Countdown to an "unprecedented warm decade" – 2 months to go

Global Temperatures This Decade Will Be The Warmest On Record…

…And It Will Be Exploited By Those Who Fail To Understand The Reasons For The Rise

Guest post by Bob Tisdale

snowman_forecaster

INITIAL NOTES

For some visitors to this blog, this post will be a merging and rehashing of a few of my earlier posts. But this post is different in a very important way. I have attempted to simplify the discussion of El Nino-caused step changes for those with less technical backgrounds.

The post does assume the reader knows of El Nino and La Nina events. If not, here are links to two NOAA El Nino Frequently Asked Question web pages:

http://www.aoml.noaa.gov/general/enso_faq/

http://faculty.washington.edu/kessler/occasionally-asked-questions.html

The following narrated video “Visualizing El Nino” from the NASA/Goddard Space Flight Center Scientific Visualization Studio provides an excellent overview of the 1997/98 E; Nino, one of the El Nino events that created the aftereffects illustrated in this post.

YouTube Link:

http://www.youtube.com/watch?v=DbNzw1CCKHo

I have provided links to the referenced studies and to the posts that provide more detailed explanations at the end of the following. They do not appear within the general discussion of this post.

Many of the illustrations in the following are .gif animations, with 5- to 10-second pauses between cells.

GLOBAL TEMPERATURES THIS DECADE WILL BE THE WARMEST ON RECORD

It became apparent a number of years ago that the current decade, the 2000s, would have the highest surface temperature since the start of the instrument temperature record. Prior to now, the record decade for Global Surface Temperature Anomalies, Global Lower Troposphere Temperature (TLT) Anomalies, and Global Sea Surface Temperature (SST) anomalies had been the 1990s. Table 1 shows the average 1990s and 2000s (to date) temperature anomalies furnished by different suppliers, and the difference between the two decades. And with the end of this decade drawing near, one should expect to hear of this new record time and time again. There are those who will exploit this in the next few months and in the years to come. Those parties will, of course, blame anthropogenic greenhouse gases for the rise.

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Table 1

THOSE WHO TRUMPET THE ELEVATED TEMPERATURES WILL FAIL TO ACKNOWLEDGE THE NON-LINEAR RELATIONSHIP BETWEEN THE EL NINO-SOUTHERN OSCILLATION (ENSO) AND GLOBAL TEMPERATURES

There have been a number of recent research papers that have illustrated a linear relationship between El Nino-Southern Oscillation (ENSO) and global temperature. These papers contradict what is clearly visible in the instrument temperature record, and that is, that the relationship between ENSO and global temperature is non-linear. In a comparison of global temperatures and natural variables, the researchers scale one of the ENSO indices, and after adjusting for other natural variables such as solar irradiance and volcanic aerosols, the researchers claim the difference between those natural variables and global temperatures must be caused by the increase in anthropogenic greenhouse gases. A simplified example of these comparisons is shown in Figure 1; it compares global SST anomalies and scaled NINO3.4 SST anomalies, one of the ENSO indices. It also shows their linear trends. I’ve excluded volcanic aerosol and solar adjustments to simplify the illustration. Note how the Global SST anomaly trend is increasing while the NINO3.4 SST anomaly trend is decreasing. As noted earlier, there are those who would like you to believe that the difference in those trends is caused by anthropogenic greenhouse gases.

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Figure 1

MULTIYEAR AFTEREFFECTS OF ENSO ARE VISIBLE AS STEP CHANGES IN THE SST RECORDS

The first dataset to be discussed is the sea surface temperature (SST) anomalies of the East Indian and West Pacific Oceans. This dataset represents approximately 25% of the global ocean surface area between 60S and 65N. A sizeable area, as can be seen in Figure 2.

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Figure 2

Figure 2 also shows the location of the NINO3.4 region of the equatorial Pacific. Its coordinates are 5S-5N, 170W-120W. Climate change researchers use this and other similar datasets when studying the magnitudes of El Nino and La Nina events and how often those events occur. Meteorologists also monitor NINO3.4 SST anomalies and other ENSO indexes to help them forecast the impacts of the current event on regional climate, hurricanes, etc. The SST anomalies of the NINO3.4 area of the Pacific correlate well with global temperature measurements. That is, when the SST anomalies of the NINO3.4 area rise during an El Nino event, global SST anomalies, and global TLT anomalies, and global surface temperature anomalies typically rise by lesser amounts. Researchers assume this relationship is constant, that it is linear, but as will be shown in the following, it is not linear. The global response to La Nina events is not the same as it is to El Nino events. This will be clearer as the discussion progresses.

Keep in mind that it is not only the SST anomalies of the NINO3.4 that rise and fall during El Nino and La Nina events. As can be seen in the video “Visualizing El Nino” above, the SST anomalies entire tropical Pacific are impacted.

Of the 9 official El Nino events since November 1981 (the start year of the SST dataset used to illustrate the effect), only two of these specific major traditional El Nino events occurred, one in 1986/87/88 and the other in 1997/98. See Figure 3, which is a .gif animation of the time-series graph of NINO3.4 SST anomalies. The other significant traditional El Nino in 1982/83 was counteracted by the volcanic eruption of El Chichon.

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Figure 3

Links to the individual cells of Figure 3:

Link to Figure 3 Cell A:

http://i33.tinypic.com/9pw0no.png

Link to Figure 3 Cell B:

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

Link to Figure 3 Cell C:

http://i35.tinypic.com/2yorexg.png

Something very curious happens in the East Indian and West Pacific area of the global oceans shown in Figure 2. The SST anomalies of the East Indian and West Pacific Oceans rise in steps in response to specific El Nino events. These particular El Nino events are major events that are traditional in nature, as opposed to El Nino Modoki (pseudo El Nino events), and they are also El Nino events that have not been impacted by explosive volcanic eruptions, such as El Chichon in 1982 and Mount Pinatubo in 1991.

Figure 4 is a .gif animation of two datasets presented in different ways. Cell A is a graph that compares the SST anomalies of the NINO3.4 region of the equatorial Pacific to the SST anomalies of the East Indian and West Pacific Oceans. The NINO3.4 SST anomalies have been scaled (multiplied by a factor of 0.2 in this case) so that the changes in them during the El Nino events of 1986/87/88 and 1997/98 are approximately the same magnitude as the responses in the East Indian and West Pacific Oceans. Note how the SST anomalies of the East Indian and West Pacific Oceans had little response to the 1982/83 El Nino. As discussed earlier, that El Nino was counteracted by the sunlight-blocking volcanic aerosols of the explosive eruption of El Chichon. Note also that there is a dip in the East Indian and West Pacific SST anomalies in 1991 and a rebound a few years later. That dip and rebound is caused by the eruption of Mount Pinatubo. In Cell B, linear trend lines have been added to the same datasets to show the relationship presented by researchers who assume the relationship between ENSO and global temperature is linear. The linear trends skew perspective and hide the actual cause of the rise in SST anomalies of the East Indian and West Pacific Oceans. In Cell C, I’ve included the average East Indian and West Pacific SST anomalies for the period before the 1986/76/88 El Nino, the period between the 1986/76/88 and 1997/98 El Nino events, and the period after the 1997/98 El Nino. These averages highlight the step changes that occurred in this portion of the global ocean. Again, these step changes are aftereffects of the 1986/87/88 and 1997/98 El Nino events.

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Figure 4

Links to the individual cells of Figure 4:

Link to Figure 4 Cell A:

http://i33.tinypic.com/2cparf4.png

Link to Figure 4 Cell B:

http://i38.tinypic.com/dz5go.png

Link to Figure 4 Cell C:

http://i33.tinypic.com/14wu8pk.png

As you will note, the multiyear aftereffects aren’t true step changes. The SST anomalies for the East Indian and West Pacific Oceans don’t remain at the new higher temperatures indefinitely. They do, however, remain at higher levels (failing to respond fully to the La Nina) until the next series of lesser El Nino events drive the temperatures back up again, helping to maintain the higher levels. (The effects are easier to describe as step changes, which is why I refer to them that way.)

It is important to notice that the response of the East Indian and West Pacific Oceans to 1998/99/00 La Nina was not the same as the response to the El Nino that came before it. The SST anomalies for this area of the global oceans rose as would be expected in response to the El Nino, but it did not respond fully to the La Nina phase. Global SST response to La Nina events is not always the same as it is to El Nino events. And this difference between how Global SST responds to El Nino and La Nina events causes Global SST to rise.

These step changes in the East Indian and West Pacific Ocean SST anomalies are important for a number of reasons. First, the oceans represent approximately 70% of the surface area of the globe, and SST anomalies are included in the calculation of global surface temperature by GISS, Hadley Centre, and NCDC. Refer again to Table 1. In fact, the NCDC’s Optimum Interpolation SST dataset (OI.V2) used in Figure 4 has been included by the Goddard Institute for Space Studies (GISS) in their GISTEMP product since 1982. Second, these step changes are not reproduced by climate models. They also are not acknowledged by the scientific community–if they were, the papers listed at the end of this post would not illustrate a linear relationship between ENSO and global temperature. I have searched but have been unable to find any scientific paper that discusses these step changes. Third, the step changes bias the global SST anomalies upward and give the impression of a gradual increase in SST anomalies. This can be seen in a comparison graph of the SST anomalies of the East Indian and West Pacific Oceans, the SST anomalies of the “Rest of the World” (East Pacific, Atlantic, and West Indian Oceans), and the combination of the two, Figure 5. The period since 1996 is unique in the last 40+ years. There haven’t been any major volcanic eruptions to add noise to the data. This is why the data in Figure 5 starts in 1996.

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Figure 5

Note how in Figure 5 the East Indian and West Pacific SST anomalies linger at the elevated levels while the SST anomalies for the “Rest of the World” are mimicking the variability of the NINO3.4 SST anomalies, shown in Figure 3. (That is, the SST anomalies for the “Rest of the World” are responding as researchers expect to both El Nino and La Nina events.) Over the next few years, ocean currents “mix” the elevated SST anomalies of the East Indian and West Pacific Oceans with the depressed SST anomalies of the “Rest of the World” oceans, dropping one and raising the other, until they intersect in 2003. This is more than 4 years after the end of the 1997/98 El Nino. Because the Global SST anomalies are a combination of the two, they are biased upward by the elevated East Indian-West Pacific SST anomalies and by the mixing with the waters of the “Rest of the World”. This gives the false impression of a gradual increase in global SST anomalies.

In other words, the effects of the major traditional El Nino events can linger for at least 4 years, causing gradual increases in global sea surface temperatures during that time. This gradual increase is incorrectly attributed to anthropogenic sources.

These effects are also discussed and illustrated in my video “The Lingering Effects of the 1997/98 El Nino”.

YouTube Link:

http://www.youtube.com/watch?v=4uv4Xc4D0Dk

MULTIYEAR AFTEREFFECTS OF ENSO ARE ALSO VISIBLE AS STEP CHANGES IN THE TLT RECORDS

Since 1979, two groups have analyzed the satellite-based Microwave Sounding Unit (MSU) radiometer data to determine atmospheric temperatures at different levels. These groups are Remote Sensing Systems (RSS) and the University of Alabama in Huntsville (UAH). We’ll be using the data from RSS in this discussion. One dataset, the Lower Troposphere Temperature (TLT) anomalies, correlate well with the global surface temperature anomalies determined from direct land and sea surface temperature observations.

Lower Troposphere Temperature (TLT) anomalies also show upward step changes in response to the significant traditional 1986/87/88 and 1997/98 El Nino events. And similar to the discussion of sea surface temperatures above, only a portion of the global TLT anomalies show clear signs of these upward steps. In this case, it’s the latitude band of 20N to 82.5N or the Mid-To-High Latitudes of the Northern Hemisphere. Refer to Figure 6 for the area of the globe included within these latitudes. It represents in the neighborhood of 33% of the global surface area.

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Figure 6

The graph in Figure 7 compares the NINO3.4 SST anomalies to the Lower Troposphere Temperature (TLT) anomalies of the Mid-To-High Latitudes of the Northern Hemisphere. The scaled NINO3.4 SST anomalies are used again as a reference for the timing and magnitude of significant traditional El Nino events. As you can see, the TLT anomaly data for this area of the globe is noisy, but it is obvious that the TLT anomalies rose since 1979, a rise that is normally attributed to manmade greenhouse gases.

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Figure 7

A common technique used to reduce data noise is to smooth it by calculating the average of a number of months before and after a given month, and to calculate this average for each month for the entire length of the dataset. (The same technique was used in Figure 5.) The TLT anomaly data in Figure 8 has been smoothed with a 13-month running average filter. Note how, when compare to Figure 7, there is much less noise in the smoothed data. Figure 8 is another .gif animation. It illustrates the TLT anomaly data for the Mid-To-High Latitudes of the Northern Hemisphere and the scaled NINO3.4 SST anomalies from different points of view. Cell A illustrates the data without any comments. Depending on your perspective, you can see a gradual rise in the TLT anomaly dataset that’s disrupted by ENSO events and volcanic eruptions or you can see three periods of relatively flat TLT anomalies that are punctuated by ENSO and volcanic eruptions with two major step increases caused by the 1986/87/88 and 1997/98 El Nino events. In Cell B, the impacts of the two major volcanic eruptions are noted. These are the 1982 eruption of EL Chichon and the Mount Pinatubo eruption in 1991. As with the SST data, the El Chichon eruption counteracted the impact of the 1982/83 El Nino. But the lesser El Nino in 1991/92 was no match for the Mount Pinatubo eruption, and TLT anomalies made a substantial drop. The TLT anomalies rebounded a few years later as the volcanic aerosols in the stratosphere dissipated. Cell C shows the positive linear trend of the TLT anomalies for the Mid-To-High Latitudes of the Northern Hemisphere and it shows the negative trend in the SST anomalies of the NINO3.4 region of the equatorial Pacific. The difference between the two, as discussed earlier, is attributed by researchers to anthropogenic greenhouse gases. However, the attribution is unfounded when the global data is broken down into smaller subsets. The heat released by significant El Nino events can and do cause step changes in the TLT anomalies of the Mid-To-High Latitudes of the Northern Hemisphere. This is clearly visible when the average temperatures before and after those significant El Nino events are displayed on the graph, Cell D.

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Figure 8

Links to the individual cells of Figure 8:

Link to Figure 8 Cell A:

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Link to Figure 8 Cell B:

http://i37.tinypic.com/2yjocr9.png

Link to Figure 8 Cell C:

http://i38.tinypic.com/2jcdc13.png

Link to Figure 8 Cell D:

http://i37.tinypic.com/2ue1jz8.png

It is primarily those two shifts in the Mid-To-High Latitude TLT Anomalies of the Northern Hemisphere that cause the upward trend in Global TLT Anomalies.

DO ANTHROPOGENIC GREENHOUSE GASES FUEL EL NINO EVENTS?

The source of heat for El Nino events is the Tropical Pacific, and there is no evidence that greenhouse gases have a significant effect on the Ocean Heat Content (OHC) anomalies of the Tropical Pacific. Refer to Figure 9. It is also a .gif animation. Cell A shows the comparison graph of Tropical Pacific OHC, scaled NINO3.4 SST anomalies, and scaled Sato Index of Stratospheric Aerosol Optical Thickness. The Sato Index data is presented to illustrate the timing of explosive volcanic eruptions. Like the other comparisons in this post, the NINO3.4 SST anomalies are used to illustrate the timing and magnitude of El Nino and La Nina events. The OHC dataset was created by the National Oceanographic Data Center (NODC). It presents OHC to depths of 700 meters. This OHC data was introduced with the Levitus et al (2009) paper “Global Ocean Heat Content 1955-2008 in light of recently revealed instrumentation problems”. Cell B highlights the two decade-long declines in Tropical Pacific OHC. Cell C calls attention to the upward surges (steps) in Tropical Pacific OHC that occurred during the multiyear La Nina events that followed the 1972/73 and 1997/98 El Nino events. And Cell D highlights a curious rise in Tropical Pacific OHC that occurred in the few years leading up to the 1997/98 El Nino. I have searched for but have not found any scientific paper that discusses this sudden surge that fueled the 1997/98 El Nino.

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Figure 9

Links to the individual cells of Figure 9:

Link to Figure 9 Cell A:

http://i33.tinypic.com/2gwys1t.png

Link to Figure 9 Cell B:

http://i37.tinypic.com/kamom.png

Link to Figure 9 Cell C:

http://i35.tinypic.com/w075g6.png

Link to Figure 9 Cell D:

http://i34.tinypic.com/10e28ic.png

An additional note about Figure 9: Note how the OHC dips during the El Nino events and rebounds during the La Nina events. The El Nino discharges heat from the Tropical Pacific, and the La Nina recharges the heat. This is accomplished by variations in total cloud amount. If the La Nina is not being impacted by volcanic aerosols and if the La Nina lasts for more than one year, ocean heat content rises above its previous level, creating the upward step.

The changes in Tropical Cloud Amount Percentage mimic NINO3.4 SST anomalies. Refer to Figure 10. That is, when NINO3.4 SST anomalies rise, Tropical Pacific Cloud Amount increases, and when NINO3.4 SST anomalies drop during the La Nina phase, Tropical Pacific Cloud Amount decreases. Less cloud cover means more downward shortwave radiation (visible sunlight) is able to warm the Tropical Pacific. In Cell C of Figure 10, the sudden drop in Tropical Pacific Cloud Amount in 1995 is highlighted. As noted above, it appears this decline in cloud amount fueled the 1997/98 El Nino.

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Figure 10

Links to the individual cells of Figure 10:

Link to Figure 10 Cell A:

http://i35.tinypic.com/4rxele.jpg

Link to Figure 10 Cell B:

http://i36.tinypic.com/2z4d6hc.jpg

Link to Figure 10 Cell C:

http://i36.tinypic.com/34obno7.jpg

NATURAL VARIATIONS IN THE NORTH ATLANTIC SST ALSO CONTRIBUTED TO THE DIFFERENCE IN GLOBAL TEMPERATURE BETWEEN THE 1990s AND THE 2000s

The SST anomalies of the North Atlantic Ocean are also impacted by another natural variable, the Atlantic Multidecadal Oscillation or AMO. The AMO is a semi-periodic variation (50 to 80 years) in the SST anomalies of the North Atlantic that has its basis in Thermohaline Circulation (THC) or Atlantic Meridional Overturning Circulation (AMOC). These variations are visible in the reconstruction of North Atlantic SST from 1567 to 1990, Figure 11. This dataset was created by Gray et al (2004) “Atlantic Multidecadal Oscillation (AMO) Index Reconstruction”. (IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2004-062. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.)

http://i36.tinypic.com/wld5kl.jpg

Figure 11

For the period of the instrument temperature record, the AMO is presented as detrended North Atlantic SST anomalies. Refer to Figure 12, which is also a .gif animation. Cell A of Figure 12 illustrates the AMO data calculated by the NOAA Earth System Research Laboratory (ESRL) from January 1956 to March 2009. The data has been smoothed with a 37-month filter to remove the noise. Cell B notes that the AMO is a naturally occurring variation in the SST anomalies of the North Atlantic. And Cell C illustrates the average AMO SST values for the 1990s and the 2000s. The difference between these two averages represents the contribution of the AMO to the rise in North Atlantic SST Anomalies from the 1990s to the 2000s. Keep in mind that, while the North Atlantic covers only a surface area that is approximately 15% of the global oceans, the AMO is also known to also impact the surface temperatures of Europe and North America and the SST of the Eastern Tropical Pacific.

http://i38.tinypic.com/oj4bqg.gif

Figure 12

Links to the individual cells of Figure 12:

Link to Figure 12 Cell A:

http://i37.tinypic.com/mwqeqh.jpg

Link to Figure 12 Cell B:

http://i34.tinypic.com/kaqtjq.jpg

Link to Figure 12 Cell C:

http://i35.tinypic.com/2gtddn7.jpg

CLOSING

There is little doubt that the decade of the 2000s will have higher land surface, sea surface, and lower troposphere temperature anomalies than the 1990s. There will be those who will wrongly attribute the rise from decade to decade to anthropogenic greenhouse gases, when it is very apparent that the actual cause is the lingering effects of the 1997/98 El Nino event. Attempts will be made to contradict the obvious by those who fail to acknowledge or comprehend the multiyear aftereffects of significant traditional El Nino events. They will present numerous unfounded arguments. Here are a few that have been tried.

Argument 1: The short-term global warming of El Nino events are countered by the short-term global cooling of the La Nina events that follow them.

What The Instrument Temperature Record Shows: That’s true for only parts of the globe and for some El Nino events. It is not true, however, for the SST anomalies of the East Indian and West Pacific Oceans and for the TLT anomalies of the Mid-To-High Latitudes of the Northern Hemisphere. Refer to Figures 4 and 8. The effects of the 1986/87/88 and the 1997/98 El Nino lingered through the La Nina events that followed them in those datasets. This created the appearance of gradual rises in global SST and TLT anomalies.

Argument 2: Global warming caused by anthropogenic greenhouse gases is responsible for the increase in the number of major El Nino events since 1975. (This argument is normally made by someone referring to an ENSO Index that starts in 1950.)

What The Instrument Temperature Record Shows: There are multidecadal variations in the frequency and magnitude of ENSO events. This can be seen by smoothing the NINO3.4 SST anomalies from 1870 to 2009 with a 121-month filter. Refer to Figure 13. During epochs when the frequency and magnitude of El Nino events outweigh the frequency and magnitude of La Nina events, global temperatures rise. And during epochs when the frequency and magnitude of La Nina events outweigh the frequency and magnitude of El Nino events, global temperatures drop.

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Figure 13

Argument 3: El Nino events don’t create heat.

What The Instrument Temperature Record Shows: During El Nino events, warm water that had been stored below the surface of the western tropical Pacific (in the Pacific Warm Pool) sloshes to the east and rises to the surface. Tropical Pacific SST anomalies increase in response. In this way, more heat than normal is released from the tropical Pacific to the atmosphere. But El Nino events not only release heat into the atmosphere, they also shift atmospheric circulation patterns (Hadley and Walker Circulation, surface winds, cloud cover). These shifts in the circulation patterns and cloud cover cause surface temperatures and OHC outside of the tropical Pacific to rise.

It is important to note that the vast majority of the warm water that sloshes east during the El Nino had been stored below the surface before the El Nino. While below the surface (to depths of 300 meters) it was not included in the instrument temperature record. But during the El Nino, that warm water has been relocated to the surface and is included in the surface temperature record. So, El Nino events relocate warm water from an area that was not included in the calculation of global temperature to the surface where it is included.

Argument 4: Climate models used by the IPCC reproduce these El Nino-induced step changes.

What The Climate Models Show: Most of the climate models (GCMs) used by the IPCC in AR4 for hindcasting 20th Century climate do not bother to model ENSO. Those that make the effort do not model it well. The frequency, magnitudes, linear trends, and multiyear aftereffects of those models do not match the surface temperature record. The step changes that exist in the instrument temperature record, which are the bases for the much of the rises in global temperatures, do not exist in the model outputs of the 20th century.

If and when GCMs can reproduce the past frequency and magnitude of ENSO events, if and when GCMs can reproduce the multiyear aftereffects of ENSO events, which are these El Nino-induced step changes (including the ones that also appear in the OHC records), then GCMs may have some predictive value. At present they cannot reproduce ENSO or its multiyear aftereffects. At present they have no value.

This failure of GCMs to properly account for the multiyear impacts of major El Nino events (and other natural variables such as the North Atlantic Oscillation) can be seen in a graph of the actual rise in global OHC versus the projected rise forecast by GISS, Figure 14. The GCM used by GISS based its projection on the rise in Ocean Heat Content during the 1990s, assuming the trend would continue at that pace. But during the 1990s, the vast majority of the rise in OHC was caused by the combined effects of ENSO and the North Atlantic Oscillation, and these are natural variables that the GISS GCM did not model. Since 2003, Global Ocean Heat Content has been relatively flat, while the GISS projection reaches to unrealized levels.

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Figure 14

LINKS TO MORE DETAILED DISCUSSIONS

The upward step changes in the SST anomalies of the East Indian and West Pacific Oceans were discussed in the following posts:

1.Can El Nino Events Explain All of the Global Warming Since 1976? – Part 1

2.Can El Nino Events Explain All of the Global Warming Since 1976? – Part 2

And I discussed the step changes in the Mid-To-High Latitudes of the Northern Hemisphere in the post RSS MSU TLT Time-Latitude Plots…Show Climate Responses That Cannot Be Easily Illustrated With Time-Series Graphs Alone.

The erroneous assumption that the relationship between ENSO and global temperatures is linear was discussed in the following posts:

1.Multiple Wrongs Don’t Make A Right, Especially When It Comes To Determining The Impacts Of ENSO

2.Regression Analyses Do Not Capture The Multiyear Aftereffects Of Significant El Nino Events

3.The Relationship Between ENSO And Global Surface Temperature Is Not Linear

This link discusses and illustrates that El Nino Events Are Not Getting Stronger.

The impacts of natural variables (ENSO and NAO) on Ocean Heat Content were discussed in the following posts:

1.ENSO Dominates NODC Ocean Heat Content (0-700 Meters) Data

2.North Atlantic Ocean Heat Content (0-700 Meters) Is Governed By Natural Variables

3.NODC Corrections to Ocean Heat Content (0-700m) Part 2

Refer also to La Nina Events Are Not The Opposite Of El Nino Events.

The curious drop in cloud amount in 1995 and its possible impact on the 1997/98 El Nino is discussed further in Did A Decrease In Total Cloud Amount Fuel The 1997/98 El Nino?

LINK TO LEVITUS ET AL (2009)

I referred to the Levitus et al (2009) paper “Global Ocean Heat Content 1955-2008 in light of recently revealed instrumentation problems”. Here’s a link to the paper:

ftp://ftp.nodc.noaa.gov/pub/data.nodc/woa/PUBLICATIONS/grlheat08.pdf

PAPERS THAT PORTRAY A LINEAR RELATIONSHIP BETWEEN ENSO AND GLOBAL TEMPERATURES

In a good portion of this post, I’ve illustrated that the relationship between ENSO and global temperatures is not linear. The following is a list of papers that portray a linear relationship even though the instrument temperature record indicates otherwise. There are likely more of them in existence, and there will likely be more of them in the future.

Lean and Rind (2008), How Natural and Anthropogenic Influences Alter Global and Regional Surface Temperatures: 1889 to 2006

http://pubs.giss.nasa.gov/docs/2008/2008_Lean_Rind.pdf

Lean and Rind (2009), How Will Earth’s Surface Temperature Change in Future Decades? http://pubs.giss.nasa.gov/docs/2009/2009_Lean_Rind.pdfSanter, 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

http://pubs.giss.nasa.gov/docs/2001/2001_Santer_etal.pdfThompson, 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

http://www.nature.com/nature/journal/v453/n7195/abs/nature06982.html

Thompson et al (2009), Identifying signatures of natural climate variability in time series of global-mean surface temperature: Methodology and Insights

http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F2009JCLI3089.1

Preprint Version:http://www.atmos.colostate.edu/ao/ThompsonPapers/TWJK_JClimate2009_revised.pdf

Trenberth, K.E., J.M.Caron, D.P.Stepaniak, and S.Worley, (2002), Evolution of El Nino-Southern Oscillation and global atmospheric surface temperatures

http://www.cgd.ucar.edu/cas/papers/2000JD000298.pdfWigley, T. M. L. (2000), ENSO, volcanoes, and record-breaking temperatures

http://www.agu.org/pubs/crossref/2000/2000GL012159.shtml

SOURCES

OI.v2 SST data is available through the NOAA NOMADS website:

http://nomad3.ncep.noaa.gov/cgi-bin/pdisp_sst.sh?lite=

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

The AMO data is available through the NOAA ESRL website:

http://www.cdc.noaa.gov/data/correlation/amon.us.long.data

The RSS TLT data is available here:http://www.remss.com/data/msu/monthly_time_series/RSS_Monthly_MSU_AMSU_Channel_TLT_Anomalies_Land_and_Ocean_v03_2.txt

HADISST data (Used in Figure 13) NODC OHC data and ISCCP Total Cloud Amount data is available through the KNMI Climate Explorer website:

http://climexp.knmi.nl/selectfield_obs.cgi?someone@somewhere

The data for the North Atlantic SST Reconstruction is available through the NCDC’s World Data Center for Paleoclimatology:

ftp://ftp.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/amo-gray2004.txt

For those who want to verify the outputs of the GCMs used by the IPCC, refer to the KNMI Climate Explorer webpage here:

http://climexp.knmi.nl/selectfield_co2.cgi?someone@somewhere

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Adam from Kansas

Read it on Bob Tisdale’s site, it was pretty much a gimme this would be warmest decade on record in the temp. record earlier in the year unless there was a big crash in temps.
If CO2 really trapped heat like the IPCC says, would we not have seen a virtually flat trend in the Nino 3.4 region SST’s?

rbateman

The hottest decade on record is manufactured, plain & simple. All they had to do was to keep closing down the rural sites and/or playing data modification games with the bulk of the sites. The anomaly generated would be positive, despite the overall global cooling that is experienced in real life.
Too many posters have noticed the anomaly reports that don’t make a bit of sense for the area in which they live.
It makes sense if you live in one of the areas they mangled the output for. I’ve seen it go down right in my neck of the woods, more than once.
Let’s call it what it is: The biggest fixed outcome game in town.

rbateman

Argument 3: El Nino events don’t create heat.
And La Nina’s don’t consume it, either.
If it gets out of the ocean, the ocean has lost heat.
You now have a colder ocean than when you started.
If it fails to get into the ocean, it can’t be there to get out.
Enter the input at surface level that makes it through the atmosphere.
Change the atmosphere and more gets in or does not get in.
This IPCC lazy Susan is broken.

Evan Jones

Saying this decade is “hottest on record” is like saying inflation under Reagan’s first term was higher than inflation under Carter: True, but irrelevant.
Yes, it has been getting cooler at a slower rate than it warmed last decade. But the important question is whether it has been cooling or warming.
As Reagan answered: If the Carter administration were a book, you’d have to read it from back to front to get a happy ending. Same deal for the last decade of climate.

rbateman (15:21:24) : You began you comment with, “The hottest decade on record is manufactured, plain & simple. All they had to do was to keep closing down the rural sites and/or playing data modification games with the bulk of the sites. The anomaly generated would be positive, despite the overall global cooling that is experienced in real life.”
Your comment has nothing to do with this post. This post illustrates the natural causes for the difference in temperature between the two decades and it uses the data, not a climate model based on manufactured forcings, to explain it.
Also, your argument does not ring true. The number of land surface stations have no effect on TLT and SST anomalies. And TLT and SST anomalies will also be warmer this decade than they were in the 1990s.

hunter

The amount of warming involved, like all things to do with AGW, is a sparrow’s burp of significance.
Never in the history of the world has so much worry and money been spent on such a trifling amount of change.

rbateman: You wrote, “And La Nina’s don’t consume it, either.
If it gets out of the ocean, the ocean has lost heat.
You now have a colder ocean than when you started.”
As explained in the post, tropical Pacific cloud cover decreases during the La Nina and recharges the OHC, so the OHC is approximately the same as before the El Nino. Refer to Figures 9 and 10.

andy

Are you also a stock market chartist by any chance Anthony ?

rbateman

And make sure that brutally cold interior Antarctica is left out of the summation. Wouldn’t want to upset that carefully crafted anomaly.
At each step of the way, the data is remanufactured to exacting specifications to correct for Nature.
Word on the street is that she dumped AGW for Old Man Johnny Winter’s son, Cool Hand Luke.

hunter (15:42:33) : You wrote, “The amount of warming involved, like all things to do with AGW, is a sparrow’s burp of significance.”
Speaking of sparrow’s burps, here’s some trivia for you. In Levitus et al 2005, the abstract includes, “During 1955–1998 world ocean heat content
(0–3000 m) increased 14.5 X 10^22 J corresponding to a
mean temperature increase of 0.037 deg C.”
That’s right. Thirty-seven one-thousandths of a degree C. No wonder they use 10^22 Joules. Sounds so much more significant.
Regards.

Adam from Kansas (15:17:43) : You asked, “If CO2 really trapped heat like the IPCC says, would we not have seen a virtually flat trend in the Nino 3.4 region SST’s?”
The models actually predict an increasing trend in NINO3.4 SST anomalies, but the observed trend since 1900 has been flat.

rbateman (15:21:24) :
The hottest decade on record is manufactured, plain & simple. All they had to do was to keep closing down the rural sites and/or playing data modification games with the bulk of the sites. The anomaly generated would be positive, despite the overall global cooling that is experienced in real life.

How do you explain the satellite record. Note that in Bob’s Table 1 (above) the temperature change (2000s – 1990s) is similar for all data providers.

Bill Illis

Great post Bob.
It is pretty clear that the ENSO has impacted the temperature trend and while the ENSO was driving the temperature trend upward (part of it anyway), the pro-AGW set was more than happy to take credit for it as part of global warming.
Its not like the ENSO is a recent discovery. It goes way back and was first mentionioned as El Nino in 1892. Its just the climate scientists forgot about until about 2007 when they had to explain the temperature drop caused by the 2007-08 La Nina (although Trenberth was certainly on the case).
Now we even have the great Phil Jones trying to adjust for it (the great adjuster that is). When the impact is accounted for, there is less “global warming” and more “natural warming and cooling”.

rbateman

Bob Tisdale (15:45:30) :
Oh, I got it. It’s a zero-sum game until something comes along external to the Earth to force the atmosphere into protracted admit/reject incoming.
Otherwise there would be no extended Warm and Cold periods beyond the ocean cycles. The oceans behave like an electrolytic capacitor in a sense.
That the anomalies managed to stabilize before and after the modern CO2 rise says that rising C02 is not capable of stopping the discharge to space.
Trace content CO2 induced greenhouse trapping doesn’t work.
It might be responsible for changing the timing of the oceanic charge/dischare, but it’s still going to be a zero-sum game.

Paul Benkovitz

Strange, I thought every scientist would know the present decade ends Dec 31st 2010. I wonder what else they got wrong?

Adam from Kansas

Colder water of both the Humboldt current and a spot by Central America currently at the doorstep of the ENSO region
http://weather.unisys.com/surface/sst_anom.html
With that in mind what happens afterward when you show SST changes in those areas to the negative side during an El Nino event in past situations like this?

Ron de Haan

Abrupt warming and cooling by Don Easterbrook.
http://www.iceagenow.com/Abrupt_warming_and_cooling-Easterbook.htm

Adam from Kansas (16:57:38): You wrote, “Colder water of both the Humboldt current and a spot by Central America currently at the doorstep of the ENSO region
http://weather.unisys.com/surface/sst_anom.html
Consider that there are subsurface anomalies in the range of 6 to 7 degrees C and that those anomalies are moving to the east and toward the surface:
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_update/wkxzteq.shtml
Could you rephrase the question that followed?

Michael D Smith

Not sure if Anthony is, but I’ve dabbled in technical analysis. AGW is currently rated a SELL.

Roger Knights

“Strange, I thought every scientist would know the present decade ends Dec 31st 2010.”
Noughty, noughty.

rbateman

Which is why they are sening a re-marketing team to Copenhagen. They’ve got a line of Edsels stuffing the channel.

Uhhh. Wazzat?!

Hal

Paul Benkovitz (16:25:20) :
Strange, I thought every scientist would know the present decade ends Dec 31st 2010. I wonder what else they got wrong?
Yeah, like the 2nd Millenium ended Dec 31, 2000.
Did you wear your 3rd Millenium welcome party hat that night?
Go with the populist flow.

Steve

“The El Nino discharges heat from the Tropical Pacific, and the La Nina recharges the heat. This is accomplished by variations in total cloud amount. If the La Nina is not being impacted by volcanic aerosols and if the La Nina lasts for more than one year, ocean heat content rises above its previous level, creating the upward step.”
Gold! Now I’m starting to understand things. I’ve had a gut feeling for a while now that changes in ocean/sea cloud cover are driving climate change. GCRs… maybe. But for your theory, all the data is already there.
Proving that the energy transfer is ocean to atmosphere, and not the other way around, will kill CO2 centric theories. This is another nail.
What I find hilarious is the “mystery” behind why the antarctic sea ice has reacted to the warming so differently from the arctic. If you assume it’s because variations in cloud cover heated the oceans/seas, and that this heat takes 5 – 10 years to work it’s way out, the mystery doesn’t require pointing to an ozone hole and anomalous wind patterns (aka “BS”). The arctic has current flowing under it that originates in the tropics. Arctic sea ice can readily be melted from the bottom up years after a drop in cloud cover at the tropics. But the antarctic is shielded by a circumpolar current that has little mixing with the rest of the ocean… except right across from the tip of South America. And where is the antarctic having it’s “unprecedented” heating – right where a heated ocean model would predict.
The top 10 feet of the world’s oceans hold the same heat capacity as the entire atmosphere, after all. Change the albedo over that, and you shift the earth’s energy budget.

Adam from Kansas

Bob Tisdale: I usually use the TAO site by NOAA, they update the subsurface anomalies on that site daily.
http://www.pmel.noaa.gov/tao/jsdisplay/plots/gif/Dep_Sec_EQ_5d.gif
The trade winds have gotton stronger at the moment and easterlies extend almost to the west edge of the map, can you guess what might happen?
http://www.pmel.noaa.gov/cgi-tao/cover.cgi?P1=lat_lon_20091107_sst_hf_2009111017.gif&P2=xy12846_2009111017.plt001&P3=900&P4=456&P5=/cache-tao/st1/jsdisplay&script=jsdisplay/scripts/biggif.csh

TH

All the analysis and graphs in the world will not change the fact that the past decade was warm. You should never start a study from an entrenched viewpoint.

Paul Benkovitz (16:25:20) : “Strange, I thought every scientist would know the present decade ends Dec 31st 2010. I wonder what else they got wrong?”
It depends on whether you’re following ordinal or cardinal year names. There will be alarmist bloggers who, in the next few months, will jump all over the decade of 2000 to 2009 being warmer than 1990 to 1999. In fact, I’ve already seen evidence of it. If you’ll be happier with the ordinal year names, the only thing it changes is Table 1:
http://i36.tinypic.com/2qd20sx.png
Regards

John Phillips

Argument 3: El Nino events don’t create heat
The rebuttal of this argument makes no mention of the correlation between low % pacific tropical cloud cover prior to an En Nino. The point is made earlier in your excellent paper. Do the lack of clouds not create heat? Just suggesting the point could be re-made under argument 3.

carrot eater

Bob: Let me make sure I understand your thesis. You’re saying that global warming is essentially caused by a series of El Ninos: the redistribution of ocean heat in an El Nino brings about lasting changes in the earth’s radiative budget via some effect on clouds, and these changes persist over time and even through the La Ninas, so each El Nino event is like a ratchet.
Is this a fair paraphrase of your basic idea?

Paul Benkovitz (16:25:20) Sorry, forgot to change the title of Table 1:
http://i36.tinypic.com/oqxb41.jpg

Hank Hancock

Bob,
Thank you for such a well articulated explanation of El Nino and its relationships to climate. Until this article, I understood there was a relationship but was fuzzy on the mechanics. Now it all makes much better sense.
It now occurred to me that the climate system presents multistable characteristics – a normal response of a non-linear systems near equilibrium to small cyclical changes in input. It stands therefore that if we see stepped changes on a large scale and frequency (such as glacial and interglacial periods) we should also see it on an intermediate scale and frequency (SST steps). Your work seems to provide a good explanation of the mechanics behind the steps and underscores the fact that the steps are a product of non-linear behavior.
What doesn’t make sense is why some climatologists would reason a linear relationship between El Nino and global climate when the climate system is inherently non-linear by nature.

Richard

John Finn (16:07:26) :
rbateman (15:21:24) :
“The hottest decade on record is manufactured, plain & simple. All they had to do was to keep closing down the rural sites and/or playing data modification games with the bulk of the sites. The anomaly generated would be positive, despite the overall global cooling that is experienced in real life.”
How do you explain the satellite record…

The vast majority of the readers here believe from the evidence that this decade is probably the warmest in the measured temperature records. However rbateman is correct if you consider the manipulation / manufacturing of the paleontology records. So they also understand that this is no big deal.

carrot eater (18:26:13): You wrote, “You’re saying that global warming is essentially caused by a series of El Ninos: the redistribution of ocean heat in an El Nino brings about lasting changes in the earth’s radiative budget via some effect on clouds, and these changes persist over time and even through the La Ninas, so each El Nino event is like a ratchet.” You then asked, “Is this a fair paraphrase of your basic idea?”
Close but not quite. The instrument temperature record shows that since the late 1970s/early 1980s two significant El Nino events caused upward step changes in the SST and TLT anomalies of large portions of the globe, while the rest of the globe basically mimicked variations in NINO3.4 SST anomalies.

TH (18:18:04) : You wrote, “All the analysis and graphs in the world will not change the fact that the past decade was warm. You should never start a study from an entrenched viewpoint.”
I presented the fact that the period of 2000 to 2009 would be warmer than the ten-year period before it, then explained the reason for the rise in temperature.
I stated fact and used the instument temperature record to explain it.

carrot eater

Bob: That clarification (18:57:10) speaks to regional patterns. Leave aside the regional distribution for the moment; I’d like to get your take on the impact of El Nino on the global mean anomaly. That is the headline number, after all. Just point me to a specific spot above, if you covered it in the text.

Mark Wagner

Warmest decade on record. Of this there is no doubt.
It should not be a surprise that the warm years are clustered about the peak. This is why it’s called a “peak.”
The only issue is whether one is continuing to go higher, or already on the way back down.

Paul Vaughan

“Those parties will, of course, blame anthropogenic greenhouse gases for the rise”
If they do that, their credibility is shot.

Paul Benkovitz

Paul Benkovitz (16:25:20) :
Strange, I thought every scientist would know the present decade ends Dec 31st 2010. I wonder what else they got wrong?
Hal (17:34:16) :
Yeah, like the 2nd Millenium ended Dec 31, 2000.
Did you wear your 3rd Millenium welcome party hat that night?
Go with the populist flow.
Which one? believing a year zero exists or believing CO^2 is causing global warming?
Just because everyone says it doesn’t make it true.

Michael hauber

So everytime we have a significant el nino the world gets a little bit warmer? How many significant el ninos would it take before the world gets another 10 degrees warmer and we are all fried? How long have significant El Nino’s have we had in the past? How come we haven’t fried yet?
Under normal conditions a large El Nino puts a lot of heat into the system, and the intervening neutral and La Nina events will allow this heat to gradually escape, resulting in no overall trend in temperature.
Add a gradually increasing heat content due to Co2, and the jump in heat content during the El Nino is essentially the same. However the slow steady addition of heat due to Co2 during the rest of the cycle cancels out the loss of heat which sould be bringing the system back to equilibrium.
It will be interesting to see if the current El Nino results in another significant step up in temperature, or whether the appearance of a step up is simply a statistical fluke.

Tim

Bob – nice work. I need to read it all more closely, but it was a pattern I noticed as well in looking at the satellite temperature record.
I noticed a nearly flat temperature “trend” from 1979 – 1997 and again, a nearly flat “trend” from 1998 and beyond. When running the trend lines against those periods, the “step” became quite obvious and the CO2 explanation became pretty hard to digest, since I would have expected a more consistent rise, more or less year after year, had CO2 been the cause.
One question remains for me, however… What is driving the apparent heat build-up and release of the El Nino cycle? All that heat has to come from somewhere. (sorry if this was answered in the text, I’m still perusing it).

LarryOldtimer

Nice to hear, but I nevertheless won’t be giving away my winter clothing and other winter gear.
Let’s see, what’s next? Eviscerating chicken entrails to predict the future? Any oracles handy?
What most people would see, were it possible to see the future in a crystal ball would be . . . themselves peering into a crystal ball.

Norm in Calgary

AMSR-E Ice graph shows 2009-10 recovery as the least recovery since 2000! And what’s up with the two jump glitches in the chart, one in October and another one in November?

Interesting that reconstructed Atlantic SST were as warm as today during the Maunder minimum. Bob, the PDO is then just an aftereffect of series of prevailing El Nino/LaNina events? Is the cloud cover the governing mechanism, how to get upward steps or downward steps?
There are very pronounced SST steps in fifties-seventies either:
http://www.woodfortrees.org/plot/hadsst2gl/from:1940/to:1970

carrot eater: You wrote, “That clarification (18:57:10) speaks to regional patterns. Leave aside the regional distribution for the moment; I’d like to get your take on the impact of El Nino on the global mean anomaly.”
For the TLT anomalies, the ratchet explanation works very well for the mid-to-high latitudes of the Northern Hemisphere in response to specific El Nino events.
The global TLT anomalies appear to be the sum of three TLT latitude bands. The tropics follow NINO3.4 SST anomalies closely. The mid-to-high latitudes of the Northern Hemisphere have the obvious step changes in response to specific El Nino events (major traditional El Ninos that are not influenced by volcanic aerosols). The mid-to-high latitudes of the Southern Hemisphere have very subtle step changes in response to the same El Nino events. The marked-up Hovmollers…
http://i44.tinypic.com/16leq39.jpg
http://i41.tinypic.com/2vwzmdj.jpg
… from this post may help with the illustration:
http://bobtisdale.blogspot.com/2009/06/rss-msu-tlt-time-latitude-plots.html
For the SST anomalies, refer to the discussion of Figure 5. Does that answer your question?
Regards

dodgy geezer

When you say this was the warmest decade since the start of the instrument record, how long are we talking about here?
If the instrument temperature records go back to 1979, then the current decade is the warmest of three. Not amazingly unusual – there was a 33% random possibility anyway. One might equally say that the 1980s were ‘unprecedently cool’….

Barry Foster

VERY minor point about a comprehensive and compelling article: it’s Hadley Centre, not Hadley Center. It annoys a lot of us English. You wouldn’t say ‘A Midsummer Nite’s Dream’. Thank you.
Reply: A Midsummre Nite’s Dream? ~ ctm

Barry Foster (01:31:53) : You wrote, “VERY minor point about a comprehensive and compelling article: it’s Hadley Centre, not Hadley Center.”
Sorry, I missed it in Table 1. I’ll correct it on the version at my website.

dodgy geezer (01:13:46) : You asked, “When you say this was the warmest decade since the start of the instrument record, how long are we talking about here?”
Since the 1850s typically, at least that’s what I’m referring to.

Michael hauber: You wrote, “Under normal conditions a large El Nino puts a lot of heat into the system, and the intervening neutral and La Nina events will allow this heat to gradually escape, resulting in no overall trend in temperature.”
If there was sufficient time between El Nino events for the released heat to dissipate, this explanation would hold true for large traditional El Nino events, but the secondary lesser El Nino events that follow a major El Nino bump the temperatures back up. Therefore, your closing clause, “resulting in no overall trend in temperature,” is contradicted by the instrument temperature record of the TLT anomalies of the mid-to-high latitudes of the Northern Hemisphere and the SST anomalies of the East Indian and West Pacific Oceans.
You wrote, “It will be interesting to see if the current El Nino results in another significant step up in temperature, or whether the appearance of a step up is simply a statistical fluke.”
Since the late 1970s/early 1980s, the steps (plural) happened twice under the same circumstances, for the same type of El Nino event (major traditional El Ninos that were not impacted by volcanic eruptions). And yes, it will be interesting to see if the steps (TLT and SST) repeat. If there are no steps, the linear trend in global temperature (with ENSO removed) since 1999 would remain flat (refer to Knight et al 2009)…
http://www.metoffice.gov.uk/corporate/pressoffice/2009/global_temperatures_09.pdf
If the steps occur, the trend would increase, but I was saving that post until the 2009/10 El Nino peaks.
Let’s hope there are no major volcanic eruptions adding noise to the aftereffects.

juraj v.: You asked, “Bob, the PDO is then just an aftereffect of series of prevailing El Nino/LaNina events?
Refer to these posts for information on the PDO:
http://bobtisdale.blogspot.com/2009/04/misunderstandings-about-pdo-revised.html
http://bobtisdale.blogspot.com/2009/05/revisiting-misunderstandings-about-pdo.html
You asked, “Is the cloud cover the governing mechanism, how to get upward steps or downward steps?”
Other than volcanic eruptions, I haven’t seen evidence of downward steps.
For OHC anomalies, cloud cover changes during the multiyear La Nina events (that are not impacted by volcanic aerosols from major eruptions) cause the upward steps. For TLT anomalies, it’s the heat released by the major traditional El Ninos (that are not impacted by volcanic aerosols from major eruptions) that cause the upward steps. But for SST anomalies in the East Indian and West Pacific Oceans, the explanation is more complex. Refer to:
http://bobtisdale.blogspot.com/2009/01/can-el-nino-events-explain-all-of.html
You wrote, “There are very pronounced SST steps in fifties-seventies either:
http://www.woodfortrees.org/plot/hadsst2gl/from:1940/to:1970”
Some of those shifts in the HADSST2 data are responses to El Nino and La Nina events. Others are responses to volcanic eruptions. But the drop in 1945/46 is thought to be caused by a change in sampling (British versus U.S. ships and methods). This was discussed in Thompson et al (2008):
http://www.nature.com/nature/journal/v453/n7195/abs/nature06982.html
I’ve read the Hadley Centre is presently working at making corrections to their HADSST2 data and that those changes will be released this year. I don’t know how their corrections will change those shifts. That is, I don’t know whether they will also change one of the upward rebounds too. We’ll find out soon.