Climate change Norway
Air temperature changes until now
For the period 1900-2008 as a whole, the annual mean temperature in Norway has increased by about 0.9°C. Dependent on geographical region, the increase in annual temperature varies from 0.5 to 1.1°C. The largest increase is found during spring, where the mean temperature has increased by 0.7-1.4°C. Also in Svalbard, observations from the last hundred years tend to show a positive trend in temperature. A composite series of temperature from 1912 to 2008 shows a linear trend of 2.3°C per century (1).
In Oslo, the annual mean temperature has increased by 1.5 ∘ C in the period 1838 – 2012. The temperature has increased significantly in all seasons; however, the temperature increase in summer was less than a half of that in winter and spring, which were the seasons with largest increase. In addition the monthly mean temperature of the coldest month in each year has increased two times faster than the warmest one (19).
Urban heat island
The urban heat island effect has been studied for Fennoscandia, the northern half of Norway, Sweden and Finland, and including the adjacent part of Russia. This study includes all 57 cities located above 64° N in this region. Data covering the period 2001-2017 show that the mean urban heat island intensity is found in the range 0-5°C. The intensity is larger for the largest cities of Murmansk and Oulu (3-5°C) (25).
Precipitation changes until now
Because of prevailing westerly winds, moist air masses flow regularly in from the ocean giving abundant precipitation over most of Norway. Areas just inside the coast of western Norway get most precipitation. This zone of maximum precipitation is one of the wettest in Europe, and several sites in this region have normal annual precipitation of more than 3500 mm. On the leeward side of the mountain ranges the annual precipitation is much lower, and a few sheltered stations in south-eastern Norway and Finnmarksvidda have normal annual precipitation less than 300 mm (1).
The annual precipitation has increased in Norway during 1900-2008. The largest increase (19-22%) is found in western and north-western Norway. In southern regions the precipitation increase is largest during autumn, while in northern regions it tends to be larger during winter. Also in Svalbard, observations from the last hundred years tend to show a positive trend in precipitation. A composite series of precipitation from 1912 to 2008 shows a linear trend of 24% per century (1).
Data for the period 1957 to 2010 show that the intensity of strong precipitation events has increased in most parts of the country, and patterns are more apparent for longer-duration precipitation. Also the frequency of moderate to strong precipitation events has increased in most parts of the country since 1957 (mainly between 10 and 30%), particularly in wet regions. Increased winter precipitation and temperature has led to more snow in cold areas and less snow in warm areas (18).
Snow cover has decreased in the northern hemisphere for the past 50 years (2). Investigations in the Nordic countries show that in Finland, snow water equivalent (SWE) has been increasing in the eastern and northern part during 1946 - 2001, whereas there was a decrease in SWE in the southern and western part (3). An overall decrease in snow depth has been found in Norway for three eastern sites located south (Gardermoen), in the middle (Røros) and in the north (Finnmark) respectively (4).
Snowfall depends strongly on temperature and precipitation. In Norway, both variables have in creased during winter in the past few decades. There is a tendency to an increase in so-called snow days in cold (mountainous) areas and a decrease in warm areas (central Norway, and along the southern coast (18).
Glacier changes until now
The Norwegian coastal glaciers, which were expanding and gaining mass due to increased snowfall in winter up to the end of the 1990s, are also now retreating, as a result of less winter precipitation and more summer melting (12, 13). Nearly all the smaller Norwegian glaciers are likely to disappear and overall glacier area as well as volume may be reduced by about one third by 2100 (14).
Wind climate changes until now
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 (22). 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 (23).
Air temperature changes in the 21st century
Projections of climate change for Norway have been presented with respect to the present climate (period 1961-1990) and two scenario periods (2021-2050 and 2071-2100) (5). These projections are based on statistical and dynamical downscaling of global climate model results from IPCC (2001, 2007). The projections indicate a warming in all parts of Norway and during all seasons from 1961-1990 to 2071-2100. The annual mean temperature for Norway is estimated to increase by 3.4ºC (2.3-4.6ºC). For the Norwegian mainland, the largest annual temperature increase 4.2ºC (3.0 – 5.4ºC) is estimated for the northernmost county (Finnmark) and the smallest 3.1ºC (1.9-4.2ºC) for Western Norway (5).
The largest temperature increase is projected for the winter season, and smallest increase during summer. The growing season is projected to increase by 1-2 months over large parts of the country (5).
Projections for 2025
For 2025 projections have been calculated for changes in temperature and precipitation compared to the reference period 1961-1990, based on several simulations with a large number of regional models. The results for temperature are (15):
- 1.5ºC to 2.2ºC temperature increase in autumn and winter, with the biggest changes simulated for northern Norway and the smallest on the west coast. The spread among the different models is larger in winter than autumn. The difference between the model with largest and smallest change is typically 1ºC in winter and 0.5ºC in autumn;
- 1.1ºC to 1.7ºC temperature increase in summer and 1.6ºC to 2.1ºC in spring. Summertime changes are generally 30% smaller than wintertime changes in northern and middle Norway and 10% smaller in southern Norway while springtime changes are comparable to wintertime changes in southern Norway and slightly smaller in northern regions. The spread among the different models are similar in summer and spring. The difference between the model with largest and smallest change is typically 0.8ºC.
- the models predict future warming to proceed with approximately the same speed as observed over the last 40 years (Hanssen-Bauer (2005)). The pattern of greatest warming in northern (inland) regions also seems to be present in the observations.
Projections for the end of the 21st century
According to projections reported for the period 2071-2100 compared with 1961-1990, maximum temperature in summer will increase most in the south-east, with 3⁰C and about 2⁰C in rest of the country (6). The number of hot summer days will also increase (mostly in the southeast) and the winters will be milder with minimum temperatures between 2.5 and 4⁰C above present values. The largest increase is expected in the region of Finnmark.
For Svalbard the increase in annual temperature up to the end of the 21st century varies from ca. 3ºC in the southwest and ca. 8ºC in the northeast (1). The projected warming is smallest for the summer season and greatest for autumn and winter. Substantial increase in air temperature is also projected for the ocean areas between Svalbard and Novaja Zemlja. This increase is greatest in areas where sea-ice is replaced by open water (7).
Air temperature changes in the Arctic in the 21st century
Global climate model simulations (8) indicate that up to the end of the 21st century, Arctic temperature is projected to increase by 7ºC and 5ºC for the A2 and B2 emission scenarios, respectively. The strongest warming will occur during autumn and winter. The Multi-Model Dataset used in the regional climate projections for IPCC (2007) projected an annual warming of the Arctic of 5ºC at the end of the 21st century.
There are large discrepancies in how different global and regional climate models describe both present and future ice conditions in the Norwegian Arctic, and the uncertainties in the Arctic climate projections are thus considerable (1).
Climate change simulations up to year 2050 indicate an increase in annual temperature of approximately 1ºC in the coastal areas in Nordland and Troms, and between 1.5-2.0ºC in eastern parts of Finnmark and southwest of Spitsbergen (1).
Changes in summer and winter length in the 21st century
For northern Europe, season lengths have been quantified for the period 2040-2069, under a moderate scenario of climate change (the RCP4.5 scenario) and based on a large number of global climate models. Changes have been compared with the seasons in 1971-2000 for reference. This scenario corresponds to 2°C global warming in 2040-2069 relative to the preindustrial climate. In northern Europe, warming exceeds this global mean substantially, however (24).
According to these model projections, the summer (daily mean temperature > 10°C) will last about a month longer by mid-century in most of Northern Europe. The summer is projected to start 2 weeks earlier and last two weeks longer. In the very coldest areas, the mountains, northern Lapland and the coasts of the Arctic Ocean, summer lengthening may be even more than 30 days. Concurrently, the projections show that winter (daily mean temperature < 0°C) will become shorter by 30-60 days. Winters are projected to start 15-30 days later and end 15-30 days earlier. Changes are largest near the coasts of the Arctic Ocean and the Baltic Sea, and relatively modest in the northern inland areas. Standard deviations of the model projections are about 10 days for the lengths of the spring, summer and autumn, and 10-25 days for winter length. In Denmark and southernmost Sweden, the average winter is already quite short now and there is little room for further shortening. By mid-century, the probability of missing winters will increase considerably, particularly in southern Sweden and the Baltic countries (24).
Precipitation changes in the 21st century
Projections for 2025
For 2025 projections have been calculated for changes in temperature and precipitation compared to the reference period 1961-1990, based on several simulations with a large number of regional models. The results for precipitation are (15):
- precipitation increase is projected for all regions compared to the reference period 1961-1990 and range from 3% to 17% in winter and 5% - 15% in spring in different regions. In winter the largest changes are simulated for the south-eastern parts of Norway while the smallest are in coastal areas in northern and middle Norway. The situation is opposite in the spring, with the largest increase in middle Norway (14-15%) and the smallest in south-eastern parts of Norway and the northernmost parts (5-9%). For both seasons, the intermodel difference in amplitude of the change is large.
- the relative change precipitation in 2025 in different regions compared to the reference period 1961-1990, ranges from -11% to 10% in summer and 0 to 11% in autumn. In summer the southern parts of Norway are simulated to be dryer compared to the reference period (up to 7-11%). In autumn there is an increase in the whole country (except one region) compared to the reference period. The increase is less than 10% in all but one region. As for summer the largest increase is simulated for middle Norway with 9-11% and the smallest for the southern parts of Norway with 0-3%.
- the observed changes in precipitation seen over the last 40 years are unprecedented in the 100 years of observations that is available. If the trend continues one would experience annual precipitation changes in the order of 30% in hundred years. This is 2-3 times higher than what is projected in this study.
Projections for the end of the 21st century
Annual precipitation averaged over the Norwegian mainland is estimated to increase by 18% (5-30%) up to the year 2100 with respect to 1961-1990 (5). The largest seasonal precipitation increase in 2100 is 23% (5-33%) for the autumn, while the smallest increase of 9% is found for the summer season. For the summer season the low estimate indicates a reduction (-3%) in the total precipitation for the Norwegian mainland, while the high estimate gives an increase of 17%. The low estimate gives reduced summer precipitation over all regions in Southern Norway, and in the southernmost part a reduction of ca. 30% (5).
The tendency of drier summers in the south of Norway reflects the conditions projected for summertime central and southern Europe. Except for the summer precipitation, the seasonal precipitation is projected to increase in all seasons and in all regions. The average projection indicates more days with heavy rainfall and higher precipitation values in the extreme events all over Norway and in all seasons. This is also valid for the summer season in the regions where the total summer precipitation is projected to be reduced. During winter and autumn the number of days with heavy rainfall may be twice the present level (5).
The snow season is projected to be shorter all over the country. A reduction of 2-3 months is estimated for low-elevation areas. Up to mid-21st century, the maximum snow water equivalent during the winter season may increase in the high-mountain regions and in areas in interior parts of Northern Norway (5). As the winters become shorter, snowfall in autumn and spring months is reduced. In the middle of the winter, snowfall may increase in the coldest regions. Even in the areas where snowfall is projected to increase in the middle of the winter, the total annual snowfall is generally projected to decrease, although the change is small in the coldest regions of northern Europe (20).
In Norway, the largest change in snow season duration is projected along the coast, and especially in the innermost parts of the coastal areas in West Norway, Mid Norway and North Norway. A reduction of more than 80 days is projected in these areas from current (1961-1990) to future climate (2071-2100) (9).The decrease in the duration of the snow season is smaller with increasing altitude and distance from the coast. In some mountainous areas, we expect more snow especially in extreme wet years (10).
The variability of the extreme precipitation volumes may increase more than the mean precipitation, suggesting an increased showery nature of precipitation (11).
Precipitation changes in the Arctic in the 21st century
Climate change simulations up to year 2050 indicate an increase in annual precipitation from 1981-2010 to 2021-2050 of 20-30%, while for north-eastern parts of Spitsbergen the increase is up to 40%. The seasonal precipitation is projected to increase over the whole region during all seasons, with the largest increase during winter and spring. It should however be stressed that precipitation is quite scarce in this region during the winter season, implying that despite the large percentage increase the absolute increase in precipitation may be just a few millimetres (7).
Wind climate changes in the 21st century
Climate change projections give small or no changes for average wind speed in the year 2100 with respect to 1961-1990 (5). Recently, a study has been carried out where mean and extreme geostrophic wind speeds in Northern Europe were projected for the future periods 2046–2065 and 2081–2100, and compared with the baseline 1971–2000 (based on nine global climate models and the SRES A1B, A2 and B1 scenarios) (16). The geostrophic wind speed is a theoretical, calculated wind speed indicative of true surface wind speed. The results show:
- Mean geostrophic wind speeds: During the windiest time of the year, the monthly mean wind speeds will start to increase in the Baltic Sea already in 2046–2065. In Finland, increases are largest (5–7%) in November and January by 2081–2100. In November–February 2081–2100, a positive shift of 5–10% is projected to materialize in the Baltic Sea.
- Extreme geostrophic wind speeds: The extreme wind speeds (10-year return level estimates) will increase on average by 2–4% in the southern and eastern parts of Northern Europe, whereas a decrease of 2–6% dominates over the Norwegian Sea. These results agree with results on the future projections of 20-year return level estimates of gust winds that showed that the increase in winds is dominant in a zone stretching from northern parts of France over the Baltic Sea towards northeast (17).
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 (21).
Sea water temperature changes in the 21st century
Thickness and area of the Arctic ice cover will continue the present tendency of reduction. The Arctic may be ice-free during summertime in the middle of this century, but a substantial variability is expected both on annual and decadal time-scales (1).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Norway.
- Ministry of the Environment of Norway (2009)
- Lemke et al. (2007), in: Bache Stranden and Skaugen (2009)
- Hyvärinen (2003), in: Bache Stranden and Skaugen (2009)
- Dyrrdal (2008), in: Bache Stranden and Skaugen (2009)
- Hanssen-Bauer et al. (2009), in: Ministry of the Environment of Norway (2009)
- presented by Gjershaug et al. (2009)
- Førland et al. (2009), in: Ministry of the Environment of Norway (2009)
- ACIA (2005),in: Ministry of the Environment of Norway (2009)
- Vikhamar-Schuler and Førland (2006), in: Gjershaug et al. (2009)
- Bache Stranden and Skaugen (2009)
- Skaugen et al. (2003)
- Nesje et al. (2008), in: EEA, JRC and WHO (2008)
- Andreassen et al. (2005), in: EEA, JRC and WHO (2008)
- Nesje et al. (2007), in: EEA, JRC and WHO (2008)
- Sorteberg and Andersen
- Gregow et al. (2011)
- Nikulin et al. (2011), in: Gregow et al. (2011)
- Dyrrdal et al. (2012)
- Nordli et al. (2015)
- Räisänen (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)
- Ruosteenoja et al (2020)
- Miles and Esau (2020)