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.

Sea-level in Australia and the Southern Oscillation Index

I've read a fair bit about the Southern Oscillation Index (SOI) over the years, about how much ENSO (El Niño/La Niña Southern Oscillation) affects sea-level in the Pacific. I've noted effects, particularly the El Niño "dip" in the western and central Pacific, and the corresponding "spike" in the east (especially the US Pacific shore). However, my impression was that it was just the extremes, El Niño and the less-well defined La Niña that had any real effect on Pacific sea-level. Before I continue, it's worthwhile quoting what Australia's Bureau of Meteorology has to say about the SOI; it's succinct and informative:

The Southern Oscillation Index, or SOI, gives an indication of the development and intensity of El Niño or La Niña events in the Pacific Ocean. The SOI is calculated using the pressure differences between Tahiti and Darwin.

Sustained negative values of the SOI below −8 often indicate El Niño episodes. These negative values are usually accompanied by sustained warming of the central and eastern tropical Pacific Ocean, a decrease in the strength of the Pacific Trade Winds, and a reduction in winter and spring rainfall over much of eastern Australia and the Top End. You can read more about historical El Niño events and their effect on Australia in the Detailed analysis of past El Niño events.

Sustainted [sic] positive values of the SOI above +8 are typical of a La Niña episode. They are associated with stronger Pacific trade winds and warmer sea temperatures to the north of Australia. Waters in the central and eastern tropical Pacific Ocean become cooler during this time. Together these give an increased probability that eastern and northern Australia will be wetter than normal. You can read more about historical La Niña events and their effect on Australia in the Detailed analysis of past La Niña events. 

The ENSO Wrap-Up includes the latest 30-day SOI value, as well as other information on indicators of El Niño and La Niña events.

 The graph below shows monthly values of the SOI in recent years.

  Source:BOM

On the following page they have links to data tables; Wanting to create a spreadsheet of monthly SOI values (from 1876!) I was dismayed to find the table to be structured as years down and months across. However, using Excel's Copy and Paste-Special/Transpose functions I was able to do it, laboriously year by year. Here's the result for 1959 to May 2013. The reason for the not-so-obvious start year will become obvious very soon.

SOI index 1959-2013    Data source: BOM

I've added a 25-month (2 year) centred moving average to smooth out the spikes without suppressing the signal. A 13-month MA would seem to be more appropriate, but gives too "lumpy" a trace; a 37-month MA smooths just too much. Like Goldilocks' porridge the 25-month MA is "just right".

Comparing the SOI plot with a sea-level plot is easy, but I wondered if I could add the SOI to a sea-level chart in some way. One problem is that the signal is relatively small, and the other is that it varies around a (flat, obviously) zero value. I hit on the wheeze of "magnifying" the SOI signal, and normalising the start of the SOI moving average with the start of the sea-level moving average, incrementing the magnified SOI by the monthly sea-level-trend increment. I tried a factor of 10 for magnification, on the basis that the SOI signal is based on air pressure at sea level, and one hPa change leads to a 10 mm sea-level change (in the opposite direction). My assumption may not have had much maths behind it, but the "porridge effect" operated and it was "just right". Here's the result for Darwin:

Darwin complete sea-level record 1959-2012       Data source: BOM/NTC

I don't now what you think, but I'd call that a rather good correlation, especially over the right-hand half of the chart. Here's one for Fremantle over the same period.

Fremantle sea-level 1959-2013  Data source: BOM/NTC

For both Darwin and Fremantle, note that the recent (since 1994) sharp upward trend has begun a downward reverse, more clearly predicted on the SOI chart which extends to last month (May 2013). The large and broad downward bulge around 1983 corresponds with the intense (some would say most intense on record) El Niño of 1982-3. It shows up well on the 25m MA sea-level plot for Darwin (and most Australian stations), but sea-level rose at Fremantle during that event. All the other El Niños show up on both charts; the broad low during the early 1990s (1991-2 and 1994-5 El Niños, with just 1993 between) and the intense but shorter 1997-8 El Niño. The 2010 El Niño was a more subdued affair.

I think it's clear that the SOI doesn't just affect variations in sea-level, it drives them, at least on the west coast of Australia. In a future post I'll look at other Oz stations for correlation, and where correlation is poor, explore possible reasons.

The Nodal Tidal Cycle - more evidence

You've probably never heard of Port Pirie. It's a mining town and port (really?) in South Australia, north of Adelaide, though Australians might call it a city. In common with many ports in Australia it has a tide gauge.

Nothing very spectacular to see there, just a pronounced dip caused by the intense 1997/8 El Niño, followed by a step rise and a relative stasis, and a low overall rate of rise. Apart from the lesser dips going back to 1969, all caused by previous El Niños, there's no obvious signs of any cycles in the data. That data provided by the BOM's National Tidal Centre, has a standard deviation included for the hourly data which is averaged to create the monthly averages plotted on the chart. The standard deviation reflects the variability of the hourly data through the tidal cycles, and that variability is increased or reduced by the effect of the 18.61-year period of the nodal tidal cycle (NTC). If the standard deviation is plotted something quite spectacular appears.

Proof if any is still needed, of the lack of any great influence of the NTC on mean sea-level. Using the standard deviation to show the effect of the NTC on tidal variability is a technique I'd like to be able to claim as my own invention, but I have to give all the credit to one David Pugh, author of several excellent books on things tidal. It's obvious when you think about it - I just didn't think about it - doh! In common with other regions worldwide, some Australian stations show the cycle clearly (Port Pirie is just the clearest example) and some don't. Fremantle in Western Australia is another Oz station which clearly shows the cycle; it has a much longer record than Port Pirie, and the cycle has an evident upward trend. First the gauge record -

..... and the standard deviation showing the NTC -

Note the obvious upward trend - this doesn't indicate any marked effect on mean sea-level, but shows that the tidal range, the difference between low and high water, is increasing somewhat. I don't know whether this is a feature of west-coast sites or not, but Sydney on the east coast shows a much steeper downward trend. What the cause of these trends might be, I don't now, and I can't find any literature which might throw some light on it. Perhaps there's something here waiting to be discovered.

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".

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).

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

Australia's CSIRO - manufacturing sea level hockeysticks?

The CSIRO's "State of the Climate" report was published today (14th March 2010). Missing a link to the report in the newspaper article summarising the dire consequences of climate change in store for Diggers Down Under, I did a Google News search, and came up with a rather interesting ABC page on the release of the report, titled "Sea Levels are Rising", which is not exactly news, but never mind that. Below the obligatory (and of course irrelevant) statement

It notes that the long-term warming trend has not changed, with each decade having been warmer than the previous decade since the 1950s.

... is an "interactive data visualisation" which "explores sea level rise patterns across Australia using data sets provided to the ABC by CSIRO". What struck me immediately was the uptick in sea level at three of the 62 tide gauge stations on the superimposed charts below the interactive map. I've selected Wyndham (WA) on the map - which shows the largest 2010 uptick. I've almost completed an interactive map for Australia myself (similar to the "South Pacific Seal Level 2011" in the reference pages, top-right sidebar), so I'm familiar with the chart for Wyndham. That uptick is definitely not kosher, not kosher at all. here it is:

Source: ABC

... and the RHS embiggened:

Source: ABC

By reading the data points from the ABC chart, I've established that all the preceding annual data points are correct, but 2010 stands out like a sore thumb Here's the corresponding chart for Wyndham, over the same time period, 1993-2010, with the last two points from the ABC chart added in red:

Data Source: NTC

The lower pair of points are Darwin (346) and Carnarvon (322). If the offsets from the real data for all three stations are added, they total 526, which averaged over all 62 stations comes to 526/62 = 8 mm rounded down. If that's deducted from the all-station average for 2010 (dark green line), it brings it down from 120 mm to 112, which means that the three outliers have increased that 112 figure by almost 11%.

I considered whether this might not be deliberate fiddling (generous and understanding to a fault!), but possibly a result of using incomplete data for 2010, for example January-June, but that doesn't explain it - any average with January as a start point is much lower than the ABC/CSIRO figures. Not only that, but 2009/10 were El Niño years, and there's usually a drop in sea level during one of these events; it shows up (though much less pronounced than 1997/8) at most stations except some in the far south. One such rogue plot might be a genuine error, but three? Here are my plots for Darwin and Carnarvon:

Data Source: NTC

Data Source: NTC

I've checked a random sample of the other stations on that rather clever (I'm green with envy - don't take that as weakness) interactive page, and can detect no further excursions from NTC data whatsoever, even for Hobart, home of the CSIRO. Currently, this is a mystery within an enigma, to paraphrase Churchill's description of Russia at the beginning of WW2.

UPDATE 15th March 2012

I've tracked down the source of two of the "adjustments". The CSIRO (funded by the Australian taxpayer) doesn't obtain its sea level data from the National Tidal Centre (funded by the Australian taxpayer, and where you'd expect them to get it as I do), but from an independent archiver, the Permanent Service for Mean Sea Level, based in Liverpool, UK. It's one which I use regularly for data unobtainable elsewhere, but I'm surprised that the CSIRO uses it. The PSMSL relies on data submission from national or other bodies which collect it, and it's rarely up-to-date, often months or even years of the latest data are missing. This explains why CSIRO web pages and publications quote sea level statistics up to Dec. 2010 for the NTC SEAFRAME stations, even though the NTC publish the data monthly.

Anyway, PSMSL has, apparently arbitrarily, adjusted 2010 monthly data for Carnarvon and Wyndham upwards by 140 mm and 260 mm respectively, with no acknowledgement (as is customary) on the station pages. here's a chart for Wyndham for 2009-10 illustrating what's been done:

Data Sources: PSMSL & NTC

That 260 mm is larger by 63 mm than the change in sea level at Wyndham since the gauge was installed in 1966, and larger than estimates of global sea level rise since 1900, so it's no small matter. What are they playing at? The Darwin data (to 2010) at PSMSL appears to be identical to the NTC data (except measured from a different baseline, which is irrelevant), so where did that 128 mm adjustment come from? Sherlock is on the case, with his (t)rusty magnifying glass at the ready. No violin though. On second thoughts, perhaps I'll just ask them. Watch this space for exciting developments.

San Diego - time to get worried?

The powers-that-be in San Diego, California are getting worried about sea-level rise.

Buildings, shoreline parks and recreational facilities, transportation systems, and energy and water facilities are at risk, regional groups said Thursday.

So says U-T San Diego "Plan for sea-level rise in San Diego Bay". The article begins

A coalition of local agencies on Thursday announced one of the nation’s first regional plans to prepare for sea-level rise. Focused on San Diego Bay, it’s designed to help the region adapt to one of the more visible aspects of climate change.
Sea level could rise by as much as 17 inches by 2050 and five feet by 2100, when many areas around the bay could be permanently inundated, according to a recent assessment. The greatest cause for concern is the likelihood of increased frequency and severity of flooding during storms or very high tides.

I notice the neither the current nor past rates of sea-level rise at San Diego are mentioned. The  "coalition of local agencies"  doesn't seem to think it matters,  in common with most such organisations worldwide. It's not clear where the "17 inches to 5 feet" comes from, it's not mentioned in any of the sources I've read. However, Google gives a source for that phrase on Wired, and that article links to Think Progress - where else? Our Joe says 
 Arctic Assessment bombshell: “Global sea level is projected to rise by 0.9“1.6 meter by 2100″. I don't know why there's a strange character (in the title, not our Joe) between the 9 and 1, should be a dash I assume. Anyway, the 5 feet would seem to be a global estimate, so here as elsewhere, planners assume a global prediction rather than get a local estimate.

The analysis was supported by Port of San Diego, San Diego County Airport Authority, The San Diego Foundation and ICLEI–Local Governments for Sustainability USA. Chula Vista, Coronado, Imperial Beach, National City and San Diego also helped develop the strategy.

So that's alright then - these august bodies can surely be trusted to use taxpayers' money in a timely and efficient manner to protect beaches and seafront dwellings, businesses and roads. Romm cites the Arctic Monitoring and Assessment Programme's "Snow, Water, Ice and Permaforst in the Arctic" report. That's not my typo - it's copied from their website. Anyways, it's a global figure, as I said, and quite likely may over- or understate the situation for San Diego. So what is the situation for San Diego? The local tide gauge tells all, from 1906 too.

San Diego Sea-level from 1906-2010  Data Source: PMSL

 No spectacular acceleration evident there, in fact it looks like it's levelling off:

San Diego Sea-level from 1990-2010  Data Source: PMSL

 That seems pretty level to me, but of course I'm not Peter Gleick. He can see the horizon sloping upward from left to right. Those spiky graphs are hard to digest, so let's see if the annual average removes the noise.

San Diego Sea-level - annual average 1906-2010

 That's interesting, if my Mark One Eyeball doesn't deceive me, the 11-year moving average has levelled off after about 1987. One sure way of finding out is to plot the calculated trend over a period of years, for example from 1906-1970, then 1906-1971 and so on.. It's called asymptotic analysis, where the plot might move up and down, but settles at near the true rate as the finish year approaches the end year (here, 2010).

San Diego - evolution annual sea-level trends

 Now that's interesting too -the sharp rise from 1982 is a result of the sharp upward El Niño spike seen in the first chart. There were two large spikes in the El Niño years of 1992-3 and 1997, and these show in the rate change above. However, the rate declined after 1998, and still seems to be dropping. It's lower than it has been since 1983, the second year of the largest spike in the first chart. Bear in mind that a decreasing rate doesn't necessarily indicate declining sea-level, the overall rate is still positive to the end of the trend chart. But the rate is still decreasing, and we've seen that there's been no net rise since 1990.


Gazing into the future is pointless unless your feet are firmly anchored in the present. No bank would advance money solely on the basis of future projections of income. They want to see your current financial situation, and past figures too, in order to assess the validity of those projections and therefore the risk. Is the "coalition of local agencies" listed above even aware of the current "plateau" at San Diego? If not, why not?

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: