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RUTI: Coastal temperature stations

Posted by Frank Lansner (frank) on 13th October, 2011
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See this article in Joanne Novas long version version including debate

See full article at


RUTI: Coastal temperature stations

Fig1. World wide comparison coastal/Island temperature trends vs. non-coastal trends from RUTI (Rural Unadjusted Temperature Index)

In the following it is shown, that temperature stations from coasts / islands generally have significantly different temperature trends than near by non-coastal temperature stations.

The focus of this writing is coasts world wide where land (from continents or Islands) meets the three large oceans (The Pacific, Atlantic and the Indian ocean) directly. For this analysis, 35 areas where land meets these oceans where used as studycases. They represent nearly all possible such areas where data is available.
Further more it is shown, that often coastal temperature stations have more heat trend before 1950 than the near by non-coastal stations.

Some consequences hereof:

- Coastal temperature stations are unreliable as indicators for non-coastal areas and vice versa. Often, the warmer trended coast/island area is just a fraction of the total land area and resembles the sea surface trend rather than the land based trend.

- Coastal stations ought not be used for long range smoothing over land areas (or vice versa).

- Adjustments where a non-coastal station are changed to look more like a coastal station (or vice versa) should be avoided.


Data used in this writing - like all RUTI writings - are from unadjusted GHCN. When analysing unadjusted GHCN data in general (for the RUTI project), I repeatedly experienced that temperature stations placed on islands or on the coast or very near the coast had very similar trends, but this trend was significantly different from the trends from temperature stations in the very same area, but just a little further from the coast. Sometimes just 10-20 km makes all the difference.

Since temperature trends obtained from Islands or coast stations are generally very similar, these coastal/island stations are likely to be dominated by the Marine air temperature trend.

Raw average of the 35 study cases using 1961-1990 as baseline, dots are one year and lines are 5 year averages:


Fig2: Worldwide raw average of coastal vs. near by non-coastal temperature trends from the 35 study cases representing nearly all places on Earth where we can directly compare large-ocean trends and non-coastal temperature trends (from the very same data source).

! ! The “beauty” of comparing coastal vs. non-coastal stations from the very same source (GHCN-Unadjusted) is, that whatever adjustment you might find necessary for temperature data stations in general there is no adjustment type that is dependant on a coastal or non-coastal location. Therefore differences approximately as shown in fig2. coastal vs. non-coastal both from Unadjusted GHCN tells a story that is more likely to be somewhat true.

Fig2a. Comparison with Raobcore (30S-30N) tlt. Representing half the globe, and around 2 thirds of the area where it was possible to make the 35 study cases. Both land (non-coastal) and ocean (coastal) trends from this writing appears to produce results rather similar to Raobcore data 1958-2008. Raobcore trends are similar to UAH and RSS satellite trends after 1979.


See this article in Joanne Novas long version version including debate

See full article at

Many more RUTI writings and results, see links at the end of this writing

Last changed: 14th October, 2011 at 17:57:14



After 1955-60.. By Unknown on 16th October, 2011 at 22:48:37
Hi there!

I can only guess howcome trends are smilar after 1955.
On this figure
AMO, PDO and solar activity are shown qualitatively just to get an idea of some possible mechanisms.

In general, coastal/Ocean temps happens to follow solar activity best while non-coastal/land temp trends follows PDO best.

And.. after around 1960, there is some similarity between PDO and Solar activity.

I have no idea if this is just random, but to some degree the "equation" would make sence if Solar Activity had most impact at sea while the oceanis PDO pattern eventually has largest influence on land temperatures.

? But this is obviously just speculation :-)

K.R. Frank Lansner
What changed By Unknown on 16th October, 2011 at 15:21:07
Frank what happened around 1955, why do the two traces coincide from that period onwards?
Hi Juergen! By Unknown on 14th October, 2011 at 21:10:06
Yes in fact i did see these data, and in some cases this dutch database actualy can provide data not available from GHCN.

BUT! In many (most) cases on this database i have experienced, that data are strongly (warm) adjusted, sadly, and thus seems to nearly useless in my search for original data series. Also in many cases not all years are shown :-/

Thanks for input!!!!!
K.R. Frank Lansner
Climate Data Europe By Unknown on 14th October, 2011 at 19:01:10
Hi Frank,

have you seen this?


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