What happened September 2nd? A registrar’s climate mystery
Part 1

I received a call from our conservation trainee. She was in the process of analyzing the climate from one of our offsite storage areas for 2013 and discovered something really, really odd. She sent me the data and asked if I could make sense of what happened on September 2 and 3 in the said year. Please see the graph below, showing the temperature in degrees Celsius (red line) and relative humidity in percentage (blue line) between September 2, 7 a.m. and noon on September 3. Can you make sense of what you see?


The data logger is a portable digital logger powered by batteries in the middle of a large storage area without HVAC that is approximately 2,000 square meters (about 21,500 square feet) and 5 meters (16.4 feet) high. In the next part we will discuss the graph and I will tell you the hint from a colleague that finally brought the solution.

What do you think happened in those 29 hours?

A Hint
The Solution

Full spreadsheet of data

This post is also available in Russian translated by Helena Tomashevskaya.


12 thoughts on “What happened September 2nd? A registrar’s climate mystery
Part 1”

  1. I would suggest that the logger was actually removed from it’s original location. The changes in humidity are being driven by the changes in temperature. Looking at the conditions before and after the fluctuations the conditions are fairly stable. The sudden change in temperature could be caused by someone accidentally putting the logger into their bag that has come from a warmer environment, walked out of the building allowing the temperature to cool, then got in a car,driven home with the air con on, got home at about 17:30, the car is left in the evening sunlight allowing the car to warm up before the sun disappears giving a gradual cool down overnight. At 07:30 next morning, the person drives into work, realises they have taken the logger home and puts it back in situ.

  2. There was marked solar flare activity from Sept 1 to Spet3 2013. Could that have had anything to do with disrupting the datalogger readings?

  3. I agree with Kathy Karkut, something has fallen over the datalogger unit creating a microclimate – a sheet of bubble wrap or tissue – or some creature has interfered with the sensor – or maybe there is a ghost in the machine…

  4. A staff member did something dry as they left for home and undid it when they arrived in the morning;not sure what they did though!

  5. My first avenue of inquiry would be to confirm the integrity of the datalogger; was the data compromised in its collection, interpretation, storage or transmission?

    Secondly, was there any other evidence of the T and RH fluctuation?

    Thirdly, what are the items in storage? Could anything there be a cause?

    Perhaps there would be clues in those answers.

  6. Potentially something was dropped over the data logger such as a box or bubble pack, etc. and the readings are for a very small contained space surrounding the DL. The next time someone was near the DL they removed the covering.

  7. I would think someone took the datalogger to another room (warmer, dryer) and then maybe outside in the car for a night, to put it back the 3th september…?

    Geert Bellens

  8. Angela,

    If someone was breathing close to the logger, the temperature would rise at 16u30, but humidity also.

    If a heat source was involved (local heater, lamp,..) I would expect rising temperatures, and lower humidity, but no that drastically.

  9. The weather was mild during early September 2013, with daytime temperature at around 24 deg C. However, yourT changes are too rapid to be caused by normal daily fluctuations. The RH changes in this case are counter correlated with your T changes, which suggests that something affected T but confirms you have no independent RH control. As you say there is no HVAC an equipment malfunction can be excluded. Something lead to the steady then rapid T increase, then slow drop during thenight, followed by rapid normalisation of conditions. Do you have central heating in the building which came on, the store got too warm, someone opened a window in the evening of the 2nd which was left open over night then closed in the morning of the 3rd?

    1. Your considerations regarding the daytime temperature are correct, as you can see by the weather dates of the nearby weather station: http://archiv.mannheim-wetter.info/2013/pcws/20130902.gif
      The steady increase until about 16:30 is pretty normal, regarding the outside temperatures and the nearly not insulated storage, nothing to be proud of, but nothing to be particularily concerned about.
      I like your idea with the central heating gone mad, we have one but it wasn’t turned on because of the rather mild temperatures. And no, no one opened a window to regulate the temperature.

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