Sizzling March?

By Paul Homewood

image

https://www.metoffice.gov.uk/hadobs/hadcet/cetmaxdly1878on_urbadj4.dat

 

According to CET, March 2019 was the 17th warmest on record since 1659, 1.2C higher than the 1981-2010 average.

Sound impressed? No, thought not!

The month as a whole actually seemed to be pretty unremarkable. There was some mild weather at the start of the month, accompanied by very wet weather. The last few days were also pleasant and sunny.

But unusually warm?

The graph at the top gives a bit of perspective.

First of all it is obvious that last month was pretty typical of Marchs during the last 30 years or so.

The fact that it is 1.2C above the 30-year average means little, as natural variability means some years are warmer and others cooler, such as last year. That’s what an average is.

Indeed, in the last 30 years, eleven had March anomalies of 1C or more. Six of these years were warmer than this March.

By far the warmest Marchs were in 1957 and 1938, again suggesting that there was nothing unusual about last month.

 

The other thing which stands out is that most Marchs used to be much colder than normal until the 1980s.

BTW, I use the term “normal” deliberately. The climate of the last 30 years or so is what we are used to, and it is also the standard definition of the WMO. Besides, why should the temperatures of the 18thC, for instance, be regarded as “normal”, particularly when we know the Little Ice Age was exceptionally cold historically.

 

 

Two more charts offer a good indication of what is happening.

First, the distribution of the hottest March days, those above 17C:

 

image

https://www.metoffice.gov.uk/hadobs/hadcet/data/download.html

 

This year did not even figure on the list, with a high of 14.5C.

Since daily figures became available in 1880, there is no evidence that top temperatures in March are getting higher, or that these warmest days are becoming more frequent.

 

When we look at cold extremes, however, a clear pattern emerges:

 image

 https://www.metoffice.gov.uk/hadobs/hadcet/data/download.html

 

March 2018 sticks out like a sore thumb with those four days at the right of the chart, one of which was the coldest March day in the whole series. (These are daytime temperatures, by the way, ie daily maximums, and not daily minimums).

But apart from last year, exceptionally cold March days have been virtually non existent since the 1970s. At the start of the series in the 1880s, they were very common.

 

When we look at the rise in monthly mean temperatures in recent decades, we are not observing days becoming warmer, so much as the coldest days becoming less common.

Put simply, our climate in March is much less extreme than it used to be.

via NOT A LOT OF PEOPLE KNOW THAT

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April 3, 2019 at 01:27PM

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