Climate change Italy
Italy is formally divided into four climates:
- Alpine climate, dominant in the Alps and northern and central Apennines, characterized by night and winter low temperatures and moist summer;
- Mediterranean climate, on the islands and in southern Italy, characterized by mild temperatures and moist winter;
- Peninsular climate, in the central part of the peninsula, characterized by mild temperatures along the coast and in the prompt hinterland (in the middle where the altitude is high there is an alpine climate), moist in spring and autumn;
- Po valley climate, with low temperatures in the winter, high in the summer, moist in spring and autumn.
Air temperature changes until now
Mean temperature trends
Different estimates of mean temperature trend in Italy over more than 100 years have been reported: a total temperature increase from 1850–1899 to 2001–2005 of 0.76°C (± 0.19°C) (1), and a temperature increase from 1865 to 2003 of 1.0 ±0.1°C per century (2). According to the latter there are no significant differences (generally not higher than 0.3°C/century) between seasons and regions. These results also show that minimum temperature has increased more than maximum temperature (particularly in the north) (2). Similar temperature trends for all seasons were confirmed for Sicily (20).
An estimate of the mean temperature trends in Italy from 1961 to 2006 shows a negative trend for the mean temperature from 1961 to 1980, with a decrease over this time period of about 0.6°C, followed by a positive trend from 1980 to 2006, with a mean increase of +1.54°C (3). The net variation from 1961 to 2006 is slightly less than +1°C, almost equal to 2°C/century. Similar results were reported for the period 1961 to 2011 (23): a change point in 1977, with non-significant “cooling” trends characterizing the sub-period 1961–1977, while significant “warming” trends were identified over the period 1978–2011.
For the period 1961 – 2011, significant trends have been identified for summer days, tropical nights, heat waves, and minimum and maximum temperature extremes at most stations, with warming trends more pronounced in summer and spring and weaker in winter and autumn. From 1978 to 2011, Italy experienced on the average the following variations per decade: an increase of four to five tropical nights and summer days, a decrease of frost days of the same order, an increase of 3–4 % of warm days and nights, and a decrease of 1–1.5 % of cold days and nights. In the same period, heat waves have increased on the average at the rate of 7.5 days per decade (23).
The observed mean temperature increase recorded during the last decades in Italy, as well as in the Mediterranean and in Europe, is higher than the global mean (4).
Maximum and minimum temperature trend
With regard to the trend of maximum and minimum temperature, in the recent years the situation is reversed compared to 1865-2003 data. As a matter of fact the maximum temperature has increased more than minimum and, as a consequence, also the daily temperature range. Also the summer heat waves have increased both in length and in intensity. 2003 has been not only the hottest year ever recorded during the last 200 years, but has shown the strongest and prolonged heat waves. On the other hand, the winter cold spells have decreased, especially in frequency (4).
In the period 1961-1990 two trends may be distinguished. In the first, from 1961 till 1981, the number of tropical night’s (minimum temperature greater than 20°C) has decreased, while from 1981 till 2006 it has increased at a faster rate. In the whole period, a net increase of about 50% of the number of tropical nights is estimated. Besides, from 1961 till 1978, the number of summer days (maximum temperature greater than 25°C) has decreased, while from 1978 till 2006 it has increased. In the whole period, a net increase of about 14% of the number of summer days is estimated. A decrease of about 0.2 frost days per year from 1961 to 2006 is estimated, corresponding to an average reduction of about 20% (4).
For southern Italy, for the 1951–2010 period, an increase of the number of warm days, warm nights and tropical nights, and a decrease of the number of (very) cold nights, cold days, frost days and ice days was observed, especially because of an increase in temperature after 1971 (22).
Alpine temperature trend
As far as alpine and mountain environments are concerned, on the basis of data collected at altitude by weather stations located on the Italian, Swiss, and Austrian sides of the Alps, the average temperature increase rate over the alpine chain during the last century has been between 1.5 and 2°C, the largest part of this increase dating from after 1980. Changes have also been observed in snowfall, and in frequency of snow slides and avalanches (4).
Recent research suggests that there is a similar air temperature trend in the Alps at low and very high altitudes over the last 100 years. Temperature profiles have been analyzed from boreholes drilled at three different sites between 4240 and 4300 m above sea level in the Mont Blanc area (French Alps). A mean warming rate of 0.14 °C/decade between 1900 and 2004 was found. This is similar to the observed regional low altitude trend in the north-western Alps, suggesting that air temperature trends are not altitude dependent (17).
Precipitation changes until now
Total precipitation trend
Differently from temperature, the accumulated precipitations show neither pronounced nor univocal trends on the Italian territory. An analysis of weather stations data shows a significant reduction trend for precipitation for only 2 out of 6 studied regions (central Italy and south-east Italy: -10 ± 3%/century and –8 ± 5%/century, respectively) (4). A decrease in precipitation between 1951 and 1996 has been reported of 14% throughout the country but most significantly in the centre and in the south (5); these results were confirmed for the southern Basilicata region for the period 1951-2010 (19). Reductions of precipitation in some areas during the last century up to 20% have been reported (6).
Precipitation intensity trend
The results show an overall reduction trend of the number of low intensity events and a concentration of precipitation in events with higher mean intensity compared to the past (2,16). The total number of rainy days has decreased, especially in the last 50 years: the decrease is about 6 days/century in the north and 14 days/century in the central part and in the south. The overall trend, for all the Italian regions, is in the direction of an increase of precipitation intensity and towards a decrease of their duration. Also the dry spells are on the increase and their persistence is higher in winter in the north and in summer in the south (2).
Precipitation intensity increase is due to a decrease in the contribution of low precipitation categories to total precipitation and to an increase in that of higher categories corresponding to heavy precipitation events (2). For the entire Mediterranean during the second half of the previous century extreme daily rainfall increased in spite of the fact that total rainfall generally decreased. For instance, torrential rainfall exceeding 128 mm/d contributes 4–5% of the total Italy rainfall in the 1990s compared to only 1% in the 1950s; an increase by a factor of 4 (7).
In Europe a substantial increase in the intensity of daily precipitation events has been found (8). This holds even for areas with a decrease in mean precipitation, such as central Europe and the Mediterranean region during summer. It is associated with both changes in the number of wet days (decreasing for southern Europe) and changes in the amount of precipitation on wet days. The combined effects of warmer temperatures and reduced mean summer precipitation would enhance the occurrence of heat waves and droughts.
The tendency of a decrease in the number of rainy days and an increase in intensity is not a peculiarity of recent decades but it has persisted since the end of the 19th century (2). … For the last 50 years, the observed climate changes (in particular the rainy days decrease) could be linked to some changes in atmospheric circulation. … An increase in the frequency of westerlies in relation to the strengthening of the NAO has been observed for the last decade. This kind of variation in the European pressure patterns can justify an increase in precipitation at the higher latitudes (i.e. north of the Alps) and a decrease in the Mediterranean region, due to a northward shift of the jet-stream, especially in winter. The positive trend of the pressure over the Mediterranean also agrees with the hypothesis of an increase of the number and the persistence of anticyclones in this region (2).
Glacier changes until now
Scientists consider glaciers to be among the best natural indicators of climate change and, therefore, monitor them closely. Rapidly shrinking glacier areas, spectacular tongue retreats, and increasing mass losses are clear signs of the atmospheric warming observed in the Alps during the last 150 years. The Alps could lose up to 80% of their glacier cover by the end of this century, if summer air temperatures rise by 3°C. If temperature increases by 5°C, the Alps would become almost completely ice-free by 2100 (9).
In the 1970s, about 5,150 Alpine glaciers covered a total area of 2,909 square kilometres. This represented a loss of about 35% of glacial area from 1850 to that time. Accelerated loss of ice cover since then has resulted, today, in a total loss of 50% of the 1850 area, culminating in a volume loss of 5 to 10% of the remaining ice during the extraordinary warm year of 2003 (4).
Air temperature changes in the 21st century
Temperature rise in Europe
In Europe, extreme temperatures will occur more frequently. The yearly maximum temperature is expected to increase much more in southern and central Europe than in northern Europe (10). A large increase is also expected for yearly minimum temperature in most of Europe, which in many locations exceeds the average winter warming by a factor of two to three. Much of the warming in winter is connected to higher temperatures on cold days, which indicates a decrease in winter temperature variability. An increase in the lowest winter temperatures, even if quite large, would primarily mean that current cold extremes would decrease. On the other hand, a large increase in the highest summer temperatures would expose Europeans to unprecedented high temperatures.
Temperature rise in the Mediterranean
Similar to northern Europe, the Mediterranean region will warm at a rate of between 0.1 and 0.4ºC/decade. The largest temperature increases are projected for southern Europe in the summer months (0.2-0.6⁰C per decade) (11).
Projections of climate change (IPCC SRES A1B emissions scenario) suggest an annual average temperature increase in southern Europe in the period from 1980-1999 to 2080-2099 in between 2.0 and 5.1°C, with a median value of 3.5°C. In the regions bordering the Mediterranean, Italy included, the foreseen warming is greater in the summer (4). The increase of averaged seasonal minimum and maximum temperature has been projected for Northern Italy for the periods 2021–2050 (using 8 GCMs) and 2070–2099 (using 7 GCMs) with respect to 1961–1990. This was done for the IPCC SRES A1B emission scenario. The results show a projected mean seasonal minimum and maximum temperature increase around 1.5–2°C over Northern Italy for 2021–2050 (with possible higher increase up to 3°C for the summer, autumn and spring). For the period 2070–2099 the projected mean seasonal minimum and maximum temperature increase was around 2.5°C during winter, spring and autumn; during summer season, both mean seasonal minimum and maximum temperature may increase by 3.5–4°C with respect to present climate 1961–1990 (21).
Using different emissions scenarios, the range of the average temperatures increase, foreseen from different models, may vary sensibly. For the IPCC SRES B1 and A2 scenarios for example, which are those placed at the minimum and the maximum of CO2 emission range foreseen at 2100, the width of the range of the average temperatures increase, foreseen by the models, go from 3.8°C (2,7 - 6.5°C) to about 9-10°C. The average of the distribution remains included between +4 and +5°C (4).
According to analyses based on the IPCC SRES A2 and B2 emission scenarios, the time that global temperature is expected to reach 2⁰C above pre-industrial levels is in the thirty-year period (2031-2060) (12). A global temperature rise of 2°C is likely to lead to a corresponding warming of 1-3°C in the Mediterranean region. The warming is likely to be higher inland than along the coast. The largest increase in temperature is expected to take place in the summer, when extremely hot days and heat waves are expected to increase substantially, especially in inland and southern Mediterranean locations (12).
Concerning the variability of the average temperature, most models foresee an increase of the interannual standard deviation of summer temperature both in northern Europe and in the Mediterranean. In the winter months the models indicate, by contrast, a reduction of the variability of the average temperature. … Other significant results concern the forecast of an important decrease of the number of cold days and an increase of the heat waves duration index, defined as the maximum number of consecutive days with maximum temperature more than 5°C higher than the normal value (4).
The global 2°C temperature rise is expected to be seasonally and spatially translated in the Mediterranean region by (12):
- Largest increase in summer, and inland: Tmean by 4°C and Tmax by 5°C, on average;
- Second largest increase in fall: 2-3°C everywhere;
- Spring temperatures could rise by about 2°C;
- Winter and spring temperatures could rise less than 2°C;
- Although less pronounced, thanks to the sea, the rise in coastal region temperature is expected to be in the 1-2°C range on average, and a bit more than 2°C in summer for Tmax;
- Tmax is expected to rise more than Tmin.
The expected higher rise of Tmax than Tmin (heat stress intensification) is due to preferential warming of the hot tail of the daily temperature distribution. This preferential warming of the hot tail is dictated in large part by a surface moisture feedback, with areas of greatest warm-season drying showing the greatest increases in hot temperature extremes (13).
Number of summer days
In 2031-2060 compared with 1961-1990 the increase in the number of summer days, defined as the number of days when Tmax exceeds 25⁰C, is from 2 to 6 weeks (12):
- Large increases are found in the central Mediterranean region (i.e. Crete, Peloponnese, South Greece, Sicily), North Adriatic, and inland (within Maghreb, Spain, Turkey, South of France and the Balkans). In this group, the largest increase seems to occur in Crete with an additional 7 weeks of summer and the smallest in the Maghreb with an additional 3-5 weeks of summer.
- On the other hand, the coastal regions of the western Mediterranean, the Black Sea and the Middle East is expected to have the smallest increases with only 2-3 additional weeks of summer.
- It is expected that there will be, on average, one additional summer month everywhere inland, as well as in the central Mediterranean coastal region, and about half a month on all other coastal regions except the central Mediterranean region.
Number of hot days and tropical nights
The pattern in the number of hot days, defined as the number of days with Tmax> 30 °C is somewhat different from the pattern of the number of summer days. In 2031-2060 compared with 1961-1990 the increase is from 2 weeks along the coast to 5-6 weeks inland (within Spain, Turkey, South of France, the Balkans and in the Maghreb) indicating the role the Mediterranean Sea exerts in preventing too hot days (12).
In 2031-2060 compared with 1961-1990 the number of tropical nights, defined as the number of nights with Tmin > 20°C increases by about a month almost everywhere. Only regions well within land are expected to keep their night fresh, with only 1-2 weeks per year of additional tropical nights (12).
Number of hot heat waves
The changes in the number of heat waves in 2031-2060 compared with 1961-1990, defined as the change in the number of weeks per year with temperatures exceeding 35⁰C, are about the same for both scenarios (A2 and B2). Continental areas in Spain, the Middle East, Turkey, the Balkans, North Africa and North Italy are expected to experience an increase of 3-5 weeks of heat wave days. Areas under the moderating influence of the Mediterranean sea are likely to see very small or no changes. Such areas are all the islands, South Italy, and Peloponese. The sole exception occurs in the islands in the North Aegean Sea, which are expected to experience more heat waves (4 weeks more) in the future period (12).
Number of frost and ice days
For a part of Northern Italy (Emilia-Romagna) changes in the number of frost days (lowest temperature < 0°C) and winter ice days (highest temperature < 0°C) have been projected for the period 2070–2099 (using 7 GCMs and the IPCC SRES A1B emission scenario) with respect to 1961–1990. The projections show a decrease up to 35 days in the number of frost days and up to 6 days in the number of ice days in the winter by the end of the century (21).
Precipitation changes in the 21st century
Average annual precipitation
Projections of climate change (IPCC SRES A1B emissions scenario) suggest a decrease of average annual precipitation in southern Europe from 1980–1999 to 2080–2099 of between 4 and 27%. A more pronounced decrease is expected in the summer season. … Using different emission scenarios, the range of precipitation change shown by the models increases with respect to the A1B scenario (4).
Under the A2 scenario, a drop in precipitation seems to be the dominant feature of the future precipitation regime (2031-2060 compared with 1961-1990) (12):
- 0-10% drop in precipitation in the northern part;
- 10-20% drop in precipitation in the southern part including Spain.
Under the B2 scenario:
- both increases and decreases in total yearly rainfall are expected for the northern part;
- a 0-20% drop is evident in the southern part.
Interannual precipitation variability
Projections point to more precipitation in the winter and less in summer over the region as a whole, while mean annual precipitation is expected to decline south of 45°N. The general tendency would be that northern parts of the Mediterranean would become wetter and the southern parts drier, thus amplifying current rainfall differences and water scarcity (6).
It has been concluded that the future European summer climate would experience a pronounced increase in year-to-year variability and thus a higher incidence of heat waves and droughts (14). It has also been estimated that Mediterranean droughts would start earlier in the year and last longer (15). Although only the eastern Mediterranean currently has a regularly recurring dry period, the rest of the Mediterranean and even much of Eastern Europe may also experience such periods by the late 21st century.
Rainfall increases in the northern Mediterranean, particularly in winter. However, under both A2 and B2 scenarios precipitation decreases substantially in the summer in both the north and the south (6,12). In the south, the reduction in precipitation extends year round.
Longer droughts are shown to be common, and are accompanied by shifts in timing. In terms of extremes, the number of dry days (daily precipitation amount less than 0.5 mm) is shown to increase while the number of wet and very wet days remains unchanged. This can imply that when it rains it will rain more intensely and strongly, especially at certain locations in the northern Mediterranean (Italy, Western Greece, South of France, and the northwestern part of the Iberian Peninsula). On the contrary, rainfall is likely to become less intense over the southern Mediterranean (12).
Snow cover changes in the 21st century
An increase of the average temperature of 4°C in the Alps, as expected on average by the models in the A2 scenario, would reduce the duration of snow cover by 50% at the altitude of 2000 m and by 95% under 1000 m a.s.l (4).
Changes in mean winter snow water equivalent (SWE), the seasonal evolution of snow cover, and the duration of the continuous snow cover season in the European Alps have been assessed from an ensemble of regional climate model (RCM) experiments under the IPCC SRES A1B emission scenario. The assessment was carried out for the periods 2020–2049 and 2070–2099, compared with the control period 1971–2000. The strongest relative reduction in winter mean SWE was found below 1,500 m, amounting to 40–80 % by mid century relative to 1971–2000 and depending upon the model considered. At higher elevations the decrease of mean winter SWE is less pronounced but still a robust feature. For instance, at elevations of 2,000–2,500 m, SWE reductions amount to 10–60 % by mid century and to 30–80 % by the end of the century (18).
The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Italy.
- Alley et al. (2007), in WHO (2007)
- Brunetti et al. (2006a, 2006b), in: Ministry for the Environment, Land and Sea of Italy (2007)
- Toreti and Desiato (2007a), in: Ministry for the Environment, Land and Sea of Italy (2007)
- Ministry for the Environment, Land and Sea of Italy (2007)
- WHO (2007)
- Eisenreich (2005)
- Alpert et al. (2002), in: Ministry for the Environment, Land and Sea of Italy (2007)
- Christensen and Christensen (2003); Giorgi et al. (2004); Kjellström (2004), all in: Ministry for the Environment, Land and Sea of Italy (2007)
- Zemp (2006), in: Ministry for the Environment, Land and Sea of Italy (2007)
- Räisänen et al. (2004); Kjellström et al. (2004), both in: WHO (2007)
- Haas (2002), in: Eisenreich (2005)
- Giannakopoulos et al. (2005)
- Diffenbaugh et al. (2007)
- Schaer et al. (2004), in: Ministry for the Environment, Land and Sea of Italy (2007)
- Beniston et al. (2004), in: Ministry for the Environment, Land and Sea of Italy (2007)
- Todeschini (2012)
- Gilbert and Vincent (2013)
- Steger et al. (2013)
- Piccarreta et al. (2013)
- Viola et al. (2014)
- Tomozeiu et al. (2014)
- Piccarreta et al. (2015)
- Fioravanti et al. (2016)