Sunday, 1 December 2019

What’s wrong with the average

November 2019, with mean temperature of +6.3C has gone down in the history as the warmest November in Warsaw after WW2 and second-warmest since records began, after November 1926 when temperature averaged out whopping +7.5C and ahead of November 1928 with average temperature of +6.2C.

For the sake of statistics, since the recent month will not become a part of the tenth edition of the renowned winter timeline:
- month-time high: +16.5C on 4 November 2019 (almost 3 degrees below last year’s record of November heat)
- month-time low: –4.7C on 1 November 2019 (was a frosty night, followed by nearly 3 weeks of above-average warmth),
- the warmest day: 4 November 2019 (daily average of +13.5C, typical late September’s weather, though windy),
- the coldest day: 23 November 2019 (daily average of –0.2C, technically a one-day thermal winter).

Also for the record, several trees, including birches, poplars, maples and willows have not shed their all leaves.

If you look at the graph showing average temperatures of Novembers in Warsaw in 21st century against long-term average, you can see only 4 out of 19 Novembers were below the average, therein 3 less than 1 Celsius degree below it. For the sake of clarity, in Polish climatology, the average temperature is based on recent finished full three decades, hence the frame of 1981-2010 currently serves as basis for what could be considered “normal”.

Another graph compares mean temperatures of specific months in 2019 against long-term average. As it turns out , May was the only month this year with temperature below average (by 0.5C degree), while January and July were just above the average (respectively by 0.1C and 0.2C degree). 2019 is bound to go down as the warmest year in Poland since records began…

…And will beat the record set by 2018, when only February and March brought below-average temperatures, while other months were substantially warmer than historically, including especially two spring months the warmest since records began: April 2018 (mean temperature of +13.6C, beating the record of +13.5C from April 1918) and May 2018 (mean temperature of +18.2C, above May 1937 when temperature averaged out +17.8C).

While CEE countries experienced a balmy late autumn, the Western part of Europe was shivering (for around two weeks temperature in Warsaw was constantly higher than in Madrid), Venice was plagued by the most horrible flood since decades, snow fell in mountain areas of North Africa and northern Scandinavia experienced the heaviest early-November snow (nearly one metre) since 1922. The bill for our warmth was paid in other parts of the planet; unsurprisingly, since the global warming exacerbates imbalances in the atmosphere and conceivably in a year or two we might be hit by an onslaught of winter in mid-November.

I also wondered how switching to a refreshed long-term average in 2021, i.e. replacing 1981-2010 with 1991-2020 timeframe would impact “normal” mean temperatures and here comes the comparison (with averages based on 1991-2019 data). The green spots referring to the right axis show the temperature increase. Sadly, the biggest warming is observed in summer months (June and August) when heat is the hardest to withstand and through energy-consuming use of cooling systems intensifies the process of warming. Besides, many colder months have become on average milder, i.e. November, February and December. Interestingly, average temperature of October would rise by merely 0.1 degree and this is despite the string of 3 warm Octobers since 2017.

While around autumn the oncoming winter was predicted to be the mildest ever, in the recent (issued a week ago or so) long-term forecast of the Polish Met Office only December 2019 is to be warm. Polish forecasters predict January 2020 and February 2020 will bring proper winter, including snow and double-digit frosts, while mean temperature of March 2020 will be close to long-term average.

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