Of course, he didn't admit to that.
The spot of hot water "Bob" got into (archived here) is near the Philippines. He wrote about "The region east of the Philippines" and said:
For months, I’ve wanted to plot the data for that region, so that I could get a rough idea of its contribution to the global rate of sea level rise.
And he's done the sums, he says:
...the contribution of the region east of the Philippines to the global sea level rise isn’t a lot. It looks bad on the map, but due to its small size (only about 1.4% of the surface of the sea-ice-free global oceans) it doesn’t add much to the global rate of sea level rise, less than 5%.
Apparently he went and got lots and lots of data. He reckons he went and:
...divided the region bordered by the coordinates of 5N-15N, 125E-165E into sixteen 5-deg latitude by 5-deg longitude grids. Using the CU sea level wizard, I downloaded the time-series data for the center of each of those 5×5 grids. I then averaged the data for the 2 separate latitude bands (5N-10N and 10N-15N), and then took a weighted average of the sea level data for those 2 latitude bands to account for the very slight differences in area.
To what end? you ask. Well, he says that: "There is a very strong ENSO component to the sea level data for the region of unusual sea level rise, east of the Philippines."
He'd be right about that, but he didn't need to do all his sums to figure that out. One of the ENSO experts, Kevin Trenberth has written about this lots of times. For example, last January Kevin Trenberth pointed out that:
...the negative PDO might itself be setting the stage for a major compensation. The trade winds are a key player here, as changes in atmospheric pressure create the "sloshing water in a bathtub" effect that is a hallmark of both ENSO and the PDO. In the tropical Pacific, the tendency toward stronger-than-normal trade winds since the PDO’s last shift has pushed increasing volumes of water from east to west. Sea levels in and near the Philippines have risen by more than eight inches relative to the eastern tropical Pacific, which only added to the storm surge inflicted by Supertyphoon Haiyan in November 2013.
What "Bob Tisdale" was puzzling over was whether that wind-driven sea level rise in the western tropical Pacific is somehow contributing to the global mean sea level. If it is, it's not contributing much. And I'm not sure that it is. The water is being moved around. Oh, maybe there'll be a little bit of thermal expansion because the water is warm. But it's always warm there AFAIK. And there are cold anomalies elsewhere. In any case, the global mean sea level is calculated based on the volume of water in all the oceans. When one part of the sea rises, another part will fall to compensate, all the while the whole sea is rising. From the University of Colorado:
The term "global mean sea level" in the context of our research is defined as the area-weighted mean of all of the sea surface height anomalies measured by the altimeter in a single, 10-day satellite track repeat cycle. It can also be thought of as the "eustatic sea level." The eustatic sea level is not a physical sea level (since the sea levels relative to local land surfaces vary depending on land motion and other factors), but it represents the level if all of the water in the oceans were contained in a single basin. Changes to this eustatic level are caused by changes in total ocean water mass (e.g., ice sheet runoff), changes in the size of the ocean basin (e.g., GIA), or density changes of the water (e.g., thermal expansion).
The fact is that the higher level of water in the western tropical Pacific is to a great extent compensated by the lower level of water in the eastern tropical Pacific. That's where the wind blew it from. As Kevin Trenberth said:
“Eventually this difference in sea level becomes unsustainable, and the water sloshes back,” asserts Trenberth. “At some point, perhaps because of a fairly random weather event, we will likely have an El Niño event that leads us back into a positive PDO.”
Here's a map of the current sea level trends (not anomalies), so you can see that while the annual trend is rising near the Philippines, it's falling in parts of the eastern Pacific and elsewhere.
|Source: U Colorado|
There's also an outlook map on a BoM website, showing the higher sea level anomaly in the west and large expanses in the eastern Pacific where the anomaly is negative. (See below for the projections.)
ENSO can affect global sea level, not just the sea level in the tropical Pacific. Remember when there was that amazing La Nina that lifted up loads of water from the ocean and dumped on Australia and South America?
|Data source: U Colorado|
Anyway, back to "Bob" and his ENSO musings. He goes way further than most people would and computes how much the sea level rise near the Philippines contributed to the global sea level rise. What he didn't do was compute any corresponding fall elsewhere so I'm not really clear on what he thinks he was computing. He goes on to write:
Will the sea levels in that region continue at that pace into the future? Much of it depends on ENSO, and that’s something climate models still can’t simulate. Extending that excessive trend into the future would be foolish, especially when we have no understanding of what ENSO will do in the decades to come.
For the life of me I don't know why he suggests anyone would think that the sea level in that region would continue to rise at the same higher than average rate forever and a day. You'd end up with the sea shooting up through the sky eventually. Who does he think would be so foolish, one wonders. At least he has the sense to acknowledge that the rise in that particular area is to some extent tied up with ENSO, though he doesn't mention the Pacific Decadal Oscillation for some reason. I think he restricts himself to explaining the entire world and everything in it in terms of sea surface temperatures and ENSO. I can imagine him wondering if it's going to rain, then rushing in to check his latest SST charts and ENSO diagrams to see if he should carry a brolly. A bit like reading tea leaves.
Here's an excerpt from article about a study from July this year about sea level rise in the region and the Pacific Decadal Oscillation. Only some of the rise is from the PDO, the rest is from human-caused warming. Goodness, can that be right? A rise of one centimetre a year from human-caused warming? That's a lot! I can't get to the paper to see if that's what the paper found or if the press release messed it up a bit. Whatever - that part of the ocean is rising a lot. We do know that much. Kevin Trenberth mentioned a difference of eight inches (20cm) between the west and east tropical Pacific. Anyway, this is what the article says. (My emphasis.)
The research team estimated that areas of the ocean near the Philippines and northeast Australia are being raised by about 1 centimeter per year due to anthropogenic warming, which can increase the intensity of severe weather. “When water starts piling up there and typhoon-like storms are traveling over higher sea levels, it can be a bad situation,” said Hamlington.
Although global sea level patterns are not geographically uniform -- sea level rise in some areas correlate with sea level fall in other areas -- the average current global sea level rise is roughly 3 millimeters per year. Some scientists are estimating global seas may rise by a meter or more by the end of the century as a result of greenhouse warming.
“When the current PDO switches from its warm phase to its cool phase sea levels on the western coast of North America likely will rise,” said Leben of CU-Boulder’s aerospace engineering sciences department. “I think the PDO has been suppressing sea level there for the past 20 or 30 years.”
Here's the paper in Nature Climate Change. The press release talks about the PDO switching from the warm phase to the cool phase. The PDO index been negative for a few years and has shifted to positive this year. Whether that means a shift of the PDO regime overall or whether it's just an El Nino related shift that won't last, we'll find out sooner or later.
I'm told by an authority on the subject that sea level has dropped in the far western Pacific and has risen across much of the Pacific east of the dateline by a few inches. This experimental sea level outlook chart from BoM suggests that trend may continue. I've marked the dates on the two animations - one for the next two months and one for May - July next year. Click to enlarge as always.
|Source: BoM - Note: Experimental Only|
From the WUWT comments
There aren't many comments. Some people think that sea level should be fairly much the same everywhere. For example, Louis Hooffstetter writes:
November 23, 2014 at 6:29 amR. Shearer plays the innocent and asks:
I agree with Latitude. A localized rise in sea level is anomalous. My guess is that it correlates with a gravity anomaly, a temperature anomaly, or is simply due to error in in the data.
Why is the estimated formal error (Figure 5) is so high in certain regions? WUWT?
November 23, 2014 at 8:36 am
How does CO2 change gravity, by what mechanism?
Hamlington, B. D., M. W. Strassburg, R. R. Leben, W. Han, R. S. Nerem, and K. Y. Kim. "Uncovering an anthropogenic sea-level rise signal in the Pacific Ocean." Nature Climate Change (2014). doi:10.1038/nclimate2307