Climate Change in Denmark

As the fifth report from the Intergovernmental Panel on Climate Change (IPCC) is due soon in its final edition, we might take a look on what is happening right now in Denmark. Since the 1870s the Danish Meteorological Institute has been measuring temperature and precipitation while sea level records started around the first decade of the 1900s. Does these records show any signs of climate change or is it not showing in Denmark?
(All graphs from www.dmi.dk)

The annual mean temperature for Denmark which has been measured since 1873, shows a rising trend since the industrial revolution. In the last 140 years the temperature have raised itself by more than 1.5C. As the temperature pass the year 1980 the temperature jumped 1C in 30 years.

FIG 1: Annual mean temperature in Denmark since 1873. Values are calculated national average based on a number of selected stations. The curve in bold shows 9 years Gaussian Filtered values. Like global temperatures, a clear increase is seen in the annual mean temperature. Data is published in DMI's technical report series







As the temperature rises the yearly accumulated precipitation likewise has been
going up. The warmer air contains more water vapour which leads to more rain, extreme events, and hence a rising yearly accumulated precipitation as predicted in the report Turn Down the Heat: Why a 4°C Warmer World Must Be Avoided by the World Bank. We also notices that the five wettest years in Denmark all happened since 1990.

FIG 2: Annual precipitation in Denmark since 1874. Values are calculated national average based on a number of selected stations. The curve in bold shows 9 years Gaussian Filtered values. Data is published in DMI's technical report series.









Furthermore as the temperature rises and warms up the ocean, it expands and cause a change in sea level. In Denmark nine different stations have been measuring the sea level since the beginning of the 19th century and all show a remarkable sea level rise since the 1970s. But when the report Turn Down the Heat by the World Bank mention a 20 cm rise in the last 100 years we don't recognize it in Denmark, but as most of Denmark rising due to the glacial isostatic adjustment since the last deglaciation we are expecting a lower rise.

FIG 3: 19-year average of continuous mean value of sea level at 9 Danish stations stating the average rate of increase for the years 1901-2000 (uncertainty 0.2 mm/year). In the figure, mean value for the years 1960-1990 has been deducted. Figure taken from the academic record of changes in sea level in Denmark over the next 100-200 years by GEUS/DMI.






The isostatic adjustment raises the northern parts of Denmark while the south-eastern part is sinking. So 100 years of 1 mm rise pr year gives 10 cm and adding this result to the biggest difference from above sea level measurements gives a total of around 20 cm.

FIG 4: Vertical land movements (mm/year). The dotted line in grey shows the margin between two areas following different patterns of movement. This produces two 0-lines (Nissum Fjord-Nyborg-Præstø and Fano-Sonderburg-Gedser) where grounds neither increase nor decrease. Figures from the academic record of changes in sea level in Denmark over the next 100-200 years by GEUS/DMI.





We can conclude that the climate is changing and especially the last 30 years are showing a change. Even though the landmasses are rising in most of Denmark we still get a sea level rise, which is threatening our society. It will be getting warmer and wetter which might be good for our agriculture but also a big challenge for the cities with extreme rainfall and heat waves to secure a healthy infrastructure and avoid deaths.

And as the World Bank report Turn Down the Heat concludes, we must avoid a 4C warmer world.