Vanuatu - something unusual and somehow encouraging

I'm busy updating spreadsheets for Pacific islands, mainly those in the Pacific Sea Level Project of the Australian National Tidal Unit - the straight-up and factual branch of the BOM. I updated Vanuatu last of all, as I'm working in alphabetical order. Here's the chart for the full record from 1993 to last month (November 2016):

The level has dropped to almost exactly what it was in 1993, from a peak in 2008-9. It seems to be a combination of SOI dropping from its high in 2009-10, a drop in sea temperature from 2008, and a rise in barometric pressure after 2011. A change of 1 hPa (=millibar) results in a change of 1cm in sea-level. Higher pressure, lower sea-level, and vice-versa. "Storm-surge" is due to low pressure (and high onshore winds) in a storm system. This is SOI to November 2016:

I'm checking on nearby (well, relatively) stations to see if there's anything remotely similar. I've already checked CGPS station data; here's that for Port Vila; the tide gauge is about 1 km away at the Cruise-ship port.

Source: SONEL

Although the red velocity analysis on the left says "Not robust", there's little change. More later maybe.

The 2015 El Niño and some super-hype from a couple of niños in the Grauniad

I've taken an unannounced break from blogging; the reasons I won't bore you with. I've decided to restart with a post about the current El Niño. First an update of the Southern Oscillation Index (SOI).

SOI 1990 - Aug 2015 (Source data BOM)        Click to enlarge

As you can see, the index has dropped from a high in 2010/11 into a strong El Niño (data to Aug 2015). However, there's some doubt as to the likely duration and strength. A couple of people are quite certain, however, as in this Guardian article. Please read it - it's either going to make you laugh (as I did) or cry, or both.

El Niño: a global weather event that may save California — and destroy the tropics 

The last time a really large El Niño occurred was during the Northern Hemisphere’s winter of 1997-98. Droughts, floods and outbreaks of infectious diseases plagued villages across Africa. Floods inundated Peru. Megafires rampaged through Indonesia. Fisheries collapsed off the coast of South America. Crops failed across much of the tropics and global food prices rose. Civil conflicts broke out in Africa and Asia.

Today, in all likelihood, we stand about a month away from another major El Niño. Current state-of-the-art forecasts tell us that an event similar to 1997-98 is likely to return this winter. Our own research on the human toll of El Niño suggests that households in the tropics will begin to feel the heat as early as September.

Do those linked forecasts tell us "that an event similar to 1997-98 is likely to return this winter"? No they don't - they don't mention 1997-98 anywhere, because they're forecasts, which are predicting a strong El Niño. The authors are hyping it up - to forecast doom and gloom, death and destruction, floods, drought and pestilence (I added in the pestilence myself - what's sauce for the goose....), and "the destruction of the tropics" apparently. Last time I heard, the tropics were still there after the 1997-8 El Niño, though a little frayed round the edges in one or two places.

Who are the authors of this apocalyptic treatise? They are Kyle Meng, who is "assistant professor in the Bren School of Environmental Science and Management and in the Department of Economics at the University of California, Santa Barbara.", and Solomon Hsiang is "associate professor of public policy at the University of California, Berkeley and a faculty research fellow at the National Bureau of Economic Research. He coauthored Economic Risks of Climate Change (just published) the analysis behind the Risky Business report by Michael Bloomberg, Hank Paulson & Thomas Steyer.".

Not climate scientists, nor meteorologists, but economists. Economists who actually understand less about El Niño and its effects and consequences than I do. Not only that, they manage to contradict themselves in their lurid and doom-laden article. Read it and spot the contradictions for yourself. An El Niño creates weather and climate disparities in the Pacific both east-west and north-south, and not just in the tropics, as these two economists-with-an-agenda would have us believe. Their linked forecasts (do they want us to actually read them? I did, most won't) make those disparities in temperature and precipitation quite clear.

Try this quote for a schoolboy howler "The fundamental physics of El Niño and its unequal effects have been around as long as civilization.". Really? and I, in my ignorance thought that the causes and effects were only recognised in the late 20th. century, and only begun to be fully understood as a result of the intensive recording and study of the 1997-8 event. You really are a couple of niños (Spanish for kids, children) aren't you? Stick to economics, guys, you may even be able to make a living out of it.

Poster-child Update - Kiribati & Tuvalu

Australia's National Tidal centre (BOM) finally got its act together and released data for December 2012 and January 2013 yesterday, for all South Pacific stations they maintain, and for ABSLMP stations in Australia. I'll be updating my reference pages on South Pacific and Australia (sidebar, top right) soon. In the meantime, I thought those who're interested might like to see the updated plots for the "poster children" of the CAGW fraternity - Kiribati (glug-glug!) and Tuvalu (gurgle!) both seemingly destined to disappear beneath the waves of an uncaring Pacific Ocean, like a latter-day Atlantis.

I avoid posting charts for either which end part way through the current year. Monthly averages vary widely over a year, and just a single unusually high (or low) month can change calculated trends quite dramatically. First Kiribati (pronounced Kiribass)

...... and Tuvalu

Despite the alarming-looking linear trends, in both cases "pulled down" on the left by the effect of the 1997/8 El Niño there's a great deal of "not much happening" here. The 37-month centred moving average (3-year) lines give a good indication of trend. SITREP - "nothing much going on, over and out".

"West Coast Sea Level Dropping" - oceanographer tells it like it is

Spartan Daily, the college newspaper of San Jose State University (California), has a report on a talk given by Larry Breaker, adjunct professor of physical oceanography at Moss Landing Marine Laboratories to students there,

New studies show regional sea levels are dropping on the West Coast even though global sea level rise is accelerating.

“Regional sea level rise is not uniform around the world,” said Larry Breaker, adjunct professor of physical oceanography at a talk at Moss Landing Marine Laboratories last week. “Although sea level is rising in some areas, in other areas it’s falling.”

Other studies (including mine, of course) have shown the same about US west coast sea-levels, though you'd not think so given the almost total silence on the issue in the media. Several of the students showed an alarming ignorance on the subject, given that they're studying at a marine laboratory.

“I was surprised to hear that,” said Moss Landing Marine Labs graduate student Christian Denney. “The concept that the local sea level was different from the global mean is new to me.” 

“(The sea level) has been steadily rising since the 1930s,” said Moss Landing Marine Labs graduate student Dorota Szuta. “But I didn’t realize that the sea level had actually been falling on the west coast of North America.”

And so it has, but the concept that the world climate and other metrics are anything but uniform shouldn't be news to anyone, especially students in a scientific discipline such as these two. I was going to say full marks to the prof. for telling it like it is, and so I do, but I shouldn't need to - isn't truth the universal standard in science?

More from the prof. -

“With GPS data we can now estimate local subsidence and uplift in the vicinity of many tide gauges,” he said. "Recently acquired GPS data near the San Francisco tide gauge suggests that it could be subsiding at rates approaching one millimeter per year."

Now that's interesting (at least to me) as I haven't been able to acquire any up-to-date GPS info for the US west coast. If you're interested, read the article for a few more interesting observations by the prof., and read his profile for even more interesting stuff - his experience in things oceanic is extensive. How refreshing to report on something in a positive light for a change, and not have to take a poke at anyone about what they've said or written (a few students excepted, of course).

The South-west "Cold Spot" - the other side of the coin

There was a lot in the press and on blogs back in June about the so-called "North-east Hot Spot" or NEH, an invention of the US Geological Survey. The authors of the USGS paper know what the weaknesses of their argument are, I'm sure - if they don't know, then they should have left their paper languishing in the "pending" tray. I'm planning another post on that subject soon, but there are two sides to every story, and there are two sides to every continent. If there's a "North-east hot spot", is there perhaps a "South-west cold spot"? There is indeed - and along a coast which is also subsiding slowly (which tends to raise sea level relative to the land), from San Diego in the south to just north of San Francisco, sea level hasn't risen in the last three decades. There are reasons for this of course, just as there are reasons behind the claimed "acceleration" in the north-east, but unlike the USGS authors, I'll not skate over or omit them. In my post on the continuing moderate sea-level rise around the Hawaiian Islands, I included this satellite graphic.

Map 1 - Linear trend (1993-2010) of satellite altimeter sea surface height showing he region of high rates in the western Tropical Pacific (Source)

I accept the data summarised therein, but it's a bad graphic - there's hardly any difference in the colours used for small negative, and small positive trends. Whether that's deliberate of not, I can't say, but the same criticism can't be levelled at this graphic representing a  slightly shorter period (to 2008). Its authors chose a switch from bright green to bright yellow either site of the scale zero, and I applaud them for it.

Map 2   Source: Why sea level rise isn’t level at all (NASA blog)

What stands out is the swathe of green (negative change) from Alaska down along the US west coast to Mexico and beyond. Incidentally, some sceptics (who should know better) have scoffed at graphics such as these, claiming that the very high rates of increase shown in the western Pacific are "fiction", and therefore the entire maps aren't to be trusted. I tended to agree (mea culpa) , until I began actually checking the depicted rates against tide gauge data over the time period(s) of the map(s). To date I've not found any but minor discrepancies, and where it's possible to take account of changes in land (and therefore gauge) height any such differences are mostly of the order of a few tenths of a mm/year at the very most.

However, looking at some of the actual plots will illustrate the situation and confirm the veracity of the satellite data. I initially planned to start in the south and work northwards, but decided to show what I think is the most interesting plot, for Port San Luis, N of Santa Barbara.

Note that while there is, overall, a small rate of rise (0.65 mm/year), the level since 1996 is lower than the 5-year-average peak in 1959. The level since 1980 is falling:

Port San Luis, CA                                                                          source: PSMSL

I'm not stating that sea level will continue to fall at Port San Luis. I'm not even suggesting it. I'm merely pointing out what is happening now (to the end of the last complete year of published data), and what has happened in recent decades.

My question at this point is whether city and state planners, local businesses and citizens actually know that sea level along the Californian coast has been stable for decades, and has been falling at almost all gauge sites for the last decade or two? If not, why not? Authorities around San Francisco Bay are wetting themselves about possible huge future sea level rise "predictions", and many appear to have convinced themselves that effects such as beach erosion are due to recent sea level rise, when the records show nothing of the sort. For example, there's been a gauge at Alameda Naval Air Station (East across the Bay from San Francisco) since 1939.

Alameda (Naval Air Station), CA                                                 source: PSMSL

... where the current 5-year average is lower than it was in the late 1960s, and the current rate is clearly negative. Most assessment reports I've seen brush the inconvenient facts "under the carpet" and only mention global data and the scary predictions. Some (see Missing the Point in California) are so mesmerised by this misinformation they can't see what's under their noses. There's no doubt that sea levels are rising globally. There's no doubt that effects such as ENSO raise and lower sea levels across the Pacific. The peaks from the strong 1982-3 and 1997-8 El Niños stand out for the two previous examples, and for all west-coast sites from southern California to Alaska. The Pacific Decadal Oscillation has an impact - it was strongly positive from the late 1970s to around 2008, and in that phase tends to raise sea levels in the west, and lower them in the east, our area of study.

Is the story the same at all stations in California? Not quite - Humboldt Bay (about 120 km S of the Oregon state line) is an outlier, and shows up on map 2 above (click to get the original) as a pale orange blob at the apex of the "bulge" of the Californian coast.

Source: PSMSL

Note however, that while the calculated trend is 4.7 mm/year overall, the rolling profile of the 3-year moving average is similar to the previous examples, and this indicates that North Spit must be sinking at a greater rate than other sites to the south, and a greater rate than the sea level is falling, resulting in a small positive rate since the early 1990s.

Plots for San Francisco and Point Reyes can be seen here, and data for all the west coast stations are linked on the Permanent Service for Mean Sea Level (PSMSL) page here - scroll down three-quarters of the page on the scroll bar.

Things will change, there's no doubt, but precisely which way, and to what extent, no one knows. Now that's a fact. Don't believe what you read, not even what you read here. I do my best to be truthful and unbiased, but I still have an overall point of view, and it may colour my presentation of what I see as facts. Check my references, check other blogger and web author's references, and remember - the truth may only be a click away (or two clicks if you have Windows Vista).

Extending the record - Nauru, west-central Pacific

Nauru is a small rocky island just 0.5° south of the equator. I have a slight connection with Nauru in that I was tasked with analysing rock samples from Nauru for phosphate content, many (many!) moons ago. Nauru has a SEAFRAME tide-gauge (and meteorological) installation on the west of the island, maintained by the South Pacific Sea Level and Climate Monitoring Program run by the Australian National Tidal Centre (BOM). A chart for Nauru (1993-2011) is included on the  South Pacific Sea Level reference page (sidebar top). PSMSL has data from an earlier gauge which I will refer to as Nauro-A, and the 1993 installation as Nauro-B. The overlap between the two records spans just 18 months, but the difference (due to different benchmarks used) varied little over that period, averaging 267mm.

With the data from Nauro-A reduced by 267mm until the date of the 1993 installation a reconstruction from mid-1974 to end 2011 is possible.

Note that while the overall rate is just 0.59 mm/year, the trend line is below the 13-month moving-average line on the left.

A plot of the annual rate from 1974 to the year on the lower axis confirms that the long-term rate has stabilised at just over 0.5 mm/year. Is Nauru rising from the waves, cancelling out the effect of much of the sea-surface rise?

The GPS plot from the station on Nauru seems to contradict that idea, at least between 2003 and 2009 (latest available on the 'net). If anything, the station dropped a little over that period, which would have increased the gauge readings. With this reconstruction, and the convincing data from Hawaii in my last post (amongst many other instances), I'm beginning to doubt the veracity of the claimed 3.2 mm/year "accelerated" rate post-1993 (satellite era for sea-level measurements).

Aloha! - Can the Hawaiian Islands tell us anything about global sea-level?

Sea-levels are rising relatively quickly in the western and south-western Pacific; they are rising hardly at all (falling in some locations) in the east, especially along the western seaboard of the U.S. This disparity is being driven by both sea temperature and wind direction (see ref. below), interrupted by an irregular "slosh" to the east during El Niño events, which significantly lowers sea-levels in the west, and raises them in the east (see The Footprint of El Niño).

Linear trend (1993-2010) of satellite altimeter sea surface height showing he region of high rates in the western Tropical Pacific (Source)

It occurred to me that somewhere in the "middle" of the Pacific, there should be a "mid-point" between the two extremes, and an ideal candidate seemed to be the Hawaiian Islands. The islands form a chain, running roughly west-north-west, formed as the supporting tectonic plate moved over a "hotspot" in the mantle, forming volcanoes which became islands when they broke the surface of the ocean. The oldest and most stable islands are to the NW, the youngest and volcanically active to the SE. The chain is far longer than most people think, extending to Midway Atoll (of WWII fame) far to the WNW of the well-known islands of the US state of Hawaii.

Source (much larger image): NOAA

Here's a simulated (and rather satisfying) satellite image of the main group; Kaua'i is the larger island on the left, O'ahu to the right of it, left of centre, Maui of similar size right of centre, and Hawa'ii (Big Island) very prominent on the right. I understand there's an undersea volcano some 20km to the SE of Big Island, it may have broken the surface in 20,000 years or so, and if mankind survives CAGW and catastrophic sea-level rise, might be seen by future generations. Could it be the white blob in the bottom RH corner? Book your holidays now.

Source: NOAA

Midway demonstrates the late 20th., early 21st. century shift upwards quite well (note that the data extends to end 2011 in all cases).

Midway shows an interesting trend; dropping until the late 1970s, climbing to a relatively stable period from the late 1980s to 1997, when there's a sharp dip (not reflected in the 5-year (61 month) moving average) due to the 1997/8 El Niño. There's then a sharp rise to 1999 and a significantly higher level (clearly shown by the moving average). Don't pay any attention to the overall trend; with such fluctuating levels, it's clearly meaningless. Moving down to the westernmost island in the main group. Kaua'i Island, where the overall trend is steadier and more meaningful:

No sign of late 20th. century acceleration evident there. Next O'ahu, where the capital Honolulu is situated:

Honolulu shows more peaky 5-year profile, but still a relatively steady trend, reflected in a plot of annual averages:

The long-term rate evolution below, produced by plotting the linear trend from 1905 to the year shown on the x-axis reveals that the long-term trend is still reducing; if there'd been a significant shift upwards in annual rate in recent decades, the plot would show first a flattening, then an upward trend, in this plot.

Mokuoloe Island (Coconut Island) in Kaneohe Bay on the NE coast of O'ahu.

Is the reason Honolulu and these other islands show a rate lower than what we're told the global rate was over the 20th.century due to the land rising? The GPS plot for Honolulu seems to show otherwise, at least for the recent past. There's little vertical movement; the trend is -0.3 mm/year since 1998.

Source: SONEL

Kahalui Harbor, Maui Island.

The rate's a little higher, but the overall profile is similar to Kaua'i Island.

Kawaihae, on the NW coast of Hawai'i Island (also known as Big Island, for obvious reasons)

This is the island with the BIG volcanoes, and the if change in actual sea level ( as opposed to the rate relative to the land, as shown by the tide gauge) is the same or nearly so as that at the islands covered so far, then it (or at least the gauge) must be sinking at a significant rate.

Hilo,on the NE of Hawai'i Island shows rather less of a rate. Perhaps the island is tilting somewhat?

I'd say that my hypothesis has some evidence to support it. If so, does it mean that some estimates of past and current sea-level rise are in error? There may be other gauges situated in "neutral zones" relatively unaffected by climatic cycles which give a better, or at least less distorted picture of sea-level rise than we're being presented with.

UPDATE: 14th. July 2012

I came across this picture of Hawai‘i Island, with the location of my "undersea volcano" actually known as Lōʻihi Seamount. It's not the "white blob in the bottom RH corner" of the illustration of the main island group above, but the lesser blob just above it, and it's 20 miles off the coast, not my "20 km".

 Lōʻihi Seamount,  Hawai'i Island, Hawai'i      Source: University of California, Santa Barbara

Amazingly enough, the article is titled Lö‘ihi: Hawai‘i’s Newest Island—But Don’t Book Your Flight Yet - the author obviously has a short-term outlook. If you're interested in volcanoes (who isn't?) read the article - it's fascinating.

Reference: Regional sea-level trends due to a Pacific trade wind intensification
Merrifield, M. A., and M. E. Maltrud, Geophys. Res. Lett., in press, 2011.

Data Sources: (in order of presentation):
Midway Island
Nawiliwili Bay, Kaua'i Island
Honolulu, O'ahu
Mokuoloe Island
Kahalui Harbor, Maui Island
Kawaihae, Hawai'i Island
Hilo, Hawai'i Island

Extending the record - Cook Islands, Rarotonga

There's been a lot of discussion over the past few years about the so-called "vanishing islands" in the central and western Pacific. Much of is nonsense, on the one hand alarmists claiming the populations are doomed, that many islanders have relocated, are relocating, or will relocate anytime soon (take your pick, none of these claims are ever substantiated), on the other hand some AGW sceptics claim (without proof, there is none) that sea levels there haven't risen in the past, and by implication or statement, that they therefore won't rise much, if at all, in the future.

There's also a more sanguine, realistic, and balanced view of the situation, from those who actually scrutinise the data, and take the longer view. I'm one such who believes that data is truth, analysis is interpretation, and that the "longer view" is aided by longer datasets. The Australian National Tidal Centre's "South Pacific Sea Level and Climate Monitoring Project" does a great job measuring and archiving sea level and climate data for many Pacific islands - their data forms the foundation of my South Pacific Sea Level reference page (sidebar top). However, their record is relatively short, and can give an inflated view of sea level rise in many cases. For example, the chart for the southern Cook Islands island of Rarotonga shows a rate of 5.25 mm/year rise to end 2011. Many of the NTC gauges on the Pacific islands were completely new installations, but the one on Rarotonga replaced an earlier gauge which recorded from 1977. The NTC doesn''t archive data for the older gauge, but PSMSL does, along with a slightly out-of-date record (end 2011) for the new gauge (updated to April 2012 from NTC data), and here are both plotted together:

The trend lines show that short-term data can give very different impressions of trends, even more emphasised when the slightly adjusted (-40 mm) earlier data is spliced onto the start of the later:

 .... when a much lower trend than either emerges. I've another reconstruction under construction (ouch!) which will show an even more interesting past (and a possibly less than interesting future, that's a good thing!) for another island in the area.

Data sources:
Rarotonga 1977-2001
Rarotonga B 1993-2011
Rarotonga 1993-2011 (NTC)

Making it up (2) - "Sea level 'rising fastest in SW Pacific"

Here we go again! A tranch of syndicated articles, or variation on same, which take a straightforward analysis of proxy data (which is from the past, by definition), and transpose its findings to the present or even the future. The cited paper is "Nineteenth and twentieth century sea-level changes in Tasmania and New Zealand", Gehrels et. al., though of course it takes either a site search, or a Google search to actually find an abstract, as it's just vaguely referenced, or the journal main page is given. As I've said before, this gives the distinct impression that the article authors would prefer we accept their take on it, without the benefit of reading the paper and making up our own minds. In this case, that would instantly debunk their alarmist conclusions, and in several cases, reveal that the authors either can't read and comprehend, or can but distort or even make up conclusions, effectively putting words into the mouths of the paper's authors. The abstract says

Positive deviations from linear sea-level trends represent important climate signals if they are persistent and geographically widespread. This paper documents rapid sea-level rise reconstructed from sedimentary records obtained from salt marshes in the Southwest Pacific region (Tasmania and New Zealand). A new late Holocene relative sea-level record from eastern Tasmania was dated by AMS¹⁴C (conventional, high precision and bomb-spike), ¹³⁷Cs, ²¹⁰Pb, stable Pb isotopic ratios, trace metals, pollen and charcoal analyses. Palaeosea-level positions were determined by foraminiferal analyses. Relative sea level in Tasmania was within half a metre of present sea level for much of the last 6000 yr. Between 1900 and 1950 relative sea level rose at an average rate of 4.2 ± 0.1 mm/yr. During the latter half of the 20th century the reconstructed rate of relative sea-level rise was 0.7 ± 0.6 mm/yr. Our study is consistent with a similar pattern of relative sea-level change recently reconstructed for southern New Zealand. The change in the rate of sea-level rise in the SW Pacific during the early 20th century was larger than in the North Atlantic and could suggest that northern hemisphere land-based ice was the most significant melt source for global sea-level rise.

That seems straightforward - sea level at the sample site rose at a relatively high rate (compared with the global rate) between 1900 and 1950, and a relatively low rate for the rest of the 20th century. Nothing to worry about then? Not according to several reports from "down under", whose almost identical articles, begin News.com.au (Australia):

SOUTHERN Australia and nearby Pacific nations are likely to be the most seriously affected in the world by the continuing rise in sea levels, according to new research.

... and 3 news (new Zealand

The seas around New Zealand and Australia are likely to be the most seriously affected in the world by the continuing rise in sea levels, according to research on Tasmanian swamps.

"According to research"? Apparently not, the paper abstract doesn't mention the future - remember that the paper's titled "Nineteenth and twentieth century sea-level changes in Tasmania and New Zealand". However, all the articles I've seen quote one of the authors, Patrick Moss:

"Sea levels in Tasmania remained relatively stable for much of the past 6000 years, but around 1880 they started rising drastically," said Dr Moss, who co-wrote the study in conjunction with scientists from the UK, New Zealand and Australia. 

From several reports:

Sea levels in the southwest Pacific rose at four times the average 20th-century rate between 1900 and 1950, according to the study.That was followed by a period of “relative quiet” broken by a second spike in 1990 which saw sea levels rise at a rate that defied projections.”The natural climatic factors seem to be not as apparent and anthropogenic climate change seems to be the key possible culprit,” said Moss.

and

Dr Moss said a jump in sea levels occurred after 1990.

"The rise in 1910 probably reflects the end of the little ice age, when temperatures were about one to two degrees cooler in the northern hemisphere than today," he said.

"The 1990s peak is most likely indicative of human-induced climate change."

Sounds rather like someone with an agenda - that conclusion's not in the paper. Why does he call it a "peak"? Because that's what it is, and both his sediment proxies and tide gauges in the SW Pacific generally show a decline since. The diagrams in the paper clearly show that. You have to follow the pea as the cups are moved, and analyse every word, or you might, as these web authors clearly have, assume the "jump" is still in progress. Elsewhere he says "A large ice-melt is like a fingerprint". There's that word again - if there's been a decline since the 1990s, then the "fingerprint" is rather blurred, and the "points of identity" are insufficient to identify the culprit. More to the point, what exactly was the "fingerprint" of the early 20th century rise? Here's yet another researcher putting his mouth where his paper isn't, and confirming our suspicions of his prejudice and unjustified conclusions.

What about that "lack of comprehension" I mentioned at the beginning? here's a good example from "Adelaide Now" - first the bogus prediction based on no evidence from the paper, nor its self-appointed spokesman (not the lead author), Moss

SOUTHERN Australia and nearby Pacific nations are likely to be the most seriously affected in the world by the continuing rise in sea levels, according to new research.

Then the silly error, repeated in several reports, including Planetsave (save it for whom and from what?)

Sea levels have risen approximately 20 centimetres in the South West Pacific Ocean since the end of the 19th century, a dramatic increase according to a new study released this week.

Scientists found that sea levels in Tasmania remained relatively stable for most of the previous 6,000 years but that around 1880 they started to rise dramatically. Between 1900 and 1950 the sea level rose at an average rate of 4.2 millimetres per year. The highest rates of sea level rise occurred in the 1910s with an increase of .3 to .8 millimetres per year, followed by a second peak in the 1990s.

If sea level rose 20cm since the late 19th century, and if the rate of rise between 1900 and 1950 was 4.2mm a year, which amounts to 4.2 x 50 = 210mm or 21cm, can we deduce it's fallen by 1cm since 1950?

I might add that I can see nothing like a rise of 4.2mm since 1900 for tide-gauges in the southern part of Australia, nor any "spike" in the 1910s. Perhaps I'll update this post with a few charts to illustrate that.

Vancouver, Canada - are "planners" trying to frighten residents?

The decidedly warmist  Vancouver Sun has the story "South Delta faces rising threat from floods":

South Delta will be vulnerable to disastrous flooding in the coming decades without wholesale adaptation to rising sea levels.

Speakers at a science symposium in Vancouver on Sunday said projections of a one-metre rise in sea level are too conservative – and that continuing international failure to deal with global warming likely means a “multi-metre” rise in ocean height by the end of this century.

For 21,000 residents of Ladner, a low-lying suburban community that fronts onto the south arm of the Fraser River near its confluence with the Strait of Georgia, that means an urgent need to protect the community from flooding.

Waterfront homes, inland suburban developments, roads and farmland are all vulnerable to a sea level rise of 1.2 metres, according to research presented by David Flanders of the University of B.C.

Flanders, along with Simon Fraser University professor of geology John Clague, were featured local speakers at a symposium for the annual convention of the American Association for the Advancement of Science, which continues through today at the Vancouver Convention Centre.

So a "projected" rise, to be expected decades into the future means there's "an urgent need to protect the community from flooding"? Which disaster blockbusters have these "scientists" been watching? And there it is again, a global estimate for sea level rise is applied directly to a single location in Canada. As with "projected" future temperature, no allowance or adjustment is made for local conditions. Just what are the "local conditions" near Vancouver? I know that seal level rise along the Pacific coast of North America decreases with increasing latitude: the further north, the lower the rate of rise. It's due to "isostatic rebound" - land covered by ice sheets during the last ice age is slowly rising, and has been since the ice started to melt and generate much of the sea level rise since then.

What I found surprised even me; as far as I know it's almost unique.

Sea Level at Vancouver, BC 1910-2010   data source: PMSL

The trend over 100 years is just 0.31 mm year. We're repeatedly told that the global rate of rise has accelerated over the later decades of the 20th century; no sign of that here. The last three decades encompasses the "satellite era" towards the end of which satellites have been monitoring an apparently accelerating rise in sea level:

Sea Level at Vancouver, BC 1980-2010   data source: PMSL

That looks pretty flat to me - if I were Peter Gleick I might say that it was a downward trend, but then I doubt he would ever present and discuss a downward trend in anything other than rainfall. Statistically it's a slight fall, but too tiny to draw any conclusions. The 1982/3, 1997/8 and 2010 El Niños are clear on the first chart, less so on this one, but still distinguishable in the broad, tall upward spikes.

It seems that the worthy citizens of South Delta (a southern coastal suburb of Vancouver) are safe in their beds for a while yet. Did David Flanders and John Clague present this information at the AAAS symposium? I can find no record of them having done so, but then this was an American Association for the Advancement of Science event, not the American Association for the Advancement of Truth.

South Pacific Sea Level 2011 - updated

The South Pacific Sea Level  reference page (top of sidebar) is now updated to the end of 2011. I've given the charts a new look, with a 13-month moving average added where appropriate to give a clearer view with the "spikiness" filtered out. Here's a sample for Nauru, where the red line shows a clear downward trend since 2001/2

Seal Level at Nauru, 1993-2011

If you've any comments, leave them here, as comments aren't active on fixed Blogger pages. I'm working on a similar page for Australia, which will include rather more stations than Australia's CSIRO seem to recognise exist (see here below), and will definitely include Hobart, Tasmania. You'll know why if you've read that post.

Blogger Strikes Again

Apologies to those who viewed the South Pacific Sea Level to September 2011 post recently. I corrected a chart heading a while ago, and Blogger decided (yet again) it didn't like my HTML for the interactive map feature, and simply removed the relevant code. Luckily the sidebar reference page (top right on the sidebar) was unaffected, though I'd made an identical correction to it. The feature's now reinstated.

That reference page will be updated soon with charts to December 2011, in the new style I've been using recently with a 13-month centred running mean. I think that gives a much clearer indication of "what's been happening" on charts which show much greater variation in levels than is usual worldwide. If anyone has any constructive comments on presentation I'd be glad to receive them. To anyone who thought this post's heading would lead to an exposé dealing the dirt on some other blogger, I apologise.

The Footprint of El Niño - South Pacific Sea level

I've mentioned the intermittent effect of El Niño on South Pacific sea level in several posts. How and why does this part of the ENSO cycle affect sea level?

The primary cause of anomalous ocean conditions is the El Niño/Southern Oscillation (ENSO) in the equatorial Pacific Ocean. Westward winds normally maintain slightly higher water levels in the western Pacific relative to the eastern Pacific. Every three to five years, in a non-periodic pattern, the winds weaken and water levels in the western Pacific drop below normal. The southern equatorial current is weakened and water temperatures in the eastern Pacific rise. This condition is known as El Niño. The opposite condition, known as La Niña, occurs when westward equatorial winds are unusually strong and water levels in the western Pacific become anomalously high. The south equatorial current strengthens, accompanied by below normal water temperatures in the eastern Pacific.

Boiled down, in terms of the effect on sea level, is that levels in the western and south-western Pacific tend to drop, often significantly, during El Niño years, while those in the east tend to rise.

The island of Majuro, in the Marshall Islands reflects this trend particularly well. The opposite La Niña effect, though present, is not so well illustrated. Using data from an earlier gauge maintained by the University of Hawaii, and the later SEAFRAME gauge installed in 1993 by the National Tidal Centre based in Adelaide, Australia, I've been able to reconstruct a history of sea level at Majuro Atoll from 1978 to 2011.

For charts for Majuro and other Pacific Islands, including Tuvalu and Kiribati, see my reference page "South Pacific Sea Level 2011".

Here's a table of El Niño years. Those from 1969 to 2010 are clearly represented on the Majuro chart. The 1982-3 and 1997-8 El Niños were particularly strong events, and I've highlighted them in red

El Niño Years 1902-1903 1905-1906 1911-1912 1914-1915 1918-1919 1923-1924 1925-1926 1930-1931 1932-1933 1939-1940 1941-1942 1951-1952 1953-1954 1957-1958 1965-1966 1969-1970 1972-1973 1976-1977 1982-1983 1986-1987 1991-1992 1994-1995 1997-1998 2002-2003 2006-2007 2009-2010

On the other (eastern) side of the Pacific, continuous long-term records are difficult to find, but that for Monterey, California illustrates the opposite effects quite well, although earlier El Niño years aren't quite so clearly defined.

Not much sign of the 1972-1973 and 1976-1977 El Niños, but the later events are all represented, though to varying degrees. Most of the west and south-west Pacific islands show the "El Niño" effect to differing degrees, but Tuvalu has become the "poster child" of the Global Warming scenario, so it's worthwhile reproducing my reconstruction for that island, covering 1977-2011.

The linear trend shows a value of 0.28 mm/month, which translates to 3.36 mm/year. However, the effect of the El Niños is to pull the trend line down progressively from right to left; it's always below the 13-month running mean (in red), more so on the left. A simple way to eliminate the negative effect of the El Niño "spikes" on the trend is to remove them from the data. However, this is not as easy as it sounds; there's a clear (approximately) annual cycle, illustrated by the sharp upward spikes.  These "king tides" usually occur in late February or early March, occasionally as late as April, and their timing is due to the "lining up" of the tidal effects of both moon and sun. The all-time peak was in February 2006 (very clear on the graph), and despite dire predictions, hasn't yet been surpassed.

An Australian newspaper dispatched a team to Tuvalu in February 2011 to document what was expected to an all-time record "king tide". However, nature being as quirky as ever, organised things so that they'd already "missed the boat" (a metaphor becomes a bad pun!) as the highest tide had already occurred the previous month; indeed the February peak was lower than both January and March peaks. That and the fact that the January peak was no record, produced a "non-event" and no follow-up report was published.

However, I digress - removing the El Niño "spikes" must be done with care if an opposite upward bias is to be avoided. One way round this is to use annual data so the monthly cycle is not a problem, though it effectively removes more data. I'll be following up with a detailed analysis of late-20th century sea level rise at Tuvalu.

Data Sources


Marshall Islands (Majuro): Permanent Service for Mean Sea Level and South Pacific Sea Level and Climate Monitoring Project

Monterey: Permanent Service for Mean Sea Level

Tuvalu (Funafuti): Permanent Service for Mean Sea Level and South Pacific Sea Level and Climate Monitoring Project

South Pacific Sea Level to September 2011

Note: A permanent and (to be) regularly updated page has been created (see top of sidebar) located here. I've updated this page with data to December 2011.

The island sea level charts are drawn from monthly data from the South Pacific Sea Level and Climate Monitoring Project. I've included a chart for a second Fiji station, and also one at the end for a New Zealand station, Jackson Bay (South Island). Neither is part of the project, but data is provided on the website.

The high resolution SEAFRAME (Sea Level Fine Resolution Acoustic Measuring Equipment) monitoring stations comprise modern integrated housings which measure and record sea level, barometric pressure, water temperature and air temperature. Most of the stations were installed in 1992 and 1993, though a few were later. It's important to note that the effect of local land movement is eliminated from sea level data:

The Continuous Global Positioning System (CGPS) network monitors vertical movement in the earth's crust, such as subsidence or tectonic shifts, at the SEAFRAME tide gauges and adjacent land. Sea level data can then be adjusted to compensate for the earth's movement to within a millimeter, enabling the absolute sea level to be determined. 

I have voiced criticism of Australia's Bureau of Meteorology on various topics in the past, but as far as the presentation of sea level data is concerned, I rate their National Tidal Centre as the best. The page I linked to above has a table of the 12 stations in the project (and the two others I mentioned) which links to PDF plots and data tables for sea level, barometric pressure, water temperature and air temperature. The data tables in turn link to online graphical plots and text files for easy import to spreadsheets. A map links directly to the data tables. I liked that Idea so much I've pinched it for use here.

What should be evident from the plots is that any generalisation of the situation over this wide area is invalid. Apart from an almost universal downward spike during the 1997/98 ENSO event, the history and trends differ widely. It should also be clear that claims of "25 mm/year" or "no rise" since the early 1990s are also invalid.

Most of the charts are dominated by a downward "spike" in 1997/98. The level drop was due to unusually high barometric pressure during the 1997/98 ENSO ("El Niño/La Niña-Southern Oscillation") event. The correlation is well illustrated for the Marshall Islands (Majuro Atoll), so I've placed this first. Kiribati and Tuvalu have been given much attention in the news media and on the 'net recently, so they're listed next.

Readers are welcome to reproduce any of the plots - all I ask is that attribution be given, preferably with a link to this post. I haven't used thumbnails - right-click on the image and select "save image as" or whatever your browser prompts.

Level data has been converted from metres to millimetres to overcome loss of precision in Excel's trend data. Gaps in the plots indicate gaps in the original data. Note that the trend slope is monthly - multiply by 12 to get the annual value (e.g. y = 0.2269x gives 2.7228 mm/year).

Select a location from the map to view a graph of the monthly sea level statistics for that location. Click on the bottom of the blue area for the NZ station, Click on your browser's back button to return to the map.

Source: Bureau of Meteorology     

Marshall Islands

Island: Majura   Location: Uliga

Note the 1997/98 ENSO "spike" and the correspondence with the abnormally high atmospheric pressure from late 1997 to late 1998 shown in the barometric pressure plot below:

Kiribati

Island: Tarawa   Location: Betio

The trend line is pulled down by the ENSO dip from the end of 1997 to end 1998. To give an better view of the trend from 1992 to present, I replotted the chart with that data excluded:

The resulting trend is effectively zero.
A downward trend is evident from end 2001 to present:

Tuvalu

Atoll:Funafuti   Island: Fongafale

As with Kiribati, the deep ENSO dip in 1997/98 pulls the trend line down on the left; it's below the 1994/1997 average. A zero trend is evident from 1999 to present:

Papua New Guinea

Island: Manus   Location: Lombrum

Here's a clearer view of the 1999-2011 trend of 3.4 mm/year, slightly above the global average:

Solomon Islands

Island: Guadalcanal   Location: Honiara

Again the trend is pulled down on the left; the average level 1999 to present is around 750 mm, and the trend 2.1 mm/year.

Vanuatu

Island: Efate   Location: Port Vila

The big 1997/98 downward spike evident in most of the other plots is absent; instead there's a relatively steady upward trend.

Fiji

Island: Viti Levu   Location: Lautoka

Island: Viti Levu   Location: Suva

Tonga

Island: Tongatapu   Location: Nuku'alofa

Although there's a steep trend from 1993, current levels are not dissimilar to those between 2000 and 2003.

Cook Islands

Island: Rarotonga   Location: Avatiu

Levels seem to have stabilised from 2006.

Samoa

Island: Upolu   Location: Apia

The familiar ENSO dip pulls the trend down at the LHS, but there is a sharp upward "spike" from 2010.

Nauru

Island: Nauru   Location: Aiwo

Overall trend is effectively flat - levels at present similar to those in 1993. However, the trend from 2002 is downward.

Federated States of Micronesia

Island: Pohnpei   Location: Dekehtik

An overall upward trend, though little change from 2007 to present.

New Zealand

Island: South Island   Location: Jackson Bay

There seems to be little overall change from mid-1998 (after the ENSO dip) to present. A plot from 1999 confirms that: