CRU Monthly Temperature is Constantly Changing

The longer I am involved in the global warming debate the more frustrated I am getting with the CRU temperature data.   This is the one of the most commonly cited sources of global temperature data, but the numbers just don’t stay put.  Each and every month the past monthly temperatures are revised.  Since I enter the data into a spreadsheet each month I am constantly seeing the shift in the data.  If it was the third significant digit it wouldn’t bother me (very much), but it is much more than that.

For example, I have two very different values for January of 2010 since September 2010.  Here are the values for January based on the date I gathered it.

Sep 10th, 2010:  January 2010 anomaly was  0.707 °C

Jan 30th, 2011:  January 2010 anomaly is now 0.675 °C

That is a 5% shift in the value for last January that has taken place in the past 4 months.  All of the initial months of the year show a fairly significant shift in temperature.

The Inconvenient Skeptic

Monthly Temperature values for global temperature change on a regular basis.

Oddly enough the yearly average seems to stay the same, but the monthly values that create the average are in constant flux.  It seems that May of 2010 is the current transition point for the year.  The latest data has the early part of 2010 as the cooler version, but past May the latest data is warmer than the earlier data.  It is very frustrating to use data that is this unstable.

It just isn’t 2010 that is in flux.  December of 2009 has undergone at least 3 significant revisions in the past 4 months.

Sep 10th, 2010:  December 2009 anomaly was  0.411 °C

November 2010:  December 2009 anomaly was 0.473 °C

Jan 30th, 2011:  December 2009 anomaly is now 0.438 °C

This constant variation in the data makes comparing temperatures even a year ago impossible.  According to the data available by the CRU, December of 2010 was somewhere between 0.151-0.213 °C cooler than 2009.  The current data indicates that 2010 was 0.178 °C cooler than 2009, but it seems likely that this will also change in the months to come.

I am going to start saving the full revision each month and will be putting together future comparisons of what should be a stable temperature set.  The changes might not seem significant, but the constant revision of global temperature data from the CRU is very concerning as it makes comparisons to past data slippery.  If I can’t trust the data from December 2009 from the CRU, how can I possibly trust data from December of 1909?

Posted in Anomaly by inconvenientskeptic on January 31st, 2011 at 12:44 am.


This post has 14 comments

  1. Richard111 Jan 31st 2011

    Brilliant work John. CRU have not issued any change notices and will deny any changes were made.

    As I type, 07:53am, in Milford Haven, Pembrokeshire, the outside temperature is -5C!!! My home is less than 100 yards from the harbour. I’ve seen surface ice late last year but none right now.
    BBC weather NEVER forecasts temps this low.

  2. Labmunkey Jan 31st 2011

    Superb work. I REALLY don’t envy you.

    This whole mess (climate science) needs auditing from the ground up. It’s embarrassing.

  3. Alexander K Jan 31st 2011

    Excellent post!
    Like Richard111 (above) I am puzzled as to why the temps on my max/min thermometer in my London backyard rarely acheives the giddy heights promised by the Met Office and promulgated by the BBC website. My yard only has vegetation in pots, no grass whatsoever, therefore should be a model urban heat island! Our forecast in TW7 are as for Heathrow but some distance from the airport and always warmer than Metropolitan London – surely that should not be so!
    Yesterday, for example, our temp was forecast to soar to+5C but +.5C was as max.

  4. John – out of interest,have you asked the CRU for any kind of explanation?

  5. There is a little reported school of AGW skepticism that keeps on pointing out that it makes no sense to construct a global average temperature by averaging individual temperatures over the earth’s surface because:

    1) A thermodynamically intensive quantity like temperature or density (as opposed to extensive quantities like mass, heat, etc.) should not be treated this way, and

    2)The fractal nature of the earth’s surface means that averaging anything over that surface will give different answers based on how far apart your measurements are taken — and the answers will not converge to a single “correct” answer the closer together you make them.

    Maybe this is the reason mathematically reasonable changes in how you average the data keep leading to annoyingly large changes in the answer you get. In short, these theoretical objections to the idea of a global average temperature may mean that, when you try to calculate it, what you get in practice is a weird sort of random-number generator. Each attempt to “improve” your estimate of the global average temperature for a given month, year, etc., will not converge to the correct value but just produce another random number within the random-number generator’s effective range, no more and no less meaningful than the previous one.

  6. Great idea to keep a public database of the changes

  7. Green Sand Jan 31st 2011

    Good work sir, please keep at it.

    I have been trying to reconcile the HadCRUT3 2010 annual anomaly.

    CRU show 2010 HadCrut3 anomaly at +0.475C

    The Met Office say 2010 HadCRUT3 +0.50C

    Whilst on the Met Office page below, the annual data shows +0.498C but the monthly data adds up to +0.475C?

    I suppose there is a perfectly simple explanation, including me getting it wrong?

  8. How will you ever been able to trust data from organisations (CRU, GISS, etc) run by unscrupulous climate politicians attempting to achieve an economic policy outcome on behalf of the UN – regulation of human CO2 output – regardless of its impact on climate?

  9. T.G.Watkins Jan 31st 2011

    To echo Richard and Alexander the BBC forecasts are unreliable. Like Richard I live in Wales but about 90miles due west and 7 miles from the coast. My outside, close to house, thermometer read -5 overnight, -3 at 9am and did not rise above 0c all day, yet the forecast for our area was +2-4c.
    Interestingly, or maybe not, I live 3 miles from an official Met Office station at RAF St. Athan. Their current real time temp. is +2, mine is 0c and I still have solid ice in my outdoor saucer which hasn’t changed all day. Sorry, theirs is +3 mine is 0.

  10. intrepid_wanders Jan 31st 2011

    Two words John, “variance adjusted” (CRUTEM3v). The more descriptive word that is missing is “recursively”.

    I am so thoroughly tired of the concept of “anomaly”. Too few under-qualified metrologist tamper with these “baseline periods” and “tweak” the data at the same time (forwards and back). None of the data is usable in any stretch of the imagination. It is only insanity.

    Ice core bubbles might be more enlightening and less frustrating 😉

  11. I am forever amazed at the money thrown at climate science – at last count something like 10.6 million dollars a day by the US gubmnt but we can’t seem to keep the thermometers straight. If this global warming is the greatest threat to humanity (outside of rap music – sorry got to get some levity in here…) then why isn’t a greater priority by thw UN or US or EU or name your bloc set on at least getting a decent, consistent measurement? (Rhetorical question I realize).

  12. old44 Feb 4th 2011

    intrepid_wanders: Do you mind, I am a Metrologist and we pride ourselves on the accuracy of our work, so don’t lump us together with the charlatan Meteorologists who adjust the data and fiddle with the programs to fit the theory.

  13. Mr. Expert,

    Are you going to have a follow up post or article about this anytime soon? 🙂


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