NIWA's explanation raises major new questions

The NIWA climate controversy took a new twist tonight with the release of new data from the government run climate agency.

Reeling from claims that it has massaged data to show a 150 year warming trend where there isn't one, NIWA's chief climate scientist David Wratt, an IPCC vice-chair on the 2007 AR4 report, issued a news release stating adjustments had been made to compensate for changes in sensor locations over the years.

While such an adjustment is valid, it needs to be fully explained so other scientists can test the reasonableness of the adjustment.

Wratt is refusing to release data his organisation claims to have justifying adjustments on other weather stations, meaning the science cannot be reviewed. However, he has released information relating to Wellington temperature readings, and they make for interesting reading.

Here's the rub. Up until 1927, temperatures for Wellington had been taken at Thorndon, only 3 m above sea level and an inner-city suburb. That station closed and, as I suspected in my earlier post, there is no overlap data allowing a comparison between Thorndon and Kelburn, where the gauge moved, at an altitude of 135 metres.

With no overlap of continuous temperature readings from both sites, there is no way to truly know how temperatures should be properly adjusted to compensate for the location shift. 

Wratt told Investigate earlier there was international agreement on how to make temperature adjustments, and in the news release tonight he elaborates on that:

"Thus, if one measurement station is closed (or data missing for a period), it is acceptable to replace it with another nearby site provided an adjustment is made to the average temperature difference between the sites."

Except, except, it all hinges on the quality of the reasoning that goes into making that adjustment. If it were me, I would have slung up a temperature station in the disused location again and worked out over a year the average offset between Thorndon and Kelburn. It's not perfect, after all we are talking about a switch in 1928, but it would be something. But NIWA didn't do that.

Instead, as their news release records, they simply guessed that the readings taken at Wellington Airport would be similar to Thorndon, simply because both sites are only a few metres above sea level.

Airport records temps about 0.79C above Kelburn on average, so NIWA simply said to themselves, "that'll do" and made the Airport/Kelburn offset the official offset for Thorndon/Kelburn as well, even though no comparison study of the latter scenario has ever been done.

Here's the raw data, from NIWA tonight, illustrating temp readings at their three Wellington locations since 1900:

What's interesting is that if you leave Kelburn out of the equation, Thorndon in 1910 is not far below Airport 2010. Perhaps that gave NIWA some confidence that the two locations were equivalent, but I'm betting Thorndon a hundred years ago was very different from an international airport now.

Nonetheless, NIWA took its one-size-fits all "adjustment and altered Thordon and the Airport to match Kelburn for the sake of the data on their website and for official climate purposes.

In their own words, NIWA describe their logic thus.

• Where there is an overlap in time between two records (such as Wellington Airport and Kelburn), it is a simple matter to calculate the average offset and adjust one site relative to the other.
• Wellington Airport is +0.79°C warmer than Kelburn, which matches well with measurements in many parts of the world for how rapidly temperature decreases with altitude.
•  Thorndon (closed 31 Dec 1927) has no overlap with Kelburn (opened 1 Jan 1928). For the purpose of illustration, we have applied the same offset to Thorndon as was calculated for the Airport.
• The final “adjusted” temperature curve is used to draw inferences about Wellington temperature change over the 20^th century. The records must be adjusted for the change to a different Wellington location

Now, it may be that there was a good and obvious reason to adjust Wellington temps. My question remains, however: is applying a temperature example from 15km away in a different climate zone a valid way of rearranging historical data?

And my other question to David Wratt also remains: we'd all like to see the metholdology and reasoning behind adjustments on all the other sites as well.

Comments

[Steve Netwiter]

That's an excellent explanation, thank you.

Of course, temperatures may have been rising since 1900. The real question is what were they doing over the last 2000 years?

Are they "exceptional" as the IPCC claims, or just typical of the natural variations?

I'm surprised that the scientists are not more open to having their work examined. I thought that's what science was about.

It's the prime aim to find errors, remove them, and move on?!

Steve

[Dave]

To me, it looks like the adjustments for five or six of the seven weather stations trend upwards over time, and that these upward trends in adjustments are what give the bulk of the warming trend in NIWA's official graph. Without the adjustments, the paper describes the warming trend as "statistically insignificant at 0.06°C per century since 1850."

[John Silver]

You can not move a place.
Adjustment = forgery.
Difficult to understand?

[Dave]

I'll accept the +0.79°C for the periods between 1928 and 1970, but as the Wellington graph from the Climate Science Coalition shows, other offsets are applied before 1928. After 1970, the offset appears to vary wildly.

[Dave]

In my last comment, I meant to say:

I'll accept the +0.79°C offset for the periods between 1928 and 1970, but as the Wellington graph from the Climate Science Coalition paper shows, other offsets are applied before 1928. After 1970, the offset appears to vary wildly.

[Lazarus Long]

Um, aren't airports sorta like heat sinks, considering that they consist of thousands and thousands of acres of blacktp or concrete?

And this is.....science?

[Ponsonby]

Tell Wratt that he'll have to resign in parallel when Jones of CRU goes. That should wrattle his cage.

http://www.guardian.co.uk/environment/georgemonbiot/2009/nov/25/monbiot-climate-leak-crisis-response

[Andrew]

If the airport readings were articially hot due (eg. due to the measurement station being sited near a concrete runway) then that hot bias will be transferred to all subsequent Kelburn measurements.

Nothing can be inferred from the fact that 'Airport' and 'Thorndon' altitude and readings are similar. It might have been warmer 100 year ago. If so, the adjustment they have applied would completely erase that fact.

If this is the best case they can find to defend then I worry about all the other adjustments they haven't published.

Without further tests their adjusted data simply cannot be trusted.

All these changes and offsets need to be clearly noted, explained and published so they can be independently reviewed. It is not acceptable for a politically motivated clique to make these adjustments in secret - then expect the public to trust their adjusted graphs.

[Larry]

Gee! What a coincidence. The unadjusted data shows no major trend up or down. Amazing. What are the odds to have new measurements stations have such an overall increase in temperature adjustments?

[Ponsonby]

Developments at Bishop Hill on code.

http://bishophill.squarespace.com/blog/2009/11/26/smoking-gun.html#comments

[AJ Abrams]

If NZ temp reconstruction is about the slope...then all they had to do was remove Wellington prior to 1928. A 1928 to 2009 slope would be sufficient to tell if warming was happening.

So what does it say...well that 1924 to 2009 data (unadjusted) says no warming. You simply can't argue with that. There is your unmoved, no adjusted temp reading from 1924 to 2009 (84 years) showing nothing alarming happening. Why do you need more. Look at other known stations in NZ (I have) that haven't moved and are in prime (read no UHI effect ) locations. They all say no real warming. Case closed. What you have hear is your NZ scientists manipulating data to tell you the story they believe is true, not actually the truth as can plainly be seen.

Time for you to toss out bad science, bad scientists, and the politicians that helped pull the wool over your eyes.

[Dave]

Andrew, from NIWA's graph in their explanation, the measurements from Kelburn and Airport appear to track each other well with a 0.79°C offset during the period of overlap. My concerns relating to the Wellington adjustments are
1) The graph for Wellington in the Climate Science Coalition's paper shows that the offset between the unadjusted and adjusted temperature varies wildly after 1970. Why? Presumably, data from after 1970 is from Airport, the current station location, and therefore shouldn't require adjustments relating to location change.

2) How were offsets prior to 1928 derived?

And, as others have noted, if Wellington is showing a warming trend even when adjusted correctly for location, it could be due to Urban Heat Island. I wonder how many of the other six stations are located in urban areas.

[Dave]

AJ Abrams, all seven of the stations have adjustments -- not just Wellington. NIWA picked Wellington as an example to illustrate part of their adjustment methodology.

[AJ Abrams]

Dave,

You totally missed my point. I am talking about the original RAW data from wellington after it was moved to 125 M above sea level. All you need to look at is that one set from 1925 to current. Period. Since the only adjustment that could POSSIBLY be needed for that set is for UHI, which is a downward adjustment, you can see that there is no reason for alarm. Period.

I have looked at the unadjusted data, as it's now posted on a few sites. There is nothing to see and absolutely no reason to adjust temperature upward on that station. All you have to do is toss out pre 1925 data and look at what you have left.

[George Turner]

Seperating the three curves and looking at their start and end points:

The Thorndon readings went up by 0.05 degrees.

The Kelburn readings went down by 0.4 degrees

The Airport readings went up 0.1 degrees.

So you've got +0.05 - 0.40 + 0.1 = um, I got -0.25, they got +1.25

Someone is being too clever by half.

[Dave]

AJ Abrams, yes, I misread what you were saying, but I think the unadjusted data from 1928 to present-day has to be separated into three curves like George Turner did. I think NIWA changed from Kelburn to Airport around 1970.

[Dave]

Oh, you were talking about the Kelburn data from the graph NIWA gave in its explanation, not the unadjusted data from the graph for Wellington in the Climate Science Coalition paper.

[bill]

What is the accuracy and repeatability of these stations? Is it reasonable to expect two thermometers at the same place to agree to three decimal places?

[AJ Abrams]

Bill,

The accuracy of the thermometers isn't an issue because we are looking for trends. If a thermometer reads half a degree high, it doesn't effect the trend.

[Dave]

AJ Abrams, the Kelburn and Airport curves overlap, and the Kelburn curve looks like its missing the last datapoint.

NIWA's combined Kelburn/Airport curve goes up 0.6 degrees.