Warming, warning!

Gone is the second decade of the twenty-first century. Time for summaries for weather / climate freaks. Climatologists use a 30-year window as a reference period, therefore with the advent of 2021, the 1981-2010 benchmark period gives way to 1991-2020 window. I hence take the opportunity to run some comparisons of average temperatures in Warsaw measured across decades.

I rely on official, publicly available weather data for Warsaw for years 1951-2020 and for earlier period, on a spreadsheet which I downloaded back in 2010 from a NASA website, but could not restore the link. The database I had come by then traces back to 1881, however lacks measurements from years between 1938 and 1950, hence the analysis is a bit patchy.

The first chart shows how average temperatures in specific months rose in last three 30-year reference periods. The trend of rising temperatures is clearly visible, with the average temperature going up by around 1 Celsius degree, comparing 1991-2020 to 1971-2020 average.

The second chart illustrates average yearly temperatures in 30-year periods. One clearly sees the 1961-1990 period was not warmer than 1881-1910, but the heating-up process actually began in 1990s and accelerated in the current century.

The third graph shows even more vividly the growth of average yearly temperatures decade by decade. I firstly took 30 years for temperatures to grow by 1 Celsius degree, but then the pace accelerated to alarming 10 years per 1 Celsius degree.

On the fourth graph you can clearly see the mean monthly temperatures have not risen markedly between the 1881-1910 and 1951-1980 reference periods, which means temperature growth was observable, yet its pace was not upsetting.

But the fifth graph compares two reference periods which are only 40 years apart (vs. 70 years apart on the fourth graph) and here the difference is clearly visible and reaches 2 Celsius degrees in some winter and summer months.

The last, sixth graph shows the change of mean monthly temperatures in Warsaw in 30-year periods which are a century apart. Oddly enough, the difference is in some months lesser than on the fifth graph (1960s and 1970s are said to be a temporarily colder period on Poland with frosty winters and inclement summers), but I draw your attention to how the gap is spread. Average temperatures rose markedly (nearly 2 Celsius degrees) in winter and summer months, while in late spring and early autumn months, the scale of warming is visibly smaller (less than 1 Celsius degree). I wonder what the factors behind such tendencies are.

In this note, I have attempted to provide you with some raw data, with scant purely statistical commentary. Conclusions should you draw yourselves!