Tuesday, July 15, 2014

Why the satellite temperature data is infinitely better than the surface record

Long time readers know that I've been quite critical about the data quality of the climate databases, and particularly critical about the adjustments to the recorded temperatures that account for much (or perhaps all, it's hard to say) of the warming in the 20th century.

There is a long and detailed post at Judity Curry's blog about how the adjustments are done, and why:
Having worked with many of the scientists in question, I can say with certainty that there is no grand conspiracy to artificially warm the earth; rather, scientists are doing their best to interpret large datasets with numerous biases such as station moves, instrument changes, time of observation changes, urban heat island biases, and other so-called inhomogenities that have occurred over the last 150 years. Their methods may not be perfect, and are certainly not immune from critical analysis, but that critical analysis should start out from a position of assuming good faith and with an understanding of what exactly has been done.
So far, so good, although I'm quite sceptical about how Urban Heat Island adjustments are made.  I'd like to see these broken out separately, because recent temperatures should be adjusted downwards for UHI, which means that other adjustments (for Time Of Day, etc) would have to be significantly higher than they would appear to be.  But that's just me.

But this whole topic underlines how much better the satellite data are:
  1. It's a truly global measure because it will record temperatures over open ocean and other places you can't put a weather station.  No infilling is needed.
  2. The same instruments measure all locations, so are immune to many of the biases that weather stations are prone to.
  3. Time Of Day issues should not be a concern.
  4. Any instrumentation changes are the result of replacing a satellite and so appear globally, not in only localized data.
The problem, of course, if that satellite data (RSS and UAH) only go back to 1979, and so is mute on the magnitude and sign of the 20th century's climate change.  We do know that there's been zero warming for 17 years and 10 months, per RSS.

But my biggest problem is with the overall philosophy, summed up in this paragraph:
Diligent observers of NCDC’s temperature record have noted that many of the values change by small amounts on a daily basis. This includes not only recent temperatures but those in the distant past as well, and has created some confusion about why, exactly, the recorded temperatures in 1917 should change day-to-day. The explanation is relatively straightforward. NCDC assumes that the current set of instruments recording temperature is accurate, so any time of observation changes or PHA-adjustments are done relative to current temperatures. Because breakpoints are detected through pair-wise comparisons, new data coming in may slightly change the magnitudeof recent adjustments by providing a more comprehensive difference series between neighboring stations.
And so to the real dispute here.  I don't so much object to the data as reported as to the assumption that it is valid for a scientist to modify observational data after it was recorded.  That just feels wrong to me.  And it's what this whole ZOMG THERMAGEDDON thing is about.

And it is the most important reason that I like the satellite data.


Goober said...

My opinion on the matter is that Anthony Watts conclusively proved, with his comprehensive surveys of the siting of surface recording stations, that there is going to be a bias towards warming due to poor siting and heat island effects.

The fact that the climate scientist's adjustments are still clearly adjusting UP from the raw data means that everything they do with surface stations is suspect. From the siting issues that Mr. Watts identified, I would expect adjustments to be negative, not positive.

Dave H said...

Back when I was a lowly electronics tech one of our senior engineers explained the care and feeding of a Lab Notebook to me. Lab notebooks can become legal documents if they're called on to provide evidence of who invented what and when during patent litigation. One of the very first rules the engineer told me was write down what you see when you make a measurement or observation. If the voltmeter say 12.8, write down 12.8, even if you know the real voltage is 1,280 because you're using a 100:1 voltage divider. Write down what you see, then do any conversions, corrections, or interpretations elsewhere in the book. Then explain how you corrected it, and why.

Raw data often do need to be massaged, but an important part of being able to review and repeat experiments is to know exactly what the original data are.

Borepatch said...

Goober, yeah, I'd expect adjustments to recent data would be negative, not positive.

J Melcher said...

I would be vastly better prepared to accept the adjustments if the original data were (had been) freely and quickly provided to anybody who asked for it.

When, in particular, Phil Jones at CRU declared that unspecified "confidentiality agreements" to protect "proprietary interests" in the original data prevented him from releasing anything EXCEPT adjusted homogenized and altered data, then I have no confidence in anything else he brings forward.

Ditto Lonnie Thompson and paleo-ice data.

TripleDitto Michael Mann and his tree ring circus. (tm Mark Steyn)

That said, I am still not prepared to "infill" or interpolate data into polar regions where we have had no instruments or only the Soviet Union's "official Party" instruments for much of the 20th century. Had a tenth of the money spent on computer modeling efforts since 1998 been invested instead in on-site themometers in the polar regions, we would have EVIDENCE. As is is, for all my children's lifetimes so far we have nothing but claims and counter-claims, arguments and namecalling.

THIS is the example "scientists" set for our next generation?

kx59 said...

I don't like any of it.
Who controls the satellite data?
They both got busted recently tweaking surface temp data.

Borepatch said...

kx59, so far it seems on the up and up. To me, at least, and I've been sniffing for something "off" for a while now. Haven't found it.

Will said...

For me, the whole problem with temp records can be summarized by the photo history of one of the sensors that is STILL IN USE: First photo shows it in a field. Then buildings show up nearby. Finally, they turn the field into a blacktop parking lot that surrounds the sensor pole!

What sort of idiot thinks that the sensor has had a consistent environment during it's lifetime? They expect me to think ANY of the data is real, when that sensor's reading is still considered valid? I say they have violated normal scientific rules, and should be sacked from their positions, tarred, feathered, and horsewhipped to remove the resulting coating.