El Nino.
as of 8/17 El Nino is looking awfully weak:
http://www.osdpd.noaa.gov/data/sst/anomaly/2009/anomnight.8.17.2009.gif
and looking at that psychedelic graph, I’d say we are heading back neutral or Nina
by winter.
Gotta-put-on-some-Grateful Dead….
Jonathan Baxter: And the sentence you quoted, “Climate scientists attempt to attribute the residual to anthropogenic causes, when it is clearly a result of significant El Nino events,” was dependent on the sentence that preceeded it. In other words, you took it out of context. The entire paragraph above read:
As illustrated in this post and in those linked, that residual accounts for most if not all of the global TLT and SST warming since the late 1970s. Climate scientists attempt to attribute the residual to anthropogenic causes, when it is clearly a result of significant El Nino events.
Basil (10:37:56) “So do you have a theory as to where all this heat, or energy, came from? It just comes “out of nowhere” with the “super” El Nino of 97-98, and then is distributed latitudinally in the years to follow. But where did it come from?”
Check out the cloud cover graphs here:
http://www.appinsys.com/GlobalWarming/TropicalSST.htm
–
Bob, it would be interesting to see those hovmollers with the annual cycle removed. (That would further accent the abruptness of the step.) Nice work.
JFA: Click on the Glossary tab for an explanation of the abbreviations used on this site.
From Bob Tisdale’s blog:
“Note how there was an increase in SST anomaly trend but a decrease in trend for the Total Cloud Amount anomalies.”
http://i44.tinypic.com/358tgxx.jpg
http://bobtisdale.blogspot.com/2009/04/did-decrease-in-total-cloud-amount-fuel.html
Nice work Bob.