Temperature trends since 1900 in and around Roskilde
Using data from the European Centre for Medium-Range Weather Forecasts, we analysed 118 years of weather data in and around the city of Roskilde. The area analysed also includes the surroundings of Roskilde, which might include mountains or bodies of water, so that the temperatures shown here do not correspond exactly to the temperatures recorded by the weather stations of Roskilde (see Methodology for details). This is what we found:
The temperature in and around Roskilde between 2000 and 2018 was 1.5°C above the 20th century average.
The number of freezing days (below −1°C over a 24-hour average) went from 37.2 days per year in the 20th century to 23.1 per year since 2000.
Since 1900, the average temperature in and around Roskilde increased from an average of 7.7°C between 1900 and 1999 to an average of 9.2°C between 2000 and 2018. The warmest years in and around Roskilde were 2014, 2018, 2008, 2007, and 1990.
Temperature in and around Roskilde from 1900 to 2018. (png|svg|eps)
Number of days when the average temperature was above 21°C in and around Roskilde, each year. (png|svg|eps)
Temperature averaged −1°C or less for 37.2 days per year in the 20th century, on average. Between 2000 and 2018, the number of freezing days were 23.1 per year.
Number of freezing days in and around Roskilde, each year. (png|svg|eps)
What does it mean for Roskilde?
Roskilde and its environs in context
Roskilde and nearby cities
Here are the five locations closest to Roskilde, among the 558 we analyzed:
Roskilde — +1.5
Copenhagen 30 km +1.5
Næstved 56 km +1.7
Helsingborg 58 km +1.5
Lund 69 km +1.4
Odense 110 km +1.5
Cities of Denmark
Roskilde is one of ten locations in Denmark we have analyzed. This is how temperature has changed in the rest of them.
Næstved +1.7
Copenhagen +1.5
Roskilde +1.5
Odense +1.5
Aarhus +1.4
Aalborg +1.3
Kolding +1.2
Vejle +1.1
Randers +1.1
Esbjerg +1.1
Cities of Denmark(png|svg|webp)
Both data sets are re-analysis, which means that ECMWF scientists used observations from a variety of sources (satellite, weather stations, buoys, weather balloons) to estimate a series of variables for squares of about 80 kilometers in side width (125 kilometers for ERA-20C). While weather stations offer a much better record for immediate daily observations, using the ECMWF re-analyses is much more adequate for the study of long-term trends. Weather stations might move, or the city might expand around them, making their data unreliable when looking at centennial trends. However, the ECMWF data does not take into account micro-climates or "heat island" effects, so that the actual weather in the streets of Roskilde was probably one or two degrees warmer than the values reported here (the trend, however, is the same).