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Inspired by the title to this question, is there a shift in average daily temperatures caused by the DST change in human activities?

I can picture any number of mechanisms by which a shift could happen (eg. more cars driving past the thermometer at the time the measurements are taken), so has such a shift been found?

user2821
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Mark
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  • I was tempted to title this "Are average daily temperatures affected by DST?", but I figured that would be too confusing. – Mark Mar 28 '17 at 01:37
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    I'm assuming you mean daylight savings time (DST). Also, I'm curious what mechanism you would think changes the average daily temperature. The average daily temperature would probably remain the same, but the timing of the diurnal temperature curve could possibly change due to observance of time zones. – f.thorpe Mar 28 '17 at 01:55
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    Related (but IMHO not a dupe): https://earthscience.stackexchange.com/questions/9970/are-average-daily-temperatures-affected-by-dst.

    That question asks about whether the shift to DST affects measurement methodology. This question, I think, is asking about differences in anthropological effects on temperature.

     – Semidiurnal Simon Mar 28 '17 at 10:55
  • By average daily temperatures, do you mean the mean 24-hour mean temperature, or the average temperature at a specific mean local time? – gerrit Mar 28 '17 at 11:06

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Firstly you need to define what you mean by average daily temperature. What algorithm are you going to use to compute it (from several time spaced measurements), why and what do you think the result represents.

Obviously if you use a measurement which is going to be affected by very local anthropogenic activity (e.g. cars) you can expect timing of activities to affect individual measurements. a measuring station which is going to be thus affected is not really going to be useful for anything wider or general though.

When siting weather stations we try to find locations which are not subject to such local disturbances. Ideally well away from any heat producing apparatus (e.g. fixed a/c units), heated buildings, variable traffic and so on. Locations in open non urban areas are preferable for understanding changes in the weather and climate. Past locations thus chosen however have often been compromised by the expansion of nearby housing or industry as populations and cities have expanded. This is why you sometimes see references to Urban Heat Islands (UHI) in discussions of climate measurement.

user7733
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  • Usually I'd consider it semantics, but you're right on in suggesting care with what "average daily temperature" means. To those unaware, it's still most often (high-low)/2, which indeed may come up short in terms of impacts (theoretically you could have an increase/decrease in average temp despite no energy change). I suspect Mark is more interested in any changes at all within the day. Regardless, because enough stations are urban(ish) (as you mention, UHI), I'd think it's not absolutely impossible to see such suggested changes in the overall record, though they'd likely be very very weak – JeopardyTempest May 18 '17 at 04:34