Cross-Sectional Views of Three Significant El Ninos – Part 2

I’ve moved to WordPress.  This post can now be found at Cross-Sectional Views of Three Significant El Ninos – Part 2

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The following is the video “Cross-Sectional Views of Three Significant El Ninos – Part 2”. It includes the 1982/83 and the 1986/87/88 El Nino events. The post Cross-Sectional Views of Three Significant El Nino Events – Part 1 covers the 1997/98 El Nino.

A QUICK SUMMARY

The 1982/83 El Nino was similar in magnitude to the 1997/98 El Nino, but during the 1982/83 El Nino, the Thermocline in the Indian Ocean did NOT “flatten” as it had in the 1997/98 El Nino, so the anomalous warming in the Western equatorial Indian Ocean did not occur during the 1982/83 El Nino. The Pacific Thermocline did flatten during the 1982/83 El Nino, just as it had during the 1997/98 event.

During the 1986/87/88 multiyear El Nino, the Pacific Thermocline does not flatten completely, but there is a noticeable decrease in its slope. The Pacific Thermocline remains “flatter than normal” until a month or two before the secondary peak of 1986/87/88 El Nino.

Climate Modelers Reproduce Early 20th Century Warming With The Help Of Outdated Solar Forcings

I’ve moved to WordPress.  This post can now be found at Climate Modelers Reproduce Early 20th Century Warming With The Help Of Outdated Solar Forcings

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INITIAL NOTE

This is a look at the impacts of outdated TSI reconstructions used by climate modelers. The Lean et al and the Hoyt and Schatten TSI reconstructions are discussed.

INTRODUCTION

The illustration of Climate Change Attribution from the Global Warming Art website has reared its head once again. Recently, yet another AGW proponent used it to show the recent dominance of anthropogenic greenhouse gases on climate. He wrote, “Here is a graphic from an attribution study:
http://www.globalwarmingart.com/wiki/Image:Climate_Change_Attribution_png
“Do note that global warming (so-called greenhouse) gases dominate in recent years, in agreement with this latest field study.”

Figure 1 is a copy of the referenced illustration.

http://i39.tinypic.com/2s0o2uo.jpg
Figure 1

The blogger apparently didn’t bother to delve into the study that served as the basis for the graphic, nor did he investigate the forcings used in the study.

As discussed in AGW Proponents Are Two-Faced When It Comes To Solar Irradiance As A Climate Forcing, the study used by Global Warming Art is Meehl et al (2004). "Combinations of Natural and Anthropogenic Forcings in Twentieth-Century Climate". A link to the paper:
http://www.cgd.ucar.edu/ccr/publications/meehl_additivity.pdf

And as noted in my earlier post, the solar study referenced by Meehl et al is Hoyt and Schatten (1993) "A discussion of plausible solar irradiance variations". Yes, that’s right, 1993. Refer to Table 1 in Hoyt et al and to the discussion on page 3723 to confirm the source of solar data.

ANOTHER LOOK AT THE HOYT AND SCHATTEN TSI DATA

It is generally accepted that global temperature responds approximately 0.1 deg C as Total Solar Irradiance (TSI) varies through the solar cycle. For those who need confirmation of this, in the GISS Surface Temperature Analysis, Global Temperature Trends: 2007 Summation, they wrote, “This cyclic solar variability yields a climate forcing change of about 0.3 W/m2 between solar maxima and solar minima. (Although solar irradiance of an area perpendicular to the solar beam is about 1366 W/m2, the absorption of solar energy averaged over day and night and the Earth's surface is about 240 W/m2.) Several analyses have extracted empirical global temperature variations of amplitude about 0.1°C associated with the 10-11 year solar cycle, a magnitude consistent with climate model simulations, but this signal is difficult to disentangle from other causes of global temperature change, including unforced chaotic fluctuations.”
http://data.giss.nasa.gov/gistemp/2007/
I’ll replay the quote again later.

In this post, TSI has been scaled so that the variations in the solar cycle reflect a global temperature variation of approximately 0.1 deg C for the past three cycles.

Figure 2 is a comparative graph of two TSI reconstructions after they’ve been scaled to reflect their impacts on Global Temperature anomaly. The blue curve marked Svalgaard is based on the current understanding of TSI variations, while the purple curve uses the Hoyt and Schatten TSI reconstruction data employed by Meehl et al. The data begins in 1880, the first year of GISS and NCDC global temperature indices. The final year, 1979, was dictated by the availability of the Hoyt and Schatten data.
http://s5.tinypic.com/e7i71l.jpg
Figure 2

Note how the Hoyt and Schatten TSI reconstruction would impose an approximate 0.19 deg C/Century erroneous linear trend on global temperature. (0.19 deg C/Century is the difference between the Hoyt and Schatten and the Svalgaard trends.)

In their “Frequently Asked Question 3.1 - How are Temperatures on Earth Changing?” of AR4, the IPCC states that global “surface temperatures have in­creased by about 0.74°C over the past hundred years.” Link to IPCC reference:
http://www.gcrio.org/ipcc/ar4/wg1/faq/ar4wg1faq-3-1.pdf

Figure 3 is the top half of FAQ 3.1 Figure 1 of the IPCC supplement.
http://s5.tinypic.com/vowo7c.jpg
Figure 3

The use of the Hoyt and Schatten data wrongly accommodates 26% of that rise (0.19 deg C/Century divided by 0.74 deg C/Century).

Basically, modelers use outdated data in failed attempts to duplicate the rise in global temperatures during the early part of the 20th Century, Figure 4.
http://s5.tinypic.com/30nf0rb.jpg
Figure 4

THE SAME HOLDS TRUE FOR MODELS THAT USE THE LEAN et al RECONSTRUCTION

In Figure 5, the linear trends of the Lean at al and Svalgaard TSI reconstructions (Scaled to Global Temperature Anomaly Impact) are compared. The data starts in 1880 again, and the Lean et al reconstruction ended in 1999, so the graph covers this period. As illustrated, the use of Lean et al by climate modelers would erroneously add approximately 0.14 deg C/Century to the model’s linear trend.
http://s5.tinypic.com/2drrspy.jpg
Figure 5

And again, it’s an attempt to replicate the rise in global temperature anomaly during the early part of the 20th Century. Refer to Figure 6.
http://s5.tinypic.com/2e5mcds.jpg
Figure 6

And what GCM uses the Lean et al TSI reconstruction to hindcast global temperature anomalies from 1880 to 2003?

The GISS Model E.

Refer to Hansen et al, 2007, “Climate simulations for 1880–2003 with GISS modelE”, “Climate Dynam.”, 29, 661-696, doi:10.1007/s00382-007-0255-8. (Note that the first pdf file is ~24MB.)http://pubs.giss.nasa.gov/docs/2007/2007_Hansen_etal_3.pdfSupplemental Information:http://pubs.giss.nasa.gov/docs/2007/2007_Hansen_etal_3_supplement.pdf

The radiative forcings used are discussed and documented by GISS here:http://data.giss.nasa.gov/modelforce/http://data.giss.nasa.gov/modelforce/RadF.txt

Figure 7 is a graph of the Solar Forcing from the above GISS Global Mean Effective Forcing link. There’s no mistaking the Lean et al curve.
http://i33.tinypic.com/2it625e.jpg
Figure 7

BUT A CURIOUS THING HAPPENS AFTER THE SOLAR FORCING DATA IS INPUT TO THE GISS MODEL E

On one hand, as noted above, GISS states, “Several analyses have extracted empirical global temperature variations of amplitude about 0.1°C associated with the 10-11 year solar cycle, a magnitude consistent with climate model simulations…”

Yet the output of the Model E with only Solar forcings does not reflect that.
http://s5.tinypic.com/s6m71z.jpg
Figure 8

And climatologists wonder why people are skeptical of climate models!

TO DOWNLOAD THE SOLAR ONLY MODEL E OUTPUT

Follow the links to the data used to create the GISS output data for Figure 8:

In the following, select “Lat-Time” in “Table 1”, “2 Miscellaneous Forcings,” “Solar irradiance.”
http://data.giss.nasa.gov/modelE/transient/climsim.html

Set the “Mean Period” in the following link to “1” (one month) and “Output” to “formatted page w/ download links”:
http://data.giss.nasa.gov/modelE/transient/Rc_jt.1.06.html

Then click on the “text file” link within the group of links marked “Download the global mean plot as PDF, Postscript, or text file” on the resulting “DATASETS AND IMAGES” page:

You’ll then have to convert the monthly data to annual means.

FURTHER COMMENTS ABOUT THE GISS MODEL E

Refer to the following two posts for additional discussions on the GISS Model E hindcasts:
http://bobtisdale.blogspot.com/2008/09/giss-model-e-climate-simulations.html
http://bobtisdale.blogspot.com/2008/09/giss-model-e-climate-simulations-part-2.html

SOURCE OF TSI RECONSTRUCTION DATA

TSI reconstruction and composite data is available from Leif Svalgaard:http://www.leif.org/research/TSI%20(Reconstructions).xls

The Impact of the North Atlantic and Volcanic Aerosols on Short-Term Global SST Trends

I’ve moved to WordPress.  This post can now be found at The Impact of the North Atlantic and Volcanic Aerosols on Short-Term Global SST Trends

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PRELIMINARY NOTE

I took this post from the prior one “A Secondary (Repeated) ENSO Signal?” and added to the narrative because it is worthy of its own post. I’ve also added long-term trend comparisons at the end to illustrate a point.

INTRODUCTION
I prepared a post on SST trends for the globe, Figure 1, and for individual ocean subsets. (That post has now been put to the side.)
http://s5.tinypic.com/24f0j8x.jpg
Figure 1

The disparity between the North Atlantic SST anomaly trend, Figure 2, and the rest of the subsets was striking. The North Atlantic SST anomaly linear trend for the period of November 1981 (the start of the OI.v2 SST dataset) and January 2009 is ~0.264 deg C/decade, while the global linear trend is ~0.0948 deg C/decade. The North Atlantic linear trend is approximately 2.8 times the global linear trend, driven by Atlantic Meridional Overturning Circulation and El Ninos, (yes, El Ninos).
http://s5.tinypic.com/x23xis.jpg
Figure 2

NOTE: El Nino-induced step changes in the North Atlantic were illustrated in the post There Are Also El Nino-Induced Step Changes In The North Atlantic. Recall, also, that the Atlantic Meridional Overturning Circulation appears to be impacted by ENSO events as well. Refer to the post titled Atlantic Meridional Overturning Circulation Data.

REMOVING THE NORTH ATLANTIC DATA

So I decided to remove the North Atlantic SST anomaly data from the global. There is no simple way to do this with a coordinate-based system such as NOMADS or KNMI Climate Explorer, so I made an assumption. The Atlantic Ocean surface area is approximately 30% of the global ocean surface area, and I assumed the North Atlantic represented 50% of that. I then scaled the North Atlantic SST anomaly data by 0.15 and subtracted it from the global SST anomalies. The resulting dataset, noted as “Global SST Anomalies Without North Atlantic,” is illustrated in Figure 3. There isn’t a significant difference between the peaks and troughs of this adjusted dataset and those of the global SST anomalies. Visually, the curve appears as though it's been rotated. What stands out, however, is the decrease in trend to 0.0546 deg C/decade.
http://s5.tinypic.com/2ihuot0.jpg
Figure 3

REMOVING THE EFFECTS OF VOLCANIC AEROSOLS

Volcanic aerosols lower the SST anomalies at the time of the eruption and for a few years afterwards, so SSTs would have dropped as a result of the 1982 El Chichon and 1991 Mount Pinatubo eruptions. This increased the trend over the term of the dataset. Figure 4 is a comparative graph of the “Global SST Anomalies Without North Atlantic” and inverted Sato Index of Stratospheric mean optical thickness. I’ll use the Sato Index data to remove the impacts of the volcanic eruptions.
http://s5.tinypic.com/4r5f8y.jpg
Figure 4

If we consider that the peak of the decrease in global land plus sea surface temperature caused by the Mount Pinatubo eruption is considered to be between 0.2 to 0.5 deg C, the 0.15 deg C illustrated at 1991 would be toward the conservative side for SST. Eyeballing it, it appears to be in line, so there doesn’t seem to be any need to scale the Sato Index data. I then added the Sato Index to the “Global SST Anomalies Without North Atlantic” data. The resulting changes in the “Global SST Anomalies Without North Atlantic” data is shown in Figure 5. Note how the trend has decreased to 0.036 deg C/decade.
http://s5.tinypic.com/al1yth.jpg
Figure 5

LONG-TERM SST DATA

Figures 6 and 7 are long-term comparisons of global SST anomaly data and the global SST anomaly data with the North Atlantic and the effects of volcanic aerosols removed. Figure 6 uses ERSST.v2 SST anomaly data and Figure 7 uses HADISST SST anomaly data. I used the same scaling factors that I used in the short-term data. All datasets have been smoothed with 37-month filters (but the trends were determined from the unsmoothed data, which is why the trend lines extend beyond the smoothed curves). For ERSST.v2 Global SST anomaly data, the linear trend from January 1880 to January 2009 is approximately 0.040 deg C/decade, but with the North Atlantic and volcanic aerosols removed, the linear trend drops to approximately 0.033 deg C/decade. A similar drop results with the HADISST SST anomaly data, with the Global SST anomaly linear trend dropping from 0.041 deg C/decade to 0.035 deg C/decade when the North Atlantic and volcanic aerosols are removed. Note that over the period of 1880 to 2008 there is no significant change in the trends caused by volcanic aerosols. The Mount Pinatubo and Krakatau eruptions were approximately the same magnitudes, both had a DVI of 1,000, so they would tend to “balance” one another at opposite ends of the period.
http://s5.tinypic.com/2mrvfyx.jpg
Figure 6
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http://s5.tinypic.com/2q0vhj4.jpg
Figure 7

A CLOSING NOTE ABOUT TRENDS

The Global SST anomaly trend from November 1981 to January 2009 is approximately 0.0948 deg C/ decade or 0.95 deg C/century. Without the natural variations in North Atlantic SST anomalies and without the impacts of two significant volcanic eruptions, the SST trend would project out to a rise of only 0.36 Deg C over the next 100 years, which is more in line with the long-term trends.

Figure 8 is the upper half of “FAQ 3.1, Figure 1” from the IPCC’s “Frequently Asked Question 3.1 - How are Temperatures on Earth Changing?”
http://www.gcrio.org/ipcc/ar4/wg1/faq/ar4wg1faq-3-1.pdf

The caption reads, “Note that for shorter recent periods, the slope is greater, indicating accel­erated warming. The blue curve is a smoothed depiction to capture the decadal variations. To give an idea of whether the fluctuations are meaningful, decadal 5% to 95% (light grey) error ranges about that line are given (accordingly, annual values do exceed those limits). Results from climate models driven by estimated radiative forcings for the 20th century (Chapter 9) suggest that there was little change prior to about 1915, and that a substantial fraction of the early 20th-century change was contributed by naturally oc­curring influences including solar radiation changes, volcanism and natural variability. From about 1940 to 1970 the increasing industrialisation following World War II increased pollution in the Northern Hemisphere, contributing to cooling, and increases in carbon dioxide and other greenhouse gases dominate the observed warming after the mid-1970s.”
http://s5.tinypic.com/vowo7c.jpg
Figure 8

Are the IPCC taking advantage of the natural cycles of Atlantic Meridional Overturning Circulation and of periodic volcanic eruptions to illustrate “ACCELERATED WARMING” in more recent decades?

Of course they are!

SOURCES

OI.v2 SST data can be accessed through the NOAA NOMADS system:
http://nomad3.ncep.noaa.gov/cgi-bin/pdisp_sst.sh?lite

ERSST.v2 data and HADISST data can be accessed through the KNMI Climate Explorer website:
http://climexp.knmi.nl/selectfield_obs.cgi?someone@somewhere

The Sato Index Data is available from GISS at:
http://data.giss.nasa.gov/modelforce/strataer/
Specifically:
http://data.giss.nasa.gov/modelforce/strataer/tau_line.txt

A Secondary (Repeated) ENSO Signal?

I’ve moved to WordPress.  This post can now be found at A Secondary (Repeated) ENSO Signal?

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CORRECTION: In agreement with my post The Atlantic Multidecadal Oscillation - Correcting My Mistake, I edited the sentence in this post that read, “The disparity between the North Atlantic SST anomaly trend, Figure 2, and the rest of the subsets was striking, which is one of the reasons why North Atlantic SST is normally illustrated as a residual, the Atlantic Multidecadal Oscillation.” The AMO is not a residual. It is detrended North Atlantic SST anomalies, according to the NOAA ESRL. I therefore deleted, “which is one of the reasons why North Atlantic SST is normally illustrated as a residual, the Atlantic Multidecadal Oscillation.”
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PRELIMINARY NOTE

In the following, I’ve removed the Atlantic Ocean SST anomalies from the global SST anomalies, then removed the effects of volcanic aerosols and ENSO. The result was an unexpected secondary or repeated ENSO signal. This secondary ENSO signal would appear if the Atlantic Ocean SST anomalies remained, but the Atlantic skews the trend so significantly that it might be best to evaluate the secondary ENSO without it.

This post was originally intended to illustrate the influence of the North Atlantic on recent SST anomaly trends. It gets sidetracked with the new find. Because the new phenomenon subtracts from the original intent, I’ll repeat the first part of this post in a second one.

I offer no basis for this secondary ENSO signal? Is it a result of cloud feedback? Is it caused by some effect of lingering atmospheric and oceanic Rossby and Kelvin waves initiated by the El Nino? Or is it a result of the scaling factors I’ve used?

As with many of my posts, someone with a better grasp of statistical tools could select coefficients and scaling factors that are more refined and, with those tools, could perform a better analysis. I accept that and welcome additional research into what I present here. In that respect, consider this a preview. But I ask those who do follow-up on this to present your results with simple time-series graphs. Remember, also, to cite this blog and its author.

And for those who would like to research this but have never downloaded OI.v2 SST data, I’ve included instructions for downloading the data at the end of this post.

Regards.

INTRODUCTION

I prepared a post on SST trends for the globe, Figure 1, and for individual ocean subsets. (That post has now been put to the side.)
http://s5.tinypic.com/24f0j8x.jpg
Figure 1

The disparity between the North Atlantic SST anomaly trend, Figure 2, and the rest of the subsets was striking. The North Atlantic SST anomaly trend for the period of November 1981 (the start of the OI.v2 SST dataset) and January 2009 is ~0.264 deg C/decade, while the global trend is ~0.0948 deg C/decade. The North Atlantic trend is approximately 2.8 times the global trend, driven by Atlantic Meridional Overturning Circulation and El Ninos, (yes, El Ninos).
http://s5.tinypic.com/x23xis.jpg
Figure 2

NOTE: El Nino-induced step changes in the North Atlantic were illustrated in the post There Are Also El Nino-Induced Step Changes In The North Atlantic. Recall, also, that the Atlantic Meridional Overturning Circulation appears to be impacted by ENSO events as well. Refer to the post titled Atlantic Meridional Overturning Circulation Data.

REMOVING THE NORTH ATLANTIC DATA

So I decided to remove the North Atlantic SST anomaly data from the global. There is no simple way to do this with a coordinate-based system such as NOMADS or KNMI Climate Explorer, so I made an assumption. The Atlantic Ocean surface area is approximately 30% of the global ocean surface area, and I assumed the North Atlantic represented 50% of that. I then scaled the North Atlantic SST anomaly data by 0.15 and subtracted it from the global SST anomalies. The resulting dataset, noted as “Global SST Anomalies Without North Atlantic,” is illustrated in Figure 3. There isn’t that much difference between the peaks and troughs of this adjusted dataset and those of the global SST anomalies. In term of visual effect, the curve appears to have been rotated, decreasing the trend to 0.0546 deg C/decade.
http://s5.tinypic.com/2ihuot0.jpg
Figure 3

REMOVING THE EFFECTS OF VOLCANIC AEROSOLS

Volcanic aerosols lower the SST anomalies at the time of the eruption and for a few years afterwards, so SSTs dropped as a result of the 1982 El Chichon and 1991 Mount Pinatubo eruptions. This increased the trend over the term of the dataset. Figure 4 is a comparative graph of the “Global SST Anomalies Without North Atlantic” and inverted Sato Index of Stratospheric mean optical thickness. I’ll use the Sato Index data to remove the impacts of the volcanic eruptions.
http://s5.tinypic.com/4r5f8y.jpg
Figure 4

Eyeballing it, there didn’t appear to be any need to scale the Sato Index data, so I added the Sato Index data to the “Global SST Anomalies Without North Atlantic” data. The resulting changes in the “Global SST Anomalies Without North Atlantic” data is shown in Figure 5. Note how the trend has decreased to 0.036 deg C/decade.
http://s5.tinypic.com/al1yth.jpg
Figure 5

A NOTE ABOUT THE TRENDS

Without the North Atlantic and without the impacts of two significant volcanic eruptions, the SST trend would extend out to a rise of only 0.36 Deg C over the next 100 years. If GCMs were “tuned” without considering these effects, the rise in global temperature over the next century is bound to fall short of their projections.

BACK TO THE ADJUSTED DATA

Note also that the curve resembles NINO3.4 SST anomalies. Refer to Figure 6, which is a comparative graph of scaled NINO3.4 SST anomalies and the “Global SST Anomalies Without North Atlantic” after the effects of volcanic aerosols have been removed. They correlate well and the timing of the rises and the peaks do not appear to have any significant lags.
http://s5.tinypic.com/344r2f4.jpg
Figure 6

REMOVING THE EFFECTS OF EL NINO PRESENTS A CURIOSITY

The next obvious step was to remove the NINO3.4 SST anomaly impact from the “Global SST Anomalies Without North Atlantic and With Volcanic Aerosols Removed” data. In this step, I simply subtracted the scaled NINO3.4 SST anomalies from the other dataset. Refer to Figure 7, which is a graph of the “Global SST Anomalies Without North Atlantic” in which both the volcanic aerosols AND ENSO impacts have been removed. A curiosity resulted. A “secondary El Nino” signal appears 8 months after the November 1997 peak of the 1997/98 El Nino.
http://s5.tinypic.com/5v50s9.jpg
Figure 7

NOTE

THE SCALING FACTORS I’VE USED ARE “IN THE BALLPARK” OF REALITY, BUT THIS “SECONDARY EL NINO” SIGNAL MAY SIMPLY BE A PRODUCT OF THE SCALING FACTORS AND WEIGHTING I USED. IT DOES, HOWEVER, NEED TO BE INVESTIGATED FURTHER. INCREASING THE NINO3.4 SST ANOMALY SCALING FACTOR BEFORE REMOVING ITS IMPACT FROM THE “ADJUSTED GLOBAL” DATA WILL OBVIOUSLY DECREASE THE “SECONDARY EL NINO” SIGNAL, AND VICE VERSA.

Back to the post.

A QUICK LOOK FOR THE SOURCE OF THE “SECONDARY EL NINO” SIGNAL

The global temperature anomaly mapping feature at the GISS website can be modified so that it only presents SST anomalies. GISS uses OI.v2 SST data from December 1981 to present, the same source used in this post.
http://data.giss.nasa.gov/gistemp/maps/
I changed the base period to 1971-2000, the same as the OI.v2 SST anomaly data, set the smoothing for 250km, and selected July 1998, 8 months after the November 1997 peak of the 1997/98 El Nino. Refer to Figure 8. A hot spot appears in the vicinity of the Kuroshio Extension (32N-38N, 142E-180E).
http://s5.tinypic.com/dh6e8n.jpg
Figure 8

NOTES ABOUT THE KUROSHIO EXTENSION AND THE “SECONDARY EL NINO” SIGNAL

Figure 9 is a graph of the SST anomalies for the Kuroshio Extension. As you’ll note, while the Kuroshio Extension SST anomalies are elevated (they acquire an upward step after the 1997/98 El Nino) in July 1998, they do not drop as the “secondary El Nino” signal does. In fact, the Kuroshio Extension SST anomalies do not peak until October 1999 (the spike in 1999), two years after the peak of the 1997/98 El Nino. Also, Mercator projections, and similar maps, visually distort the importance of high latitudes. So the Kuroshio Extension anomaly is a contributor to the “secondary El Nino” signal, but not the major factor. There are other areas of noticeably elevated SSTs, the Pacific Warm Pool and the South Atlantic. The Pacific Warm Pool does increase in temperature during La Ninas, but I can’t say whether the same holds true for the South Atlantic.
http://s5.tinypic.com/2wmkwn4.jpg
Figure 9

One of the reasons is that the 1982/83 and 1997/98 El Nino had different characteristics. The decline of the 1982/83 El Nino is flatter, taking longer, than the 1997/98 El Nino. Refer to Figure 10. The 1982/83 El Nino was also suppressed by the El Chichon eruption. (I borrowed Figure 10 from a prior post. This is why the 1986/87/88 El Nino data appears in it.)
http://s5.tinypic.com/2eob5fr.jpg
Figure 10

A FINAL COMPARISON

In Figure 11, the scaled NINO3.4 SST anomalies have been lagged 8 months. The NINO3.4 data correlates well with the “Global SST Anomalies Without North Atlantic With Volcanic Aerosols AND ENSO Impacts Removed”. The step changes in the “Adjusted Global” dataset after the 1986/87/88 and 1997/98 El Nino events also stand out.
http://s5.tinypic.com/1zvtn5c.jpg
Figure 11

Figure 12 illustrates the “Adjusted Global” SST anomalies in which the North Atlantic and the volcanic aerosols, ENSO, and “Secondary ENSO” impacts have been removed. Fine tuning the scaling factors would impact the shape of that curve, but it would be futile for me to adjust them without cause. That’s where you the reader take over this analysis.
http://s5.tinypic.com/2it3nyw.jpg
Figure 12

AS AN AFTERTHOUGHT

What remains (Figure 12) would include the effects of the North Atlantic on the remainder of the oceans. The step changes in the East Indian and West Pacific Oceans would also have to be accounted for.

DOWNLOADING OI.v2 SST ANOMALY DATA

The source of the SST anomaly data is the NOAA NOMADS system. Refer to the following link.
http://nomad3.ncep.noaa.gov/cgi-bin/pdisp_sst.sh?lite

Under “Control File”, select “monoiv2.ctl…Monthly OIv2 SST” and under “Plot Type”, select “time series”. Click on “Next Page”.

For “Field”, select “ssta *OIV2 SST monthly anomaly (C) rel to 1971-2000. The “Initial Time” and “Final Time” are automatically set for the first and last month of the dataset. Input the desired latitudes and longitudes. (South Latitudes and West Longitudes are negative numbers and the “From” must be less than “To”.) The default latitudes and longitudes are global, obviously. Click on “Plot” and a new window will appear.

Scroll down and click on the link for the text file. The first four global SST anomalies and header should be…

*******

data from 00Z01NOV1981 to 00Z01JAN2009
"----------"
-0.112563
-0.061554
-0.0207861
-0.0803312

*******

Obviously, if you’ve selected different start and end months, the header and initial data will change.

The coordinates used in this post, in addition to global, are:
North Atlantic = 0 to 65N and 78W to 20E
NINO3.4 = 5S to 5N and 170W to 120W
Kuroshio Extension = 32N to 38N and 142E to 180E

SATO INDEX DATA SOURCE

The Sato Index Data is available from GISS at:
http://data.giss.nasa.gov/modelforce/strataer/
Specifically:http://data.giss.nasa.gov/modelforce/strataer/tau_line.txt

Equatorial Currents Before, During, and After The 1997/98 El Nino

I’ve moved to WordPress.  This post can now be found at Equatorial Currents Before, During, and After The 1997/98 El Nino

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INTRODUCTION

Most discussions of El Nino events center primarily on Sea Surface Temperature anomalies. Sometimes they include descriptions of surface (trade) winds. Rarely do they include illustrations of surface currents, but the changes in surface currents are a significant part of ENSO because they help show the transport of warm water from the West Pacific Warm Pool to the East Equatorial Pacific. This post illustrates the surface currents before, during, and after the 1997/98 El Nino event. The changes are significant and obvious.

SOURCE OF SURFACE CURRENT ILLUSTRATIONS

I recently found a NASA educational website called “Ocean Motion and surface currents”.
http://oceanmotion.org/index.htm
Lesson 4 for students is called “Global Ocean Warming”.
http://oceanmotion.org/guides/ow_4/ow_student_4.htm
I then discovered what they called their “Ocean Surface Current Data Visualizer”.
http://oceanmotion.org/html/resources/oscar.htm
By selecting the Regions (W Eq Pacific, Cen Eq Pacific, E Eq Pacific), the Parameter (Direction) and the Months and Years, I prepared the maps used in the post and video.

REGIONS ILLUSTRATED

Figure 1 shows the locations of the three Equatorial Pacific Surface Current Maps (Western, Central, and Eastern) provided by the “Ocean Surface Current Data Visualizer”. There is a significant overlap between the Central and Eastern regions.

http://s5.tinypic.com/of0d1t.jpg
Figure 1

OCTOBER 1996 – BEFORE THE 1997/98 EL NINO

Figures 2, 3, and 4 illustrate the color-coded surface currents for the Western, Central, and Eastern Equatorial Pacific on October 1, 1996. Eastward currents are shown in blue, while westward currents are shown in a color that I’ll call khaki, for lack of a better word. The eastward (blue) current is the Equatorial Pacific Counter Current. North and South of it are the westward (khaki) North and South Pacific Equatorial Currents. In these illustrations, the South Pacific Equatorial Current appears to be the largest of the three. The NINO3.4 SST anomaly for October 1996 was neutral (-0.299 deg C, based on ERSST.v2 data).

West Equatorial Pacific – October 1996
http://s5.tinypic.com/a4n86c.jpg
Figure 2
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Central Equatorial Pacific – October 1996

http://s5.tinypic.com/5a2b8k.jpg
Figure 3
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East Equatorial Pacific – October 1996

http://s5.tinypic.com/2ronuww.jpg
Figure 4

JULY 1997 – DURING THE 1997/98 EL NINO

Between October 1996 and July 1997, the trade winds had relaxed, two Kelvin waves had traveled east across the Equatorial Pacific, and warm water that was once “contained” by the West Pacific Warm Pool has been “sloshing” east. By July 1997, the NINO3.4 SST anomalies had risen to 1.84 deg C. And as illustrated in Figures 5, 6, and 7, the Pacific Equatorial Counter Current had expanded significantly, an indication that eastward flow from the West Pacific Warm Pool to the Eastern Equatorial Pacific had, in fact, increased.

West Equatorial Pacific – July 1997

http://s5.tinypic.com/xofcj5.jpg
Figure 5
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Central Equatorial Pacific – July 1997
http://s5.tinypic.com/2mws6dv.jpg
Figure 6
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East Equatorial Pacific – July 1997
http://s5.tinypic.com/2v8mxs4.jpg
Figure 7

NOVEMBER 1997 – THE PEAK OF THE 1997/98 EL NINO

The NINO3.4 SST anomaly had risen to 2.79 deg C. The flow in the Pacific Equatorial Counter Current remained at high levels. Refer to Figures 8, 9, and 10.

West Equatorial Pacific – November 1997

http://s5.tinypic.com/2wdymog.jpg
Figure 8
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Central Equatorial Pacific – November 1997

http://s5.tinypic.com/2mnf5p2.jpg
Figure 9
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East Equatorial Pacific – November 1997

http://s5.tinypic.com/2vjapvn.jpg
Figure 10

FEBRUARY 1998 – A FEW MONTHS AFTER THE PEAK OF THE 1997/98 EL NINO

By February 1998, NINO3.4 SST anomalies had dropped by more than 0.6 deg C to 2.16 deg C. The high Pacific Equatorial Counter Current flow rates had subsided as illustrated in Figures 11, 12, and 13.

West Equatorial Pacific – February 1998

http://s5.tinypic.com/2w4cx9l.jpg
Figure 11
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Central Equatorial Pacific – February 1998
http://s5.tinypic.com/2ak0hv6.jpg
Figure 12
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East Equatorial Pacific – February 1998

http://s5.tinypic.com/65y0dk.jpg
Figure 13

JULY 1998 – THE SECOND MONTH OF LA NINA SST ANOMALIES

In July 1998, NINO3.4 SST anomalies had reached -1.14 deg C. The Pacific Equatorial Counter Current is still at extremely low levels. Refer to Figures 14, 15, and 16.

West Equatorial Pacific – July 1998

http://s5.tinypic.com/zvqwcy.jpg
Figure 14
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Central Equatorial Pacific – July 1998

http://s5.tinypic.com/f9p6v4.jpg
Figure 15
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East Equatorial Pacific – July 1998

http://s5.tinypic.com/mw7ic5.jpg
Figure 16

A FILM ILLUSTRATING THE CHANGES IN FLOW

The following film illustrates the abrupt changes in the size of the Pacific Equatorial Counter Current at the beginning and end of the 1997/98 El Nino. Note that the two surges in eastward flow that are visible in the West Equatorial Pacific maps appear to coincide with the two Kelvin waves that preceded the 1997/98 El Nino. I’ll address this in another post.

What Causes Sea Surface Temperature (SST) To Rise?

I’ve moved to WordPress.  This post can now be found at What Causes Sea Surface Temperature (SST) To Rise?

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THE SOURCE OF ENERGY NECESSARY TO RAISE SSTs

I was recently asked by a blogger at another website, “What is the source of the energy necessary to raise SSTs?”

The ultimate source of energy necessary to raise SSTs would be an increase in solar irradiance, regardless of whether the increase in solar irradiance resulted from variations in the solar cycle, or from changes in cloud cover, or from a reduction in stratospheric volcanic aerosols. The impact of shortwave radiation (visible light) on SST depends on factors such as the turbidity of the water and sea surface albedo, which in turn depends on other variables including wind speed and chlorophyll concentration. Additionally, an increase in downward longwave (infrared) radiation would warm the top few centimeters of the oceans, and through mixing caused by waves and wind stress turbulence, would warm the mixed layer of the ocean. This in turn would affect the temperature gradient between the mixed layer and skin, dampening the outward flow of heat from the ocean to the atmosphere.

Since Total Solar Irradiance does not vary significantly, it is represented that the increase in anthropogenic greenhouse gases is, therefore, responsible for the rise in SST since the mid-1970s.

HOWEVER

There are other natural processes that can raise and lower SSTs, including Thermohaline Circulation/Meridional Overturning Circulation, upwelling, and…

ENSO EVENTS

My posts at WattsUpWithThat and here at my blog…
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
…that were supplemented by…
Supplement To “Can El Nino Events Explain All Of The Warming Since 1976?”
Supplement 2 To “Can El Nino Events Explain All Of The Warming Since 1976?”
… illustrated the step changes (increases) in the East Indian and West Pacific Ocean SST anomalies (60S-65N, 80W-180, or approximately 25 to 30% of the global ocean between 60S and 65N) that resulted from the 1986/87/88 and 1997/98 El Nino events. The step increases in the East Indian-West Pacific SST anomalies (black curve) in response to the 1986/87/88 and 1997/98 El Nino events (purple curve) are very obvious in Figure 1.

http://s5.tinypic.com/16h0tuq.jpg
Figure 1

The El-Nino Induced step changes did not occur after the 1982/83 and 1991/92 El Nino events because the El Nino heat distribution processes were suppressed by the El Chichon and Mount Pinatubo eruptions. This is why Sato Index data (green curve) appears in Figure 1 and in many of the following graphs. It’s there as a reminder of the timing of the volcanic eruptions.

WHAT CAUSES THE EAST INDIAN AND WEST PACIFIC OCEAN SST ANOMALIES TO RISE IN STEPS?

During an El Nino event, water that was below the surface of the Pacific Warm Pool is transported east. Much of it is “deposited” on the surface of the Eastern Equatorial Pacific. Then, during the subsequent La Nina, surface currents and trade winds drive the warm water west to the surface of the East Indian and West Pacific Oceans. In other words, before the El Nino, the warm water was below the surface and not included in SST measurement; then after the El Nino, the warm water was on the surface and included in the SST measurement. It’s that simple. This was illustrated and discussed in detail in the posts “Can El Nino Events Explain All of the Global Warming Since 1976?” linked above.

DO THE STEP CHANGES APPEAR IN ANY OTHER OCEAN SST ANOMALY DATASETS?

The step changes DO appear in the “global” SST anomaly dataset between 60S and 65N as shown in Figure 2:
http://i41.tinypic.com/71mbd3.jpg
Figure 2

The steps DO NOT appear in Northeast Pacific SST anomaly data, Figure 3. The Northeast Pacific SST anomalies (brown curve) vary in synch with NINO3.4 SST anomalies (purple curve):
http://i39.tinypic.com/2z5kkmh.jpg
Figure 3

They DO NOT appear in the combined Southeast Pacific and South Atlantic SST anomaly data (gray curve), Figure 4. The Southeast Pacific and South Atlantic SST anomaly data also “track” NINO3.4 SST anomalies (purple curve):
http://i39.tinypic.com/2ivehp3.jpg
Figure 4

They DO NOT appear in the Western Indian Ocean SST (bronze curve) anomaly data, though there are some lags in the responses to the La Ninas, Figure 5:
http://i40.tinypic.com/rwmers.jpg
Figure 5

However, they DO appear in the East Indian-West Pacific SST anomaly data as noted above and illustrated in Figure 1, and they DO appear in the North Atlantic SST anomaly data (red curve), Figure 6:
http://i43.tinypic.com/2ezsk92.jpg
Figure 6

In fact, the step changes in the East Indian-West Pacific SST anomaly data (green curve) are very similar in scale to those in the North Atlantic (red curve), Figure 7, even though the North Atlantic is influenced by AMOC:
http://i39.tinypic.com/15cocop.jpg
Figure 7

There are divergences between the two datasets in later years, indicating that there is an additional factor that influences North Atlantic SST anomalies--Atlantic Meridional Overturning Circulation. The divergence could also imply that the 2002/03, 2004/05, and 2006/07 El Nino events had a greater influence on the North Atlantic than they did on the East Indian and West Pacific Oceans.

The North Atlantic step changes were discussed in my post:
There Are Also El Nino-Induced Step Changes In The North Atlantic.

WHERE DO EL NINO EVENTS GET THEIR ENERGY?

The next question would logically be, Where do El Nino events get the energy necessary to raise SSTs in steps in the East Indian and West Pacific Oceans and in the North Atlantic?

As mentioned above, the source of warm water for El Nino events is the Pacific Warm Pool. William S. Kessler of the NOAA Pacific Marine Environmental Laboratory, in his webpage titled “Frequently-(well, at least once)-asked-questions about El Niño”, provides a basic description of El Nino events. Refer to:

http://faculty.washington.edu/kessler/occasionally-asked-questions.html#q1
In it, he writes, “During El Niño events, this entire system relaxes. The trade winds weaken, particularly west of the Dateline, and the piled-up water in the west sloshes back east, carrying the warm pool with it.”

AND WHERE DOES THE PACIFIC WARM POOL GET ITS SUPPLY OF WARM WATER?

The Pacific Warm Pool receives part of its supply of warm water from prior El Nino events. The warm water that was “sloshed” eastward during the el Nino is returned to the West Pacific by the Pacific Equatorial Currents. This was discussed and illustrated with a video in Recharging The Pacific Warm Pool.

The results include a step change in the Western Equatorial Pacific Warm Water Volume. It is quite visible after the 1997/98 El Nino, the blue curve in Figure 8.

http://i37.tinypic.com/28sxc8m.jpg
Figure 8

Step changes after the 1986/87/88 and 1997/98 El Nino events are also visible in The Indo-Pacific Warm Pool Index (brown curve) shown in Figure 9.
http://i41.tinypic.com/biukd5.jpg
Figure 9

And part of the recharging of the Pacific Warm Pool is simply the return to “normal” equatorial Pacific conditions following an El Nino event. This can be seen in the video included in “Cross-Sectional Views of Three Significant El Nino Events – Part 1.”

ADDITIONALLY, SHARP DECREASES IN CLOUD COVER OVER THE PACIFIC WARM POOL DURING EL NINO EVENTS ALLOW THE SUN TO WARM SSTs THERE

In “ENSO Surface Shortwave Radiation Forcing over the Tropical Pacific” (2008), Pavlakis et al illustrated the correlation between NINO3.4 SST anomalies and Downward Shortwave Radiation (visible light) anomaly (DSR-A) at the surface for the Western Pacific (10S–5N, 120–140E).
http://www.atmos-chem-phys-discuss.net/8/6697/2008/acpd-8-6697-2008-print.pdf

They further explain that the changes in Downward Shortwave Radiation are caused mostly by changes in Cloud Amount. As illustrated in Figure 10, during the 1997/98 El Nino, Downward Shortwave Radiation (black curve) rose almost 25 Watts/meter^2 as a result. During the El Nino events with lower NINO3.4 SST anomalies, the increases in Downward Shortwave Radiation were proportionately lower.
http://i41.tinypic.com/2435kbb.jpg
Figure 10

These ENSO-caused changes in cloud amount were further discussed in Recharging The Pacific Warm Pool Part 2.

UPDATE November 20, 2009: I’m in the process of writing yet another post on the multiyear aftereffects of major El Nino events, and I felt a discussion in it would add much to this post, so I’ve included it here. I've also changed the Figure numbers so that the run in sequence here.

CLOUD AMOUNT ASPECT OF ENSO RECHARGE PHASE IS DISCUSSED IN PAVLAKUS ET AL (2008)

In “ENSO Surface Shortwave Radiation Forcing over the Tropical Pacific” (2008), Pavlakis et al illustrated inverse relationship between NINO3.4 SST anomalies and Downward Shortwave Radiation (visible light) anomaly (DSR-A) at the surface for the Central and Eastern Tropical Pacific:
http://www.atmos-chem-phys-discuss.net/8/6697/2008/acpd-8-6697-2008-print.pdf

The Pavlakis et al Figure 6 is shown here as Figure 11. It compares NINO3.4 SST anomalies and Downward Shortware Radiation (DSR), which is visible light, for two areas of the Central and Eastern Equatorial Pacific. Note how when NINO3.4 SST anomalies are negative, indicating a La Nina, DSR anomalies are positive, indicating that more sunlight is reaching and entering the Central and Eastern Equatorial Pacific Ocean, warming it. The opposite happens during an El Nino: NINO3.4 SST anomalies are positive and DSR anomalies are negative, indicating that less visible light is warming the Central and Eastern Equatorial Pacific Ocean. Keep in mind that during the El Nino phase, there may be less sunlight entering the Central and Eastern Pacific Ocean, but this is happening during the discharge phase of ENSO. Then, when the El Nino fades, cloud amount drops and DSR increases, recharging the heat released during the El Nino.
http://i47.tinypic.com/eqs7d3.png
Figure 11

And some might find the Pavlakis et al Figure 1 informative. It illustrates, “The distribution of downward shortwave radiation at the surface (DSR), over the tropical and subtropical Pacific for the three month period November, December, January (NDJ); (a) eleven neutral years average, (b) average for five El Nino years, (c) average for five La Nina years.” I’ve animated the individual cells of their Figure 1 in my Figure 12. Pavlakis et al detail the source of Figure 12 (Their Figure 6) on page 4, under the heading of “Long-term surface shortwave radiation.”

http://i48.tinypic.com/2a9cxfq.gif
Figure 12
Cell a:
http://i49.tinypic.com/27ytmc8.png
Cell b:
http://i47.tinypic.com/vsmkd4.png
Cell c:
http://i49.tinypic.com/1gg07s.png

IS THERE EVIDENCE OF AN IMPACT OF ANTHROPOGENIC GREENHOUSE GASES ON THE RECHARGE MODE OF ENSO?

The next logical point to address would be how much of the ocean heat recharge during the La Nina events could be attributable to the constantly increasing infrared radiation from Anthropogenic Greenhouse Gases and how much could be attributable to the rise in visible light from the decrease in cloud amount. This unfortunately raises the debate about the impacts of infrared radiation and visible light on Ocean Heat Content. Downward Shortwave Radiation (DSR), which is visible light, penetrates and warms the ocean for 100+ meters, while infrared radiation or Downward Longwave Radiation (DLR) only penetrates the top few centimeters. So the order of magnitude of the temporary increase in DSR (visible light) is many times greater than the long-term increase in DLR (infrared radiation) from greenhouse gases. But the argument has been presented that DLR (infrared radiation), through mixing caused by waves and wind stress turbulence, would warm the mixed layer of the ocean. This in turn would impact the temperature gradient between the mixed layer and skin, dampening the outward flow of heat from the ocean to the atmosphere. The end result according to the argument: OHC would rise due to an increase in DLR (infrared radiation) caused by increases in greenhouse gas emissions.

However, refer to the Tropical Pacific OHC data, Figure 13. While there is no doubt that there is a positive trend in the Tropical Pacific OHC data, the graph shows decadal and multidecadal periods of decreasing OHC, not gradually rising OHC as one would expect if greenhouse gases had an effect on the tropical Pacific. The heat lost during these long-term decreases is replaced and additional heat is added during two multiyear periods that coincide with the multiyear La Nina events of 1973/74/75/76 and 1998/99/00. Specifically, for the decade from 1963 to 1973, OHC anomalies drop gradually from ~0.04 GJ/m^2 to ~-0.3 GJ/m^2, and for the two decades from 1977 to 1997 (1999), OHC anomalies drop gradually from ~0.16 GJ/m^2 to ~-0.12 GJ/m^2 (~-0.16 GJ.m^2). During the multiyear (4-year) period between them, from 1973 to 1977, OHC anomalies rose from ~-0.3 GJ/m^2 to ~0.16 GJ/m^2; this appears to be a recharge caused by the multiyear 1973/74/75/76 La Nina. The 1995/96 upsurge in tropical Pacific OHC was explained in McPhaden (1999) “Genesis and Evolution of the 1997-98 El Nino,” as a result of “stronger than normal trade winds associated with a weak La Nina in 1995–96.”
http://www.pmel.noaa.gov/pubs/outstand/mcph2029/text.shtml

http://i36.tinypic.com/eqwdvl.png

Figure 13

With the anomalous rise in Tropical Pacific OHC in 1995/96 shown in Figure 13, it could be argued that the rise in tropical Pacific OHC of ~-0.08 GJ/m^2 to ~0.24 GJ/m^2 from 1998 to late 2001 was a rebound to the values established by the 1995/96 La Nina, or it could be argued that the rise in tropical Pacific OHC was caused by the multiyear 1998/99/00 La Nina, similarly to the 1973/74/75/76 La Nina.

And as discussed above, La Nina events have been established by Trenberth et al as the periods of OHC recharge. The decadal and multidecadal declines in tropical Pacific OHC with the short-term recharges do not appear to be consistent with what should be expected if the constantly increasing infrared radiation from greenhouse gases had a measureable effect on OHC.

END OF UPDATE

SOURCES

ERSST.v2 data was used for the post “Can El Nino Events Explain All of the Global Warming Since 1976?” Parts 1 and 2 and the supplements. NOAA NOMADS was the source:
http://nomads.ncdc.noaa.gov/#climatencdc

As of this writing, NOAA is updating the ERSST.v2 data on NOMADS and long-term data is not available. However, the KNMI Climate Explorer website also has ERSST.v2 data. HADISST data could be used to verify the graphs, too; it makes little difference. The step changes are there regardless of the dataset.
http://climexp.knmi.nl/selectfield_obs.cgi?someone@somewhere

In my post “There Are Also El Nino-Induced Step Changes In The North Atlantic,” OI.v2 SST data was used primarily. It’s available through NOMADS here:
http://nomad3.ncep.noaa.gov/cgi-bin/pdisp_sst.sh?lite

The Sato Index Data is available from GISS at:
http://data.giss.nasa.gov/modelforce/strataer/
Specifically:
http://data.giss.nasa.gov/modelforce/strataer/tau_line.txt