CET Temperature Trends In April
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.