Wednesday, 14 March 2012

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.

No comments:

Post a Comment