Climate change Germany
Air temperature changes until now
The annual average temperature increased by ca. 0.8 to 1.0ºC between 1900 and 2000. However, this warming did not occur linearly. A strong warming up to 1911 was followed by a heterogeneous period. The 1940s were exceptionally warm. After a cooling trend up to the 1970s we now observe a continuous and rapid temperature increase that still continues today (1).
During 1900-2000, temperature increase during spring, summer, autumn and winter was 0.8⁰C, 1.0⁰C, 1.1⁰C, and 0.8⁰C, respectively. During 1981-2000, temperature increase during spring, summer, and winter was 1.3⁰C, 0.7⁰C, and 2.3⁰C, respectively; during autumn there was a slight temperature decrease of 0.1⁰C (2).
The stronger temperature increase in winter than in summer during the last decades is often attributed to a higher frequency of zonal weather conditions in winter that bring mild oceanic weather to Germany (3).
Within the German side of the Rhine basin, both the daily minimum and maximum extreme temperatures have increased over the period 1958 to 2001, with the degree of change showing seasonal variability. On an annual basis, the change in the daily minimum extreme temperature was found to be greater than that of the daily maximum extreme temperature (11).
Extreme heat events, such as heat days (T > 30ºC) or heat waves (intervals of more than three days during which the maximum daily temperature lies above a certain high threshold, relative to the specific temperature standard of the weather station) exhibit a definite trend. For example, the probability of occurrence of heat days in the months of July and August has risen over the last one hundred years, and especially markedly during the last twenty years at almost all weather stations in Germany (4). The number of ice days (maximum temperature < 0 °C), however, has not changed significantly (19).
There is strong regional variation. The temperature increase observed since 1901 has been especially pronounced in south-western Germany. The mean annual temperature in the state of Saarland has risen by about 1.3°C, for example. In northeastern Germany, temperatures have not risen as sharply since 1901. In Mecklenburg – West Pomerania, for example, they have risen by only 0.6°C (12). Also in the last decade (1990s), the temperature rise in southern and southwestern Germany was exceptionally strong (1).
The extremely hot summer of 2003
The probability of occurrence of an extremely hot summer, such as in the year 2003, increased in the course of the 20th century by more than a factor of 20. Nevertheless, 2003 was an extraordinary year even for today’s standards. It was the hottest year in Germany since the beginning of weather recording. With summer temperatures of 3.4ºC above the 30-year mean, 2003 also exhibited the strongest summer anomaly. Moreover, the year 2003 was exceptionally dry. The continuing long-term dry phase between February and August was extraordinary (6).
Precipitation changes until now
During 1900-2000, yearly averaged precipitation increased by 9%. During this period precipitation decreased slightly in the summer (by 3%). During spring, autumn and winter precipitation increased by 13%, 9%, and 19%, respectively (2).
Precipitation in Germany is characterised by strong regional and seasonal variations, however. In the long term, neither the average values nor the seasonal or regional distribution show significant trends (4). During the last 100 years there has been a small trend towards increased winter precipitation, but this trend is not significant (5).
In the last 30 years, however, there was indeed a definite increase in winter precipitation. Summer precipitation in contrast showed little change. During 1971-2000, precipitation increased for all seasons: during spring, summer, autumn, and winter by 13%, 4%, 14%, and 34%, respectively. Yearly averaged precipitation increase during 1971-2000 is 16% (2). This trend can probably be attributed to an increased frequency of zonal circulation patterns in winter that bring plenty of precipitation with them (4). The winter trends are strongest in North-western Germany with an increase of up to 32 % over the period 1951 - 2006. The other regions experienced moderate increases over this period of 8 to 20 % (19).
The intensity and frequency of occurrence of extreme rainfall events have increased especially during the last forty years of the 20th century. In general, this trend is more pronounced in the winter than in the summer (7).
Within the German side of the Rhine basin, the daily extreme heavy precipitation has increased from 1958 to 2001 both in magnitude and frequency of occurrence in all seasons except summer, where it showed the opposite trend (11).
The number of dry days (days with less than 1 mm precipitation) in the summer increased by 5 to 20 %, especially in Eastern Germany; compared with 1955–1964 there are approx. ten days more per year in Eastern Germany without significant precipitation in this region. The number of dry days in the winter decreased slightly (up to 10 % in Southern Germany) (19).
At 177 weather stations throughout Germany snowdays decreased uniformly at a rate of 0.5 days per year during1950–2000 (18). Since 1950, a decrease by 30-40% in the duration of snow cover has been observed in altitudes below 300 m in Bavaria and Baden-Württemberg. In the medium altitudes (300-800 m) the decrease was 10-20%. In higher altitudes over 800 m only small decreases and in places even increases were observed, due to increased winter precipitation and sufficiently low temperatures for snowfall (3).
Wind climate changes until now
There is a tendency of increased probability of occurrence of extremely high daily wind speed maxima (Bft > 8) during winter (with the exception of coastal regions), and decreased occurrence of such maxima in summer (with the exception of southern Germany) (2). However, at present no statistically significant trend can be found (4,12).
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 (25). 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 (26).
Air temperature changes in the 21st century
Temperatures are expected to increase by 0.5 to 1.5°C in the period 2021 to 2050 with respect to 1961-1990 (16). According to several climate scenarios, long-term average annual temperature in Germany is projected to rise by 1.6 to 3.8ºC by the year 2080 (4). Regionally, many scenarios show a particularly strong warming in the south-west (19), and partly also in the far east of Germany. The scenarios show differences in seasonality. The trend of stronger warming in winter, which was observed in historical data, is not maintained in the future scenarios (4).
For the Elbe-watershed, a moderate warming of 1.4ºC by 2055 is projected (8). For Bavaria and Baden-Württemberg, temperature increases are projected for 2050 of 1.2 –1.7ºC in summer, and of 1.0 – 2.0ºC in winter (9). For Thuringia, a warming is projected of 1.5ºC in 2050 (10).
The numbers of summer days (T>25°C) could double by the end of the century, and the numbers of hot days (T>30°C) could even triple (12).
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 (17).
Precipitation changes in the 21st century
The short term (between now and 2040)
For Southern Germany, a region which is structured by several lower mountain ranges and river valleys including the upper parts of the Rhine and Danube, changes in mean and extreme precipitation were studied over the next decades (2011–2040) compared to the climate of the recent past (1971–2000). This was done through high-resolution regional climate simulations based on emission scenarios A1B and B1 (20). The results show that in winter, the study area becomes moister (in the order of 5–10%) like most of Northern Europe. The changes of extreme precipitation in winter are of the same magnitude. In summer, there is a slight decrease of precipitation in Central Europe for the near future, but this tendency towards dryer conditions is likely to become stronger towards the end of the 21st century (21). Most simulations suggest a trend towards more precipitation extremes in the summer in the near future for Central Europe in the sense of larger inter-annual variations, such as droughts and flood-prone years.
The long term (end 21st century)
Regarding annual precipitation, a study based on several climate scenarios shows only very little changes that mostly lie below 10% until 2080. Stronger changes become apparent when contrasting summer and winter precipitation: an increase in winter precipitation and (in most scenarios) a decrease in summer precipitation. This is in accordance with the observed trend of a shift of precipitation into winter (4).
In their 5th Assessment Report the IPCC presented a precipitation decrease at the end of the 21st century for April through September up to 10% for England, Belgium, the Netherlands and northern Germany, under the intermediate RCP4.5 scenario of climate change. These projected changes, however, do not exceed natural climate variability across the region. For October through March a precipitation increase up to 10% was projected for this North Sea region; these projected changes do exceed natural climate variability across the region (23).
Climate models show that precipitation volumes remain nearly constant on a yearly basis, while changes in precipitation cycles could well occur in Germany: summer precipitation, for example, could decrease by up to 40% nation-wide. The southwestern part of Germany might be particularly strongly affected by such decreases. In winter months, precipitation levels could increase by up to 40%, depending on what model is chosen (12,16).
The Deutscher Wetterdienst is currently using a model ensemble consisting of 8 driving global climate models and 11 regional climate models; for the period 2071 – 2100, 85 % of the analyzed model combinations project an increase in winter precipitation of up to 15 %, whereas a decrease of summer precipitation is projected up to 20 % (19).
Initial analyses indicate that the intensity of heavy precipitation events could increase (12). Heavy precipitation events are expected to significantly increase in frequency especially in Northern Germany (19)
Regionally the most distinct increase of winter precipitation is projected for southern Germany. Decreasing summer precipitation in these scenarios is concentrated on Southwest Germany (Rhineland) and the central parts of Eastern Germany. However, the projections of different climate models partly produce regionally contradicting trends (4). For Central Eastern Germany, regional climate model projections for 2071-2100 (emission scenario A1B) indicate that precipitation totals and the frequency of heavy precipitation events will probably increase during most seasons, whereas summers are projected to become considerably drier (22).
For the Elbe-watershed, a decrease in precipitation of up to 200 mm by 2055 is projected, particularly in summer (8). For Bavaria and Baden-Württemberg, changes in precipitation by 2050 range from +5% to +13% in summer, and from 0% to +34% in winter (9). For Thuringia, a precipitation increase of 23% in the winter, and a precipitation decrease of 8% in the summer is projected in 2050 (10).
Some model results indicate that in the winter seasons towards the end of this century there could be up to 70% more rainfall in the central upland regions of rhineland-palatinate, hesse and the north-east of Bavaria (16).
Projections of climate change show a future decrease in mean annual maximum snow depth everywhere over Northern Europe. 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 (13).
Wind climate changes in the 21st century
As to the frequency of storm days, initial studies show no changes from current conditions (12) or too many uncertainties to permit clear forecasts (16). Some researchers, however, 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 (14,15).
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 (24).
Uncertainties in climate projections
In comparison of the different climate models, uncertainty appears much larger in projections of precipitation than of temperature. Particularly the regional distribution of precipitation trends varies strongly (4).
Uncertainties in model results
On long time scales, the uncertainty within climate modeling of temperature changes is smaller than the variation brought about by different emission trajectories (4).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Germany.
- Rapp (2000); DWD (2004), both in: Zebisch et al. (2005)
- Jonas et al. (2005), in: Zebisch et al. (2005)
- Günther (2004), in: Zebisch et al. (2005)
- Zebisch et al. (2005)
- Müller-Westermeier (2001), in: Zebisch et al. (2005)
- Schönwiese et al. (2003), in: Zebisch et al. (2005)
- Grieser and Beck (2002), in: Zebisch et al. (2005)
- Wechsung et al. (2004), in: Zebisch et al. (2005)
- Weber (2004), in: Zebisch et al. (2005)
- Thüringer Landesanstalt für Umwelt und Geologie (2004), in: Zebisch et al. (2005)
- Hundecha and Bárdossy (2005)
- Government of the Federal Republic of Germany (2010)
- HELCOM (2007)
- Woth et al. (2005), in: Alcamo et al. (2007)
- Beniston et al. (2007), in: Alcamo et al. (2007)
- Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (2009)
- De Vries et al. (2012)
- Kreyling and Henry (2011)
- Becker (2012)
- Feldmann et al. (2013)
- Solomon et al. (2007), in: Feldmann et al. (2013)
- Schwarzak et al. (2015)
- IPCC (2013), in: May et al. (2016)
- May et al. (2016)
- Feser et al. (2015a), in: Stendel et al. (2016)
- Ulbrich et al. (2009); Feser et al. (2015a), both in: Stendel et al. (2016)