UAH Global Temperature Update for September, 2012: +?.?? deg. C

October 4th, 2012 by Roy W. Spencer, Ph. D.

I’ve been receiving an increasing number of e-mails asking, basically, is there something wrong with the Aqua satellite daily global temperatures which are posted at the NASA Discover website?

Well, John Christy and I are ready to say, “yes, there is”.

Over the last few years, the NASA Aqua satellite has been our “backbone”, or reference, satellite since it is kept in a stable orbit with on-board propulsion. This means there are no orbital decay adjustments or diurnal drift adjustments necessary for the AMSU measurements made from Aqua.

Because of this advantage Aqua has over the NOAA polar orbiters, the other satellites (NOAA-15 and NOAA-18) are basically forced to agree with the temperature trends from Aqua AMSU in our processing.

Unfortunately, it just so happens that the main channel we use for tropospheric temperature monitoring, AMSU channel 5, has been experiencing increasing noise in recent years on the Aqua satellite. Evidence of this can be seen in the following plot from those 3 satellites (NOAA-15, NOAA-18, and Aqua) over the last 3 years (click for large version):

The numbers plotted are the average absolute differences from each AMSU scan line to the next in our lower tropospheric temperature (LT) retrieval. With a scan line separation of about 50 km, even a noiseless instrument would produce non-zero values because the satellite is always passing over the tropics, then the poles, then the tropics, etc. In other words, the above plot contains both signal and noise.

Obviously, the noise in Aqua AMSU channel 5 has increased dramatically. In fact, the NASA AIRS Team stopped using Aqua AMSU ch. 5 in their temperature retrievals months ago. (BTW, the LT computation causes an amplification of the instrument measurement noise, but the relative increase in Aqua noise vs. the other satellites is not affected, which from the above plot looks like about a factor of 7 or 8).

So, you might ask, why include Aqua AMSU in our processing if the noise is so large? Well, because we use over 300,000 measurements to get a global monthly average. If the noise in Aqua AMSU ch. 5 was truly random, the huge increase in noise seen in the above plot should not cause a drift in the calibration of the instrument.

But increasing noise in a microwave radiometer can have different causes. And not all of the causes would result in truly random noise characteristics. That appears to be the case with Aqua AMSU ch 5.

So What Is the Corrected Temperature Anomaly for September, 2012?

Version 6.0 of our dataset will take care of the diurnal drift effects, but due to our other responsibilities, John and I have not quite finished v6.0. Nevertheless, we think we can we produce a preliminary update in the next couple weeks. The results suggest that there has been a spurious warming in Aqua AMSU LT which has reached close to 0.2 deg. C last month. It has been increasing over the last couple years. Do NOT expect the long term warming trend during 1979-2012 to decrease, though, because there are other changes to the long-term time series which cancels out the recent spurious warming.


26 Responses to “UAH Global Temperature Update for September, 2012: +?.?? deg. C”

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  1. How do we suppose to feel confident in data we receive?

    It seems like all the data no matter the source always has some problem associated with it.

    The best most reliable data maybe will be the new thermometer placements recently installed across the nation.

    For my money thermometers placed in the correct setting would yeild the most reliable accurate temp. data.

    Without the risk of high tech. problems.

    • There are no perfect data. The USCRN sites are probably the closest we have to perfect, but it’s only a few years and only over a tiny fraction of the Earth.

      Nevertheless, for the U.S. going forward, I think USCRN is what U.S. surface temperatures should be anchored to.

  2. Bubba says:

    Now i think that the so called “satellite temperature record” is piece of… No matter that is UAH, RSS or something else.

  3. Ray says:

    In my experience, recent (approx 1-2 years), UAH anomalies have been up to 0.1c higher than would be exected from the equivalent AQUA CH5 anomaly. I am not sure how the above would explain that.
    Also, surely if there have been “other changes in the long-term time series which cancels out the recent spurious warming”, if that “spurious warming” is removed, the trend would be lower?
    Unless, of course, those other changes are also spurious.

  4. Drew says:

    This dataset is starting to have some consistancy issues that will make several folks question the methods. Thank you Dr. Spencer for being upfront with this issue. Most importantly, I hope that you will be transparent with the adjustments that you are making from the data. Why is the issue brought to our attention now after what appears to be one of the warmest Septembers? Why not earlier?

  5. That was what I was thinking of in my earlier post.The USCRN

    I would also like if possible Dr. Spencer ,if you could post a graph or chart which would show the average albedo for the earth on a monthly basis. Is such a product available?

    If not it needs to be.

  6. Daniel Reppion says:

    Given that an averaging of the difference between sep ’11 anomalies and sep ’12 anomalies gives a figure of roughly .43C; can we anticipate the true value to be about .25C ish, assuming the .2 error?

  7. JJ says:

    Are these issues only relevant to the longer term calculations of trend, or are they also responsible for the seemingly erroneous warm TLT temp departure over the past couple of weeks?

    According to the trace on the Discovery web page, temps have been rising when they typically are falling fast – leading to the circumstance where we currently sit at record high temps for the period …

    • Daniel Reppion says:

      Do you mean they are falling fast because of the NH autumn, or that anomalies are lower than normal?

  8. oliv says:

    Maybe you could just show a polynomial fit to entertain us ?

  9. Chris says:

    How come global sst anomalys for 2012 vs 2010 show 2012 .1 to .15C above 2010 by Oct 1st?

    But now the anticipated 2012 vault above 2010 isn’t real, this is not adding up? You take me for a fool Doctor?

    Let’s see:

    2010 already plummeted into la nina, even with a lag temps would easily reflect cooling vs 2012 when 2012 has global sst’s that much higher.

    solar indices say 2012 has increased TSI vs 2010 at this time.

    The PDO and AMO are not relevant since global sst supersede them.

    I can’t imagine how 2012 has less polar sea ice during the height of the polar warming amplification.

    Ncep reanalysis shows the warming of 2012 vs 2010

    and obviously global sst anomaly’s support 2012 being warmer than 2010 at this point.

    This doesn’t add up.

  10. Jenn says:

    It appears the noise has actually gone down in September according to your graph. Why adjust September down .2 degrees and not the whole recent dataset? NCDC analysis does show record warmth the last 2 weeks, so it appears amsu is at least picking up on a trend.

  11. sillyfilly says:

    Dr Spencer,
    The recent AMSU Ch 5 data, particularly for October,
    shows a strong warming pattern. Is it this pattern that alerted you the problem? Or was this problem already identified, and if so, why not rectified earlier? And how have you quantified the variance in temps to -0.2dc?

  12. Chris says:

    http://i174.photobucket.com/albums/w109/frivolousz21/compday-195.gif

    NCEP/NCAR need’s to get the spurious warming under control.

  13. Ian says:

    This must be a joke. Or else it is a case of:
    He who lives by the sword (making a song and dance on apparent cooling trends in the UAH data) dies by the sword (when the data refuse to cooperate).

  14. Stephen Wilde says:

    This means that for every measurement system we have the so called ‘changes’ in global temperature are well within the error margin.

    The surface sensors are affected by UHI plus speculative and thus challengeable ‘adjustments’ whereas the satellite figures are affected by a variety of confounding factors that may or may not have been accurately unravelled (most likely not).

    All we are left with is the simple observation that the climate zones have shifted a bit and the SSTs rise and fall from place to place over time.

    We have no real idea whether global temperatures have risen or fallen significantly at all as opposed to the available energy having just been redistributed over time with no measurable effect on Earth system energy content.

    Is that enough to support policy decisions of any description ?

  15. Ansgar John Brenninkmeijer says:

    It is a pity that the problem is that it is showing too high temperatures. If the deviation were to the cold side and you correctrf the temperstures up, that would have made your work seem more objective.

  16. Ray says:

    Jenn says:
    “It appears the noise has actually gone down in September according to your graph.”
    I am not sure how do you come to that conclusion.
    Surely the graph shows noise at an all time high?
    Or am I missing something?

    • Jenn says:

      I meant the trend line. The noise is not rising as fast as it had before. Meaning this action seems a bit late.

  17. Daniel Reppion says:

    I have to say – down here in South-East Australia, in early-mid September we were having max daily in the 10 – 12C type , typical late winter early spring temperatures. Over the last weeks of the month up until now there was a noticeable increase to the mid 20s, a jump of 10 to 15C. The last few days have been up to 27C where I am (Canberra).

    Obviously this isn’t unusual, we’re coming into summer. But noisy or otherwise, the AMSU data trend is certainly consistent with my neck of the woods. Obviously that comes with caveat, local weather isn’t global temperature.

  18. Chris says:

    @Ansgar John Brenninkmeijer

    Given how warm global sst’s are.

    Dr. Spencer and his friends say move August from .34 down to .23 would be saying the TLT layer is colder than the ocean ssts which are actually probably under-done themselves because of poor high latitude sampling.

    So in the face of land based near record warmth his data set will seem next to impossible to be correct with snow and ice albedo near all time lows in September and GHGs at all time highs.

    I have a feeling this isn’t going to go unchecked like the last few have.

  19. Stephen Richards says:

    This is a great shame. Wedesperately need a temperature dataset that is both reliable and accurate without the need to manipulate the results. I thought the satelites would be able to do that but they have failed miserably.

    Perhaps NASA is both useless at climate monitoring as well as satelite control and reliability.

  20. amsu a data that is correct I hope.

  21. anthony beevor says:

    So the NASA scientists have given up on this source of data.
    It is their experiment. Have Christie and Spencer been in discussion with them? What do they say?

    I would show the results with and without inclusion of the suspect data and say “This is how it is”.

    If a vital, remote instrument ages, and becomes definitely
    unreliable , that is the end of the experiment.

  22. Tom Waeghe says:

    It wouldn’t surprise me if NASA turned off the temperature measuring satellites, especially if they show the wrong kind of trend that the current administration and U.N. want to have to support man-made global warming.