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CET Temperature Trends In April

April 18, 2016
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By Paul Homewood


Continuing on from my earlier post on CET temperature trends.

If we look at seasonal trends, we find that the largest increases in maximum temperatures have come in spring and autumn. Much smaller ones have occurred in summer, and winter trends have changed little at all.








If we concentrate on spring, we have already seen how temperatures have risen in March in recent years. We find a similar rise in April, but curiously no long term trend in May.







Looking at April more closely, we can do the same analysis as we did with March.


If we look at the number of days each year with maximum temperatures over 16C, we find that little has changed in the last couple of decades compared to earlier ones, with the exception of 2007.




However, as with the March analysis, there has been a marked decline in the number of really cold days. Both analyses equate approximately to 10th percentiles.




Again, as with March, this conclusion is supported by analysis of the hottest and coldest days.

The hottest April day by far was in 2003, but apart from that there is no indication that temperatures at the top end are either rising or becoming more common.




This is all in stark contrast to the coldest days.





We can therefore conclude that the recent rising trend in April temperatures is largely due to the absence of cold days, rather than a general rise in the average of all days or days becoming hotter.


Does any of this matter? I would argue yes.

1) I think most people would agree that fewer cold days in spring is a good thing, certainly in Britain.

2) It means that temperature extremes are becoming less, which again is surely a good thing.

3) If temperatures are not increasing at the top of the range, while there are fewer really cold days, this would suggest that the scope for further rises in spring temperatures is small. And, indeed, the trend shown on the Met Office graph above clearly shows that the trend stopped rising about a decade ago.

4) Whatever the cause of this phenomenon, it does not seem to be consistent with the greenhouse gas theory, which logically would see a gradual temperature rise across the whole range of days.

  1. Joe Public permalink
    April 18, 2016 1:22 pm

    I’ve a sneaking suspicion where April 2016 will end up!

  2. Adrian permalink
    April 18, 2016 1:32 pm


  3. April 18, 2016 1:55 pm

    Hope that you are having above average holiday weather.

    If one accepts that global temperatures are increasing by about 1 degree per century (for about the last two centuries anyway since the last LIA), are we actually missing-out?

    The global warmists will now claim that climate is less cool, i.e warmer. We are regularly told that everything is consistent with the computer model predictions!

  4. April 18, 2016 2:47 pm

    it may interest you to know that the surface temperature time series contains persistence, a property indicated by its Hurst exponent.

    • April 18, 2016 3:15 pm

      This looks fascinating, but is far beyond my stats level. I read that the temperature may be increasing at rates between 3 and 11 degK/century on different graphs. Then, using different numbers of days, that it is not altering. It also states that 20 years is not long enough to establish trends: the hiatus deniers would like that!

      Does persistence mean relationship with?

      Hope that you can simplify a bit for people like me who do not know what Hurst values are etc.

  5. April 18, 2016 3:22 pm

    Your finding is consistent with a study I did using 25 long-service stations (all European and also referencing CET):

    The warming is occurring mostly in the coldest months.
    In fact, the months of May through September warmed at an average rate of 0.17C/Century, while October through April increased at an average rate of 0.58C/Century, more than 3 times higher. This suggests that the climate is not getting hotter, it has become less cold. That is, the pattern suggests milder winters, earlier springs and later autumns, rather than hotter summers.

  6. Broadlands permalink
    April 18, 2016 3:25 pm

    In the contiguous US 48 states the warmest April “on record” was in 2006. Since then the trend has been toward cooler Aprils.

  7. Herman Aven permalink
    April 18, 2016 4:09 pm

    > “the greenhouse gas theory, which logically would see a gradual temperature rise across the whole range of days.”

    Not sure if that’s “logical”. Radiative forcing is normally defined as “altering the balance of incoming and outgoing energy”. That this extra energy would sit like some seasonal blanket around the surface or troposphere would be rather unlikely and it’s indeed not measurable as such during the last 15-20 years. For this reason the term “global warming” has been replaced by “climate change” in many publications. Some have theorized the energy will accumulate in the climate system as a whole, changing the balance. There’s no described mechanism to my knowing which defines that some gradual effect on surface temperature highs should be there in each and every season. There are just too many feedback mechanisms for that.

  8. john cooknell permalink
    April 18, 2016 8:03 pm

    Recorded sunshine hours correlate well with recorded Temps, i.e increasing bright sunshine increasing temperature, as you have stated many times.

    So surely this is explained by the absence of fog and pollution, due to the Clean Air Act. I cannot re-call any “fog day” in recent years but in my childhood “fog days” were common in Autumn, Winter and Spring.

  9. April 19, 2016 10:35 am

    TIP : #1 Renewables push forces COAL to close.
    #2 Renewables push forces COAL to NOT close, but to stay warm to be ready to provide “black start if another part of the grid fails ..adding £15m+ approx to customers bills
    Telegraph : Costs of blackout emergency plan soar as coal plants paid to keep warm

    The + is cos “National Grid has since awarded new black start contracts to more coal plants: Drax; and SSE’s Fiddler’s Ferry, which had been at risk of closure.”

  10. dearieme permalink
    April 19, 2016 2:18 pm

    Longer but not fiercer summers. Good-oh.

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