Heat wave definitions: if one doesn’t suit us, we will take another one

Last week we had a heat wave in Belgium. But just a day before it officially became a heat wave, it was already connected to Global Warming. The alarmist on duty is Jill Peeters, a Flemish weather woman: Jill Peeters warns: a heat wave like this one will occur once every 3 years (Dutch). In it a graph that shows heat waves in De Bilt (The Netherlands) are on the rise:

heatwave climate central

That’s odd. I have been looking for some time at the heat wave data of Belgium and the Netherlands, but as far as I could see there was no reason for alarm, on the contrary. This was nothing like I have seen in the heat wave data of the De Bilt weather station. Where did they get this result?

In a tweet she linked to Climate Central that described the analysis. They tried to find out how likely heatwaves became using “observational weather and climate data, weather forecasts and climate models”. Color me unimpressed.

Apparently they also were in quite a hurry, beside observations, they used forecasts and they presented their result in the beginning of the period in which heat waves occur and apparently couldn’t wait for a couple days… This made me guess there is an hidden agenda here. It is definitely not scientific.

This was their definition of a heat wave:

the heat wave was defined as the average of the maximum temperatures over 3 consecutive days

For the record, this is the official definition of a heat wave in Belgium and in the Netherlands:

A heat wave is a sequence of at least five summer days (maximum temperature of 25 °C or higher) of which at least three tropical days (maximum temperature 30 °C or higher).

For being official, in Belgium this temperature has to be measured in Uccle and for the Netherlands in De Bilt.

For being a weather woman she has quite some difficulties to grasp the concept of a heat wave. Last year she declared a heat wave with temperature data from De Kempen (warmer and not comparable with Uccle). This year she comes with yet another definition to declare the alarm… Where does she keep getting all those different definitions?

What’s next? The 4-day average maximum temperatures? The 2-day average maximum temperatures? The maximum temperatures on July 6th?

That reminds me of the vague definitions of “Global Warming” and “Climate Change”. Global warming could for example be defined as the global mean temperature which is rising. But equally could be defined as an area having higher temperatures (for example Europe, the Contiguous United States,…). Or an historical temperature increase (it is now warmer than in say 1950s or 1880s,…). That way whatever comes on our path, global warming could always considered a fact. If the global mean temperature doesn’t cooperates, one area could well have a higher temperature (like Western Europe last week). Or one could point to the historical increase.

The same with climate change. What is it exactly that is changing? If temperature isn’t changing, it could well be precipitation, or snow, or … If the definition is not clear, anything can prove everything. We see that on a regular basis in the media.

The same with the heat wave definition. We can define heat waves as the combination of a period and intensity in a certain place. Or a period/intensity in a different (warmer) place. Or as an average over a three day period. Or … The different definitions will give a different result, but yet it called with the exact same name.

Can you imagine the confusing that comes out of this, the different parties are in fact talking about different things although they use the same words, but it also has the disadvantage that it will be difficult to compare and of course, it keeps the alarm alive.


3 thoughts on “Heat wave definitions: if one doesn’t suit us, we will take another one

  1. Hugh

    “one area could well have a higher temperature (like Europe last week).”

    Last time I checked, Finland was very much in Europe and _definitely_ no heat wave here. (or in Sweden, Norway, Iceland or…) But of course, for the noble cause I could talk about extreme cold due to climate change. Or of those poor bumblebees.


  2. Pingback: These items caught my eye – 13 July 2015 | grumpydenier

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