Assumptions about future trends

12.3.1 Climate projections

123.1.1 Mean climate

Results presented here and in the following sections are for the period 2070 to 2099 and are mostly based on the IPCC Special Report on Emissions Scenarios (SRES: Nakicenovic and Swart, 2000; see also Section 12.3.2) using the climate normal period (1961 to 1990) as a baseline.

Europe undergoes a warming in all seasons in both the SRES A2 and B2 emissions scenarios (A2: 2.5 to 5.5°C, B2: 1 to 4°C; the range of change is due to different climate modelling results). The warming is greatest over eastern Europe in winter (December to February: DJF) and over western and southern Europe in summer (June to August: JJA) (Giorgi et al., 2004). Results using two regional climate models under the PRUDENCE project (Christensen and Christensen, 2007) showed a larger warming in winter than in summer in northern Europe and the reverse in southern and central Europe. A very large increase in summer temperatures occurs in the southwestern parts of Europe, exceeding 6°C in parts of France and the Iberian Peninsula (Kjellstrom, 2004; Raisanen et al., 2004; Christensen and Christensen, 2006; Good et al., 2006).

Generally for all scenarios, mean annual precipitation increases in northern Europe and decreases further south, whilst the change in seasonal precipitation varies substantially from season to season and across regions in response to changes in large-scale circulation and water vapour loading. Raisanen et al. (2004) identified an increase in winter precipitation in northern and central Europe. Likewise, Giorgi et al. (2004) found that increased Atlantic cyclonic activity in DJF leads to enhanced precipitation (up to 15-30%) over much of western, northern and central Europe. Precipitation during this period decreases over Mediterranean Europe in response to increased anticyclonic circulation. Raisanen et al. (2004) found that summer precipitation decreases substantially (in some areas up to 70% in scenario A2) in southern and central Europe, and to a smaller degree in northern Europe up to central Scandinavia. Giorgi et al. (2004) identified enhanced anticyclonic circulation in JJA over the north-eastern Atlantic, which induces a ridge over western Europe and a trough over eastern Europe. This blocking structure deflects storms northward, causing a substantial and widespread decrease in precipitation (up to 30-45%) over the Mediterranean Basin as well as over western and central Europe. Both the winter and summer changes were found to be statistically significant (very high confidence) over large areas of the regional modelling domain. Relatively small precipitation changes were found for spring and autumn (Kjellstrom, 2004; Raisanen et al., 2004).

Change in mean wind speed is highly sensitive to the differences in large-scale circulation that can result between different global models (Raisanen et al., 2004). From regional simulations based on ECHAM4 and the A2 scenario, mean annual wind speed increases over northern Europe by about 8% and decreases over Mediterranean Europe (Raisanen et al., 2004; Pryor et al., 2005). The increase for northern Europe is largest in winter and early spring, when the increase in the average north-south pressure gradient is largest. Indeed, the simulation of DJF mean pressure indicates an increase in average westerly flow over northern Europe when the ECHAM4 global model is used, but a slight decrease when the HadAM3H model (Gordon et al., 2000) is used. For France and central Europe, all four of the simulations documented by Räisänen et al. (2004) indicate a slight increase in mean wind speeds in winter and some decrease in spring and autumn. None of the reported simulations show significant change during summer for northern Europe.

12.3.12 Extreme events

The yearly maximum temperature is expected to increase much more in southern and central Europe than in northern Europe (Räisänen et al., 2004; Kjellström et al., 2007). Kjellström (2004) shows that, in summer, the warming of large parts of central, southern and eastern Europe may be more closely connected to higher temperatures on warm days than to a general warming. A large increase is also expected for yearly minimum temperature across most of Europe, which at 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, although large, would primarily mean that current cold extremes would decrease. In contrast, a large increase in the highest summer temperatures would expose Europeans to unprecedented high temperatures.

Christensen and Christensen (2003), Giorgi et al. (2004) and Kjellström (2004) all found a substantial increase in the intensity of daily precipitation events. This holds even for areas with a decrease in mean precipitation, such as central Europe and the Mediterranean. Impact over the Mediterranean region during summer is not clear due to the strong convective rainfall component and its great spatial variability (Llasat, 2001). Palmer and Räisänen (2002) estimate that the probability of extreme winter precipitation exceeding two standard deviations above normal would increase by a factor of five over parts of the UK and northern Europe, while Ekström et al. (2005) have found a 10% increase in short duration (1 to 2 days) precipitation events across the UK. Lapin and Hlavcova (2003) found an increase in short duration (1 to 5 days) summer rainfall events in Slovakia of up to 40% for a 3.5°C summer warming.

The combined effects of warmer temperatures and reduced mean summer precipitation would enhance the occurrence of heatwaves and droughts. Schär et al. (2004) conclude that the future European summer climate would experience a pronounced increase in year-to-year variability and thus a higher incidence of heatwaves and droughts. Beniston et al. (2007) estimated that countries in central Europe would experience the same number of hot days as currently occur in southern Europe and that Mediterranean droughts would start earlier in the year and last longer. The regions most affected could be the southern Iberian Peninsula, the Alps, the eastern Adriatic seaboard, and southern Greece. The Mediterranean and even much of eastern Europe may experience an increase in dry periods by the late 21st century (Polemio and Casarano, 2004). According to Good et al. (2006), the longest yearly dry spell could increase by as much as 50%, especially over France and central Europe. However, there is some recent evidence (Lenderink et al., 2007) that these projections for droughts and heatwaves may be slightly over-estimated due to the parameterisation of soil moisture (too small soil storage capacity resulting in soil drying out too easily) in regional climate models.

Regarding extreme winds, Rockel and Woth (2007) and Leckebusch and Ulbrich (2004) found an increase in extreme wind speeds for western and central Europe, although the changes were not statistically significant for all months of the year. Beniston et al. (2007) found that extreme wind speeds increased for the area between 45°N and 55°N, except over and south of the Alps. Woth et al. (2005) and Beniston et al. (2007) conclude that this could generate more North Sea storms leading to increases in storm surges along the North Sea coast, especially in the Netherlands, Germany and Denmark.

12.3.2 Non-climate trends

The European population is expected to decline by about 8% over the period from 2000 to 2030 (UN, 2004). The relative overall stability of the population of Europe is due to population growth in western Europe alone, mainly from immigration (Sardon, 2004). Presently, CEE and Russia have a surplus of deaths over births, with the balance of migration being positive only in Russia. Fertility rates vary considerably across the continent, from 1.10 children per woman in Ukraine to 1.97 in Ireland. There is a general decline in old-age mortality in most European countries (Janssen et al., 2004), although there has been a reduction in life expectancy in Russia during the 1990s. The low birth rate and increase in duration of life lead to an overall older population. The proportion of the population over 65 years of age in the EU15 is expected to increase from 16% in 2000 to 23% in 2030, which will likely affect vulnerability in recreational (see Section 12.4.9) and health aspects (see Section 12.4.11).

The SRES scenarios (see Chapter 2 Section 2.4.6) for socioeconomic development have been adapted to European conditions (Parry, 2000; Holman et al., 2005; Abildtrup et al., 2006). Electricity consumption in the EU25 is projected to continue growing twice as fast as the increase in total energy consumption (EEA, 2006a), primarily due to higher comfort levels and larger dwellings increasing demand for space heating and cooling, which will have consequences for electricity demand during summer (see Section 12.4.8.1).

Assumptions about future European land use and the environmental impact of human activities depend greatly on the development and adoption of new technologies. For the SRES scenarios it has been estimated that increases in crop productivity relative to 2000 could range between 25 and 163% depending on the time slice (2020 to 2080) and scenario (Ewert et al., 2005). These increases were found to be smallest for the B2 and highest for the A1FI scenario. Temporally and spatially explicit future scenarios of European land use have been developed for the four core SRES scenarios (Schröter et al., 2005; Rounsevell et al., 2006). These scenarios show large declines in agricultural land area, resulting primarily from the assumptions about technological development and its effect on crop yield (Rounsevell et al., 2005), although climate change may also play a role (see Section 12.5.7). The expansion of urban area is similar between the scenarios, and forested areas also increase in all scenarios (Schröter et al., 2005). The scenarios showed decreases in European cropland for 2080 of 28 to 47% and decreases in grassland of 6 to 58% (Rounsevell et al., 2005). This decline in agricultural area will mean that land resources will be available for other uses such as biofuel production and nature reserves. Over the shorter term (up to 2030) changes in agricultural land area may be small (van Meijl et al., 2006).

0 0

Post a comment