Climate change Denmark
Mean temperature is approaching 8.5°C, an increase of almost 1.5°C since the end of the 19th century. Now, the average winter temperature is most often warmer than 2ºC and the average summer temperature is about 16ºC. The annual precipitation measured in Denmark is now about 750 mm. Precipitation is greatest in west and southern Jutland, with almost 1000 mm, and least on the eastern islands, where about 600 mm is recorded each year (8).
Air temperature changes until now
Since 1988, almost every year has been hotter than normal, and the temperature showed a sharply rising trend in the 1990s. Over the last 125 years, the temperature in Denmark has risen by almost 1.5ºC. This increase is more than double the increase in the global mean temperature for the same period (2).
In terms of cold-temperature events, there has been a strong decrease in the number of days with a minimum temperature below 0°C in the second half of the 20th century, exceeding 8 days per decade at some places in Denmark (3).
Part of the major climate changes observed in the Baltic Sea region during the late 20th century has been related to changes in atmospheric circulation. Is has been suggested that the increased frequency of anti-cyclonic circulation and westerly wind types have resulted in a slightly warmer climate with reduced seasonal amplitude and reduced ice cover (4). Recent research using tree-ring based chronologies indicates that the variability of recent decades may lie within the natural range (5).
Precipitation changes until now
Average annual precipitation varies greatly from year to year and from place to place. The lowest annual precipitation for the country as a whole was 464 mm in 1947, and the highest was 905 mm in 1999. The annual precipitation measured in Denmark is now about 750 mm. This has increased by about 15% - or 100 mm – since records began in 1874. It is typical that wet areas experience the greatest percentage increase: precipitation has increased most in west Jutland, by about 20% in the past 85 years (2). The frequency of extreme rainfall events in Denmark shows both a general increase from 1874 to present and a cyclic pattern with a period of 25–35 years (11).
Wind climate changes until now
The number of days with severe wind (>10.8 m/s) varies from about 30 in some places inland to almost 170 days at Skagen. On average, storm-force (>24.5 m/s) occurs along the Danish coasts every three to four years. In December 1999 large parts of Denmark were hit by the worst-ever measured hurricane, and in some places mean wind velocities (averaged over 10 minutes) of more than 40 m/s were recorded, with gusts of more than 50 m/s (2).
There is a tendency towards more powerful storms in Denmark. Since 1971 there have been 14 hurricanes and hurricane-like storms, as many as in the preceding 80 years (1). Direct wind observations from Skagen in northern Denmark, however, suggest decreasing overall storminess for the period 1860 - 2012 with extremely high storminess prior to 1875 (17).
A northward shift in mean storm track position since about 1950 is consistent in studies on wind climate in northwestern Europe over the last decades (16). This northeast shift together with the trend pattern of decreasing cyclone activity for southern mid- latitudes and increasing trends north of 55 - 60°N after around 1950 seems consistent with scenario simulations to 2100 under increasing greenhouse gas concentrations (18).
Air temperature changes in the 21st century
For Denmark, a future annual mean warming by the end of the 21st century was projected of 1.0, 1.8, and 3.7 °C for a low (RCP2.6), intermediate (RCP4.5) and high-end scenario (RCP8.5) of climate change, respectively (12). For more information on these scenarios: see page Europe/climate change.
Earlier analyses with global and regional climate models showed the following general changes for temperature in Denmark in the period 2071-2100 in relation to 1961-1990:
- A rise in the annual mean temperature of 3-5°C, depending on the chosen scenario for emissions of greenhouse gases. Greatest warming at night and no major difference between the increase in summer and winter. Warming leads to fewer days with frost and snow and less days with snow cover. Average snow cover decreases to about 25% of present-day values (8).
Plant growing seasons will be extended by 1-2 months on average (2). Both the frequency and the length of heat waves will increase (1).
Future cold spells in Western Europe are projected to become about 5°C warmer (and remain above freezing point), thus having a significant climatic impact. This conclusion is based on research in which a cold spell (CS) is defined as a non-interrupted sequence of days in which the 5-day average temperature falls below a threshold value Tcold (10).
In much of the North Sea region the number of tropical nights at the end of this century may rise by about 10 days under an intermediate (RCP4.5) and by more than 20 days under a high-end (RCP8.5) scenario of climate change, with tropical nights hardly ever occurring in this region under the present-day climate. Similarly, cold spells are projected to become shorter in the North Sea region, by about 3 days for the intermediate (RCP4.5) and about 4-6 days for the high-end (RCP8.5) scenario. Warm spells are projected to become markedly longer in the North Sea region, by about 30 days for the intermediate and by 60-120 days for the high-end scenario (13).
Precipitation changes in the 21st century
Analyses with global and regional climate models show the following general changes for precipitation in Denmark in the period 2071-2100 in relation to 1961-1990:
- An increase of 10-40% in winter precipitation and a reduction in the order of 10-25% in summer precipitation. A clear tendency towards more episodes with very heavy precipitation, particularly in autumn and lengthy dry periods, especially in the summer (8).
Under a high-end (RCP8.5) scenario of climate change annual mean precipitation is projected to increase by about 7% at the end of this century. Under this scenario an increase of 18% is projected for mean winter precipitation, and an increase of 10-11% is projected for spring and autumn. For summer, however, a decrease of about 17% is projected (12).
The IPCC presented somewhat different results in their 5th Assessment Report: a precipitation increase for April through September at the end of the 21st century up to 10% for Denmark and southern Norway (under an intermediate scenario of climate change). These projected changes, however, do not exceed natural climate variability across the region. For October through March also a precipitation increase up to 10% was projected for Denmark, under the same scenario for the end of the 21st century; these projected changes do exceed natural climate variability across the region (14).
At the end of the 21st century, extreme downpours are expected to be about 20% stronger than today (1).
Projections of climate change show a future decrease in mean annual maximum snow depth everywhere over Northern Europe. This decrease is smaller in the northern parts of the Baltic Sea basin than in the southern areas. The simulations also show a decrease in the duration of the snow season. In areas such as Denmark, Germany, Poland, and most parts of the Baltic countries, where the present-climate snow depth is small, the scenario simulations show a complete lack of snow cover (3).
Wind climate changes in the 21st century
Analyses with global and regional climate models show the following general changes for wind climate in Denmark in the period 2071-2100 in relation to 1961-1990:
- A tendency towards more frequent westerly winds and at the same time a shift of the storm tracks over the North Atlantic slightly eastward, leading to a small increase in storm activity over Denmark and the adjacent waters. On this basis, calculations with storm surge models show that the highest sea level in the more extreme cases could rise by 5-10% relative to today (about 0.3 m on the west coast) (9). In addition to this there is the global rise in sea level which the IPCC estimates at between 0.1-0.9 m over the level today (8).
The average wind speed is expected to increase by 1%–4% in the period 2071-2100 compared with 1961-1990, while the maximum storm strength is expected to increase on both sea and land, i.e. by 10% (1).
Some researchers conclude that more North Sea storms might be generated leading to increases in storm surges along the North Sea coast, especially in the Netherlands, Germany and Denmark (6,7).
A review of recent scientific literature shows that the projected changes in wind extremes (speed and direction) for the North Sea region are typically within the range of natural variability and can even have opposite signs for different scenarios either simulated by different climate models or for different future periods (15).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Denmark.
- Danish Government (2008)
- Danish Ministry of the Environment (2005)
- HELCOM (2007)
- Omstedt et al. (2004)
- Esper et al. (2002), in: Omstedt et al. (2004)
- Woth et al. (2005), in: Alcamo et al. (2007)
- Beniston et al. (2007), in: Alcamo et al. (2007)
- Danish Ministry of Climate and Energy (2010)
- Kaas et al. (2001); Christensen (2005), both in: Danish Ministry of Climate and Energy (2010)
- De Vries et al. (2012)
- Bülow Gregersen et al. (2015)
- DMI (2014), in May et al. (2016)
- Sillmann et al. (2013), in: May et al. (2016)
- IPCC (2013), in: May et al. (2016)
- May et al. (2016)
- Feser et al. (2015a), in: Stendel et al. (2016)
- Clemmensen et al. (2014), in: Stendel et al. (2016)
- Ulbrich et al. (2009); Feser et al. (2015a), both in: Stendel et al. (2016)