Data Watch: UAH Global Mean Temperature May 2013 Release

The University of Alabama-Huntsville (UAH) global average lower tropospheric temperature anomaly for May 2013 was released via the web site of Dr Roy Spencer (one of the founders of the programme that produces this temperature time series) on June 4th. The anomaly refers to the difference between the current temperature reading and the average reading for the period 1981 to 2010.

May 2013: Anomaly +0.07 degrees Celsius

This is the 13th warmest May temperature recorded since the satellite record was started in December 1978 (34 May observations). The warmest May to date over this period was May 1998 (1998 being the super El Niño year), with an anomaly of +0.58 degrees Celsius.

As background, five major global temperature time series are collated: three land-based and two satellite-based. The most high profile satellite-based series is put together by UAH and covers the period from December 1978 to the present. Like all these time series, the data is presented as an anomaly (difference) from the average, with the average in this case being the 30-year period from 1981 to 2010.

The official link to the data at UAH can be found here, but most months we get a sneak preview of the release via the climatologist Dr Roy Spencer at his blog.

Spencer, and his colleague John Christy at UAH, are noted climate skeptics. They are also highly qualified climate scientists, who believe that natural climate variability accounts for most of recent warming. If they are correct, then we should see some flattening or even reversal of the upward trend within the UAH temperature time series. To date, we haven’t (click for larger image):

UAH Temp May 2013 jpeg

One of the initial reasons for publicising this satellite-based data series was due to concerns over the accuracy of terrestrial-based measurements (worries over the urban heat island effect and other factors). The satellite data series have now been going long enough to compare the output directly with the surface-based measurements. All the time series are now accepted as telling the same story (for a fuller mathematical treatment of this, see Tamino’s post at the Open Mind blog here). Note that the anomalies produced by different organisations are not directly comparable since they have different base periods. Accordingly, to compare them directly, you need to normalise each one by adjusting them to a common base period.

6 responses to “Data Watch: UAH Global Mean Temperature May 2013 Release

  1. It looks to me like not much has happened over the past 15 years. It looks like a temperature increase of about 0.4 degC over 34 years – not something you’d notice. It certainly doesn’t match the computer model predictions over the past few years.

    I think it’s time the climate scientists went back to the drawing board – hint, have a look at cloud density and area.

    • I am not sure what your point is? Is it a) that the warming as shown by the UAH data is within normal variance or b) the trend is for a rise in global mean temperature of just over 0.1 degree Celsius per decade? Further, do you have a view over how the UAH anomaly will move in the future? Do you have conviction over that view?

  2. My main point is that the satellite data (and reasonably well supported by land data) is very different to the predictions of the computer models in the IPCC reports. If CO2 is such a strong driver, why has the temperature increase stalled? It surely shows that CO2 is not as powerful a driver as the hypothesis assumed. The scientists are desperately trying to explain this, and coming up with all sorts of wild theories. They all ignore the KISS principal – the simplest one is that CO2 isn’t the strong driver they expected.They don’t dare mention this one – might effect their research funding.

    As for the future of the UAH anomaly, it’s like tossing a coin. It could go up, down, or stay stagnant. I have no good logical reason to predict any direction. My gut feel based on solar activity, cloud formation theory (which has been neglected due to poor understanding), and coin tossing is for a longer period without significant warming..

    • So for a future average UAH anomaly over some time period, you are saying your best estimate is that it will be the same as the current average anomaly, with an equal chance that it will be higher or lower. In other words, there is no trend. In contrast, the consensus scientific view is that a trend does exist; i.e., their best estimate of the future average UAH anomaly is higher than the current average anomaly. This is putting your position in probabilistic terms. I am correct in my understanding? Further, do you have high conviction that you are correct and the scientific consensus is wrong?

  3. I have no conviction that I am right. As I said, there’s no real evidence to allow a prediction either up or down.

    I’m surprised that you bring up “consensus”. There is not a scientific consensus that increased anthropogenic CO2 emissions will result in catastrophic warming. Most scientists acknowledge that theory suggests that increased CO2 could result in minor warming. However, it’s the hypothesis that positive feedback (eg increased water vapour – the strongest greenhouse gas) will dominate negative feedback (eg cloud density and area) that’s unsubstantiated.

    Science isn’t about consensus. Science is about developing an hypothesis, and testing it against real data. If it doesn’t fit, change the hypothesis. In the case of the global warming hypothesis, they tried changing the data (eg Hadcrut, GISS).

    Years ago, medical consensus dictated that patients be bled to cure most ailments. We now know better.

    • If you think that the future will look like the present, that indeed is a prediction (indeed in financial markets, it is the starting point for any analysis).

      However, you also seem to be saying that you have no conviction that your best estimate of the future will be the same as the present. I don’t think you understand the difference. One can have strong conviction that we don’t know anything about the future or one can have no conviction that we don’t know anything about the future. These are two very different statements. The latter statement can be paraphrased as “I don’t know anything”. If so, why bother commenting?

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