Air temperature changes until now

During the period 1881-2008, the average annual air temperature in Slovakia increased by about 1,6⁰C (5).

In central and western Europe, both the warm and cold tails of the temperature distribution in winter warmed over the entire 20th century. … Warming of winters during 1946-1999 occurred in both the warm and cold tails for both Tmax and Tmin, with the largest warming in the cold tail for Tmin. … There is more evidence for summer warming in the first half of the century compared with the second half (2).

Precipitation changes until now

During the period 1881-2008, average annual precipitation totals in Slovakia decreased by about 3.4%. In southern Slovakia the decrease was more than 10%, in the north and northeast an increase of up to 3% was documented (5). In the period 1995-2010, a significant increase in the occurrence of extreme daily precipitation totals has been observed, resulting in a higher risk of local floods in several localities of the Slovak Republic. On the other hand local and regional droughts caused by long periods of relatively warm weather and small precipitation totals during the growing season have been recorded during the period 1989-2009 (5). Particularly strong droughts were in 1990-1994, 2000, 2002, 2003 and 2007

An increase in winter precipitation (snow) between 1951 and 2008 has been recorded in Slovakia in both the north and south regions, and this trend could continue in the future (5).

In central and western Europe, significant increasing precipitation trends over the 20th century dominate in winter for both average precipitation intensity and moderately strong events. Simultaneously, the length of dry spells generally increased insignificantly (2).

Heat wave and cold wave changes until now

In the Carpathian Region (encompassing Croatia, Hungary, Slovakia, Czech Republic, Poland, Ukraine, Romania and Serbia), heat wave events have become more frequent, longer, more severe and intense over the period 1961 - 2010, in particular in summer in the Hungarian Plain and in Southern Romania (6). Cold wave frequency, average duration, severity, and intensity over this period, on the other hand, generally decreased in every season except autumn. In this study, a heat wave was defined as at least five consecutive days with daily maximum temperature above the long-term 90th percentile of daily maximum temperatures. Similarly, a cold wave was defined as at least five consecutive days with daily minimum temperatures below the long-term 10th percentile of daily minimum temperatures (6).

The trend analysis shows a general tendency to more frequent, longer, more severe and more intense heat wave events in every season in the entire Carpathian Region. On the other hand, the cold waves show a general tendency to less frequent, shorter, less severe, and less intense events (6).

The Carpathian Region and the Mediterranean area are the two European hotspots showing a drought frequency, duration, and severity increase in the past decades and in particular from 1990 onwards (7). When drought effects are exacerbated by heat waves or vice versa, such combination may cause devastating effects, as it happened in summer 2003 in Central Europe (8). 

Air temperature changes in the 21st century

Results from model calculations show a temperature increase in Slovakia in 2081-2100 compared to 1971-1990 of 3.8⁰C per year. For March and November respective increases of 5.2⁰C and 3.3⁰C are projected (1). If no action is taken to reduce greenhouse gas emissions, annual mean temperature in central Europe may increase up to 4-4.5°C in continental regions by the end of the 21st century (4).

It is clear that potential evaporation in the summer will significantly increase which will result in a decrease of soil humidity in southern Slovakia and a decrease of runoff in mountain areas. A dramatic increase of number of very warm days is expected (1).

In past decades heat waves (series of days with mean daily temperature above 24°C) were recorded sporadically in Slovakia (about 6 days a year). The number of such days has already increased twice or three times. In the south of the country, a further increase is expected up to about 45 such days a year by the end of this century (5).

By the end of the twenty first century, countries in central Europe will experience the same number of hot days as are currently experienced in southern Europe (3).

Heat wave changes in the 21st century

Heat waves in Central Europe 

In the last three decades of the previous century Central Europe has experienced 22 heat waves. Future changes in the frequency of occurrence of these heat waves were studied for this part of Europe, that includes most of Germany, the Czech Republic, Slovakia, the Southwest of Poland, Northern Austria and Hungary (9). In this study a heat wave is defined by at least three consecutive hot days. A hot day occurs when on average maximum daily temperature over Central Europe exceeds the 90th percentile of the distribution of daily maximum summer temperatures for the period 1970 - 1999. This value of the 90th percentile for this historical period is also kept as the reference for quantifying future hot days and heat waves.

Compared to this historic period, the frequency of heat waves is projected to increase by a factor 2 in the near future (2020 - 2049). For the late twenty-first century (2070 - 2099), the projected frequency increase of heat waves depends on the rate of climate change: under a high-end scenario of climate change (RCP 8.5), 3-4 heat waves per summer are projected, compared to about two heat waves under a moderate scenario of climate change (RCP 4.5). These projections are based on a large number of combinations of global and regional climate models (9).

The 1994 heat wave is found to be the most distinctive during the 1970 - 1999 period. It lasted 16 days and was associated with large excess mortality in the Czech Republic (10), Poland (11) and other Central European countries. This heat wave has been ranked as the most severe in Central Europe over the whole 1950 - 2012 period (12). Such extraordinary heat waves will probably still be rather rare in the near future. At the end of this century, however, at least one event per decade similar to the 1994 heat wave is projected for Central Europe (9). 

Precipitation changes in the 21st century

Climate change scenarios project the prolongation of drought periods and the increase in precipitation totals during short periods with cyclonal weather in summer. It is supposed that the totals of extremely heavy precipitation events (repeating more rarely than once per 50 years) will be higher than in past decades by 25-50%. Presumably the highest precipitation totals will exceed 150 mm every year and 400 mm once per 50 years (5).

Precipitation totals are expected to increase up to 30% in the north of Slovakia and in highlands by the end of the century (5).

The occurrence of snow and snow cover will not be endangered by the projected 4°C temperature increase by the end of this century at the altitude over 1200 m. Peak snow cover (new snow cover and total snow cover) can be expected more often. The risk of avalanches will certainly increase in Slovakia (5). 

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Slovakia.

1. Ministry of Environment of the Slovak Republic (2005)
2. Moberg and Jones (2005)
3. Beniston et al. (2007)
4. Commission of the European Communities (2007)
5. Ministry of the Environment of the Slovak Republic and the Slovak Hydrometeorological Institute (2009)
6. Spinoni et al. (2015)
7. Spinoni et al. (2013), in: Spinoni et al. (2015)
8. Fink et al. (2004); Ciais et al. (2005), both in: Spinoni et al. (2015)
9. Lhotka et al. (2018)
10. Kyselý and Huth (2004), in: Lhotka et al. (2018)
11. Kuchcik (2001), in: Lhotka et al. (2018)
12. Lhotka and Kyselý (2015a), in: Lhotka et al. (2018)