Thursday, June 11, 2015

Nick Stokes Goes There


A while ago the GWPF (yes, just as dumb as trying to pronounce Joe Btfspik) tried one on, claiming that they were going to conduct a "temperature data review".  Nick Stokes has made a habit, indeed a retirement of going there, in his own way, of challenging the ungodly in hell, or Climate Audit and the like, but Eli repeats himself.  Bunnies should read Nick's submission, but there is one paragraph that Eli would like to emphasize, because while it is obvious, it is so obvious that entire castles of fancy have been built on ignoring it

Global averages are averages of millions of individual readings. Unbiased noise is very heavily damped in the result. The big source of error is bias, which is not damped in the same way. The essential purpose of homogenisation is to identify and minimise this bias. The tradeoff vs added unbiased noise is advantageous, because of that damping. 
In short averaging handles noise, homogenization is necessary to take care of bias.

7 comments:

Oale said...

"Global averages are averages of millions of individual readings".

This might be fun for someone to calculate and verify. Nowadays with automated weather stations this is pretty much certainly true, but how many individual readings there are during a day? Sample rates of f.e. airport station thermometers are pretty high, no?

Matt M said...

Best terms of reference. Sometimes its like they are not even trying to be taken seriously

Russell Seitz said...

As to < a href ="http://vvattsupwiththat.blogspot.com/2015/06/kicking-bucket.html " > The Great Naval Bucket Race , I can but agree

caerbannog said...

A good chunk of that bias (possibly a majority of that bias, even) can be attributed to the movement of a bunch of temperature stations from urban centers to outlying airport locations during the mid 20th-Century.

The summary GHCN metadata information supplied by NOAA includes a flag that designates each temperature station as an "airport" or a "non-airport" station.

Drill down into the GHCN data/metadata, and you will find that hundreds of those GHCN "airport" stations have temperature data records that predate the very concept of an "airport".

It should be quite obvious (even to deniers, if you have the patience to explain it to them until they become clear on the concept) that those stations did not begin their lives at airports.

At some point, those stations were moved from (most likely warmer) urban locations to those newfangled airports in (most likely cooler) outlying locations.

Now if you take the GHCN raw temperature data (all stations), run it through a simple anomaly gridding/averaging algorithm and compare with the NASA "Meteorological Stations" index (aka NASA's GHCN-only temperature index), you will see a visible bias between your results and the NASA results. It's not a huge bias, but it's definitely visible.

If you repeat the above with the exception that you exclude all of the "airport" stations, you will see a visible reduction in that bias. Do the same but exclude the "non-airport" stations, and you will see a visible increase in the bias.

For those who are interested, some time ago I put up a post comparing results for "all GHCN stations" vs. "non-airport GHCN stations" on my hometown newspaper's on-line discussion board. (Did it for the lurkers, not the deniers). Here's the link.

That post was my modest attempt to "demystify" the concept of data homogenization.

There are a number of factors that homogenization corrects for; perhaps the easiest to explain to non-technical folks is the "station moves" factor (certainly easier to explain than "time of observation bias").

Dano said...

My question is: who among the conservatives is leading the volunteer recruitment to re-locate the planet's flora and fauna who were tricked into moving north (south) and up by the world's climate scientists' manipulating data? Who is leading the charge to re-alkaline the ocean? Unbleach the corals?

I see no such recruitment. Don't they care about the earth?

Best,

D

Russell Seitz said...

My question is: who among the conservatives is leading the volunteer recruitment to.... Unbleach the corals?


Me.

I'm working with UNEP coral preservationists to see if boosting water albedo on overheated reefs can mitigate hyperthermia

Hank Roberts said...


> Me.

> I'm working with UNEP coral preservationists
> to see if boosting water albedo on overheated
> reefs can mitigate hyperthermia

Visible from the satellite imagery yet?
The DSCOVR imagery can resolve contrails, so it ought to be able to resolve patches of microbubbles. Where can we look?