This new paper by Dr. Ross McKitrick of the University of Guelph is a comprehensive review of the GHCN surface and sea temperature data set. Unlike many papers (such as the phytoplankton paper in Nature, complete code is made available right from the start, and the data is freely available.
There is a lot here that goes hand in hand with what we have been saying on WUWT and other climate science blogs for months, and this is just a preview of the entire paper.This graph below caught my eye, because it tells one part of the GHCN the story well.
1.2.3. Growing bias toward lower latitudes
The decline in sample has not been spatially uniform. GHCN has progressively lost more and more high latitude sites (e.g. towards the poles) in favour of lower-latitude sites. Other things being equal, this implies less and less data are drawn from remote, cold regions and more from inhabited, warmer regions. As shown in Figure 1-7, mean laititude declined as more stations were added during the 20th century.
Here’s another interesting paragraph:
2.4. Conclusion re. dependence on GHCN
All three major gridded global temperature anomaly products rely exclusively or nearly exclusively on the GHCN archive. Several conclusions follow.
- They are not independent as regards their input data.
- Only if their data processing methods are fundamentally independent can the three series be considered to have any independence at all. Section 4 will show that the data processing methods do not appear to change the end results by much, given the input data.
- Problems with GHCN, such as sampling discontinuities and contamination from urbanization and other forms of land use change, will therefore affect CRU, GISS, and NOAA. Decreasing quality of GHCN data over time implies decreasing quality of CRU, GISS and NOAA data products, and increased reliance on estimated adjustments to rectify climate observations.
From the summary: The quality of data over land, namely the raw temperature data in GHCN, depends on the validity of adjustments for known problems due to urbanization and land-use change. The adequacy of these adjustments has been tested in three different ways, with two of the three finding evidence that they do not suffice to remove warming biases.
The overall conclusion of this report is that there are serious quality problems in the surface temperature data sets that call into question whether the global temperature history, especially over land, can be considered both continuous and precise. Users should be aware of these limitations, especially in policy sensitive applications.
Read the entire preview paper here (PDF), it is well worth your time.
h/t to E.M. Smith
Put the high one in
And you take the low one out.
What’s it all about?
===============
David, UK (August 3, 2010 at 4:56 am) “the new iconic image of climate science is not the Hockey Stick – but the Chimney Brush.”
LOL – I love it. That has really made my day!
Sounds like this paper should be sent to every member of Congress, with a letter explaining its implications: forget about AGW—there isn’t any.
No point in sending to the White House.
/Mr Lynn
OT, Solar Magnetic Burst
I wonder if these may be normal part of longer term solar cycles which are related to volcanic activity.
How about an animation that shows station location changes? And one that shows regional weighting changes?
Thank you Ross and Anthony.
This is why they don’t freely allow people to look at the code and data. I’ve been saying for ages that this is the real man-made global warming. :o)
I wonder if their instruments are calibrated, and if they are what is the traceability of their calibrating standards and procedures. And how are their instruments maintained. As Jagger says there is no systematic requirement for uniformity In data collection in terms of locations and conditions.
I wish someone would explain why “adjustments for known problems due to urbanization and land-use change” are made to the raw data from a station. If the point of the exercise is to measure the temperature at a given spot, then why would one change the values based on the above parameters? The temperature there is the temperature there — period. If it gets warmer because of increased urbanization, well then, it gets warmer. Are they trying to make the numbers look like what they might be if nothing had changed?
I can see making adjustments if the instruments are changed and the new one reads half a degree higher than the old one. I can see moving the site if a new asphalt interstate is built 100 feet away. But if a site gets moved, then that data point should be terminated and a new one instituted. What they’re trying to do is to make the data appear as though there is an uninterrupted series of measurements at each location, and that means changing the data with a SWAG fudge factor.
I wonder what these graphs would look like if only the raw data were used? When I look at the raw data for site in out-of-the-way places in West Virginia, or other places that haven’t seen any major development over the years, there is no AGW signature visible in those records. What’s being done to the raw data for the sake of “accuracy” is a crime against data.
Please help me!!
Didn’t the World spent billions of dollars on new weather satellites in the last decade.
1) Wasn’t one of the purposes of the satellites to measure land and sea temperatures????
2) If those temperature are accurate, why do we need ground (water) based stations???
3) Where are the satellite temperature records?? Are there any??? Who keeps them??
4) If we are so advanced in measurement technology, why don’t we have “complete” global temperature records via space???
WUWT????
Re: airport v rural stations
There is much criticism of the use of weather stations at airports. Is there actually any evidence that the temperature trends at airport stations are signiicantly greeater than the trend at nearby rural stations. I’m sure there must be some that are, but equally I’ve noticed some that quite definitley aren’t.
Excellent summary. Now it is time that someone will try to fix the mess and recalculate everything all over.
RE:
John Finn says:
August 3, 2010 at 6:36 am
“greeater” should be “greater” and “definitley” should be “definitely”
Verity Jones says: August 3, 2010 at 3:41 am
“What Ross McKittrick is showing – that the adjustments tend to cool the older records and warm the more recent analysis is something I have seen too but wondered how widespread it was. Now we know.”
But what isn’t said is who uses the adjusted GHCN data. Not GISS, not CRU. I believe NCDC does. But Zeke showed that a reconstruction using the adjusted file gave very similar results to the GHCN unadjusted.
kim says:
August 3, 2010 at 5:11 am
“Put the high one in
And you take the low one out.
What’s it all about?”
===============
That’s called jiggery-pokey not the hokey-pokey. That’s what it’s all about.
What is of interest here is temperature trend, not absolute temperature. If you look at latitudinal effect on temperature, you see this:
Temperature trend land & ocean.
This figure shows the well-known increase in temperature trend (land only) with increasing latitude. Decreasing the mean latitude of the stations over time has the paradoxical effect of decreasing the net global warming over that period.
The magnitude of this latitudinal effect is significantly reduced or even removed if one does a more careful “area weighted” average. In that case, you have to look at how the particular analysis performs its area weighting. The only one I’ve looked at in any detail is CRUTEMP, for which there is still a residual bias in latitude even after gridding:
CRUTEMPmean latitude
Again this has the effect of understating early 20th century warming compared to late 20th century warming. However even the IPCC admits that prior to circa-1980, anthropogenic activity played little role in global warming.
So again, somewhat surprisingly, this latitudinal bias has the effect of deemphasizing the period of natural warming in comparison to the one for which it is thought (in the mainstream climate community at least) that anthropogenic activity played a large role.
In the past accurate measurement of important variables like time, length, mass and temperature occupied the thoughts of the greatest minds of the age. They were attracted by the knowledge that accurate measurement was fundamental to science and engineering and their whole future way of life. Accuracy still is still fundamental to science but it is not fundamental to business and politics. In fact it tends to get in the way of policy. Scientists are now paid to get results and the results are defined by companies and politicians. Truth and accuracy are no longer where the money is.
For example the quality of automotive science thoughout the world is astounding as are the scientists involved but would you expect a scientist from GM to say that Honda made a better car even if he knew that to be true. He is effectively paid to lie. I would even guess that most people would find that reasonable given that his continued employment would be at risk if he told the truth. And yet the general public find it hard to believe that climate scientists would lie about a political “vehicle” which they are being paid to engineer.
I think the reality is that 30 to 40 years ago when the current cabal of IPCC climate scientists started their careers it was a cinderella science which attracted mainly third rate minds (relative to the big money fields like finance and biosciences and the big prestiege fields such as high energy physics). They have often done third rate jobs and are trying to hide their mistakes with second rate subtifuge and first class marketing. It is a sad time for science.
There is good climate research going on now and I have read some really well written papers. However this research tends to be very specific and not to extrapolate from random noise to future catastrophy so never makes it into the news. Doing good research is not sexy so funding dries up. And then a well funded project comes along, no questions asked…. a man’s got to live!
Very useful video, except the first hundred years or so is like watching paint dry. However the video from 1985 on shows much more clearly for the mathematically innumerate the point of McKitrick’s graph.
aaron says: August 3, 2010 at 5:48 am
“How about an animation that shows station location changes?”
If you mean station distribution, Ron Broberg has it.
John Finn says: August 3, 2010 at 6:36 am
Re: airport v rural stations
There is much criticism of the use of weather stations at airports. Is there actually any evidence that the temperature trends at airport stations are signiicantly greeater than the trend at nearby rural stations.
Zeke looked at this in detail, and found that a reconstruction using airports vs non-airports gave very similar results. I looked less thoroughly, but found the same.
Peter Shroud says at 4:09 “On page 11 we see the percentage GHCN stations located at airports from 1890 – 2009. But according to WikiAnswers the first airport was built in 1909, College Park Maryland.”
Those figures are taken from an analysis at http://chiefio.wordpress.com/2009/12/08/ncdc-ghcn-airports-by-year-by-latitude/ The author, E. M. Smith, says there:
“This is a bit hobbled by the primitive data structure of the “station inventory” file. It only stores an “Airstation” flag for the current state. Because of this, any given location that was an open field in 1890 but became an airport in 1970 will show up as an airport in 1890. Basically, any trend to “more airports” is understated. Many of the early “airports” are likely old military army fields that eventually got an airport added in later years.
With that caveat, the charts are rather interesting. ”
The important point is not the absolute percentage of airports, but the warming imputed because the percentage has changed.
JamesS says: August 3, 2010 at 6:27 am
“I wish someone would explain why “adjustments for known problems due to urbanization and land-use change” are made to the raw data from a station. If the point of the exercise is to measure the temperature at a given spot, then why would one change the values based on the above parameters?”
GHCN publishes unadjusted figures, and that’s what the main indices use (though they may themselves adjust). But you’re right – adjusted figures do not give a better result for a particular location. The thing is, when you use temperatures to compile a global estimate, then the station temp is taken to be representative of an area (or more correctly, its anomaly is representative). So the corrections are to respond to known issues which would make it less representative.
Page 13 of the McKitrick report.
I believe most people here understand what you say, but the point is also that larger portions of the Earth, especially those considered to be most important to the detection of warming, are doing with fewer actual measurements. This does make the results more dependent on errors in measurement and adjustment, wouldn’t you say?
I suspect that all scientists, good and bad, consider themselves to be experts at using computers to analyse data. I also suspect that this is seldom the case. Thus, all scientific papers that rely extensively on computers to manipulate and interpret data should have the analysis reviewed by professional computer experts, such as Professor Ross McKitrick, not by other scientists.