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Comparing Temperature Trends At Valentia & Shannon Airport

October 27, 2014
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By Paul Homewood     


We’ve seen how the GHCN record for Ireland is heavily reliant on airport sites, and that high quality rural stations such as Valentia have had artificial warming trends introduced via the homogenisation process, as they have been compared with urban sites.

How much difference might all this make?


We can compare the temperature records of Valentia and Shannon Airport, which are only 78 miles apart.


Bear in mind the following chart is based on the unadjusted GHCN temperatures.





It can be seen that the temperature trend at Valentia is much less than Shannon’s. Indeed. the latter is nearly 1C/century greater.



This is hardly surprising when you compare the two locations.

Valentia Observatory is a high class set up, with no urban influences.





On the other hand, Shannon Airport is Ireland’s third busiest airport, handling 1.4 million passengers and 18000 flights a year.



And it is certainly a far cry from what it looked like in 1961.




Looking at the longer term trends at Valentia, since 1930, we can see that temperatures in the last two decades are only back to where they were in the 1930’s and 40’s.

If the data does not support the theory, adjust it!





And to explain this cyclical pattern, you need look no further than our old friend, the Atlantic Multidecadal Oscillation. 






As I mentioned yesterday, GISS do make allowance for UHI, although there are major flaws in the process.

So how much do they allow for Shannon?

Since the station opened there in 1948, just 0.1C. Yes, that’s right, a measly 0.1C.

  1. October 27, 2014 6:37 pm

    Note that you can draw a binomial from 1950 to 2005
    showing the dip around 1975
    Like CET, Valencia runs opposite the global wave,
    due to the GH effect
    (more clouds, more warmth, usually during winter times)

  2. October 27, 2014 6:43 pm

    what determines how the AMO behaves?

    • October 27, 2014 6:57 pm

      There’s a lot scientists don’t know, but they do know the AMO is a natural phenomenon, going on for at least the last millenium.

      I believe it is partly tied into the AMOC. There are times when it speeds up, thus carrying warm surface water from the Tropics into the deep. At other times in the cycle, it slows down and the warmer water remains at the surface.

      There’s a good summary here.

      My belief is that oceans are by far the biggest drivers of climate, as they carry so much heat content, and are capable of moving it around the world.
      Remember too that ocean processes are much slower then other changes. Any changes we are seeing today would have been set in motion maybe decades ago.

  3. October 27, 2014 7:01 pm

    First question:
    Primarily, what heats the oceans, the most?

  4. October 27, 2014 7:37 pm

    but why does the amount of energy coming through the atmosphere vary?

    mostl;y two cycles

    • October 27, 2014 8:01 pm

      All I know is that about every 30yrs the AMO switches from cold to warm and back again. This in turn has a significant effect on NH temps.

      If NOAA and the rest can’t explain all the causes, I certainly am not going to try!

      • henryp permalink
        October 27, 2014 8:10 pm

        The question is as simple as asking what came first? You just want to make itr more complicated.

      • October 27, 2014 10:30 pm

        Why? I just report on the facts. I have not a clue what caused them.

        What do NOAA say when you told them your theory?

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