Expected climate change for Cesena pilot area
Expected climate change presented in this short document is the summary of the ADRIADAPT D.3.3.1 document – Climate change projections for Cesena with special emphasis on severe impacting events. For more information on the data used, processing and analysis methods, graphical representations of the results and conclusions, we advise to look at this document.
1.1 Dynamically downscaled
In this section, we present future climate change of temperature and precipitation related indices, surface relative humidity and extra rare perceived temperature projections for Cesena. All indices are calculated from the four available regional climate models for the model point representing the location of Cesena. Data set is obtained by interpolation of data from neighbouring points. Data are presented as follows:
- Climate change diagram of an individual index in seasons: DJF standing for the months of the winter season, MAM for the months in spring, JJA for the summer months, and SON representing the autumn months. Data is presented furthermore and on annual basis for four future periods: 2021-2040, 2041-2060, 2061-2080 and 2081-2100 and for two emission scenarios: a moderate one called also stabilization scenario (RCP4.5) simulating a future world where considerable efforts have been put into mitigation policies and a high-emissions climate scenario (RCP8.5, often called pessimistic climate scenario) which simulates a future world without climate mitigation policies. We calculated indices representing the difference between future and present climate climate (called also future anomalies or changes). Reference period is 1985-2006 and a star markes such values for which changes are statistically significant.
- Time series of the future anomaly (or changes) of an individual index for the winter (DJF)and summer season (JJA) for RCP4.5 and RCP8.5 emission scenarios. Anomaly is calculated concerning the reference period and shown for the individual models, the mean and the 5-year average. Statistical trend test is applied to the ensemble mean (for 95 % confidence level). A significant trend is marked with a star (ns if not significant).
1.2 Statistically downscaled
In this section, we present future climate changes of temperature and precipitation related indices for Cesena, simulated by the statistical downscaling techniques set-up on the observed local data/observed large scale circulation patterns and then applied to the future large-scale circulation patterns simulated by four global climate models (GCMs). The results are presented as follows:
- Climate change diagram of an individual index for each season and on annual basis for four considered future periods: 2021-2040, 2041-2060, 2061-2080, 2081-2100 and the two emission scenarios (RCP4.5 and RCP8.5). Anomalies or future changes are calculated as a difference between future and reference period (present climate) for temperature indices and some intense precipitation indices, and as their relative differences (expressed in %) for precipitation. The reference period (noted as Ref. mean or obs.) is 1986-2005, the climate observed value is the one registered at the meteorological station, while the values for the different periods in the future are shown for the different downscaled climate models as well as for the ensemble mean of those models (ENSMEAN). A statistical test is applied to test the significance of future climate change with respect to the present climate value. The results considered as significant are marked by a star.
- Time-series of a future anomaly of an individual index for winter and summer and for two emission scenarios; the anomaly is calculated with respect to the reference period and shown for individual models, the ensemble mean and 5-year moving average. A statistical trend test is applied to the ensemble mean and significant value is marked with a star (n.s. if not significant).
2 Temperature related data
2.1 Results from dynamical downscaling (DD)
2.1.1 Averaged 2 meter air temperature
Averaged temperature change in Cesena shows increase in all seasons and on annual scale, for all future periods (exception is in winter for one model realisation in first period). Although each model gives different amplitude of change, in ensemble mean the change is highest during summer or autumn and the smallest in winter and spring for moderate climate scenario. The temperature increase is more pronounced towards the end of the century whit an increase of mean temperature of 1.5°C in winter and spring and 2.0°C in summer. On annual scale for moderate scenario temperature increase is for 1.7°C. The amplitude of temperature change is more pronounced for high-emissions climate scenario, reaching on annual scale 3.7°C at the end of 21st century for ensemble mean. The linear trend of temperature anomaly (Figure 1) in the future shows an increase which is statistically significant for both considered seasons and both scenarios; in winter is 0.20°C per decade for the moderate climate scenario and 0.54°C per decade for the high-emissions scenario; in summer is 0.16°C per decade for the moderate climate scenario and 0.49°C per decade for the high-emissions scenario.
Figure 1: Variability of future 2m air temperature anomaly (in °C) in Cesena for 2021-2100 obtained by dynamically downscaling for winter (DJF) and summer (JJA) and two emission scenarios, moderate (RCP4.5) and high-emissions (RCP8.5): individual models are in grey, the ensemble mean in red, 5-year moving average in black. Significant trend is marked with star (ns if not significant).
2.1.2 Extreme high temperature
Extreme high temperatures (defined as 99th percentile of 2m air temperature) in Cesena are projected to increase in all seasons and on annual scale, for all future periods.
At annual level, an increase of 2.4°C is expected for moderate scenario (RCP4.5) and of 4.6°C for high-emissions scenario (RCP8.5), at the end of the 21st century. At seasonal level, autumn is the season with higher changes for RCP4.5 (up to 2.6°C ) and for RCP8.5 (up to 5.4°C) during 2081-2100 period.
2.1.3 Extreme high maximum temperature
The change of extremely high temperatures of 2m maximum air temperature in Cesena(defined as 99th percentile of 2m maximum air temperature), is increasing from first to last future periods with the different amplitudes for each model and season. At the end of the century, the change of extreme high maximum temperature ranges from 1.9°C in winter to 2.9°C in spring, 2.2°C on the annual scale for moderate climate scenario. The amplitude of change is more pronounced for pessimistic climate scenario and is between 3.4°C in winter and 5.0°C in autumn, 4.3°C for annual change at the end of 21st century.
2.1.4 Extreme rare high temperature
Future change of 99.9th percentile of 2m air temperatures (extreme rare high temperature) in Cesena is increasing towards the end of the century with the different amplitudes for each model. A slightly negative change appears for some seasons and some models for the periods until 2060, but the average change is positive for all periods. At the end of century increase is on annual scale 2.2°C for moderate climate scenario and 4.3°C for pessimistic climate scenario.
2.1.5 Extreme rare high maximum temperature
Analysing the future change of extreme rare high maximum temperature (defined as 99.9th percentile of 2m maximum air temperature) we came to the same conclusion. Some models show for some time slices small negative change, but in general, the ensemble mean for all seasons and annual change are positive ranging up to 6.2°C in spring at the end of 21st century within the pessimistic climate scenario.
2.2 Results from statistical downscaling (SD)
2.2.1 Seasonal minimum and maximum temperature
The future projections show possible increases in seasonal minimum and maximum temperature from first to last future period and, both emission scenarios. Following the moderate scenario, we expect an increase in annual minimum temperature of 1.0°C during the first period (2021-2040) and up to 2.3°C at the end of the century. The projected increase in annual minimum temperature is higher for high-emissions climate scenario, especially for the last two future periods, when the simulations show changes up to 4.7°C. . Analysing in details the seasonal projected changes of minimum temperature, summer season shows a higher magnitude of changes, up to 5.1°C in high-emissions scenario towards the end of the century. The long term variability of projected changes represented in Figure 2 shows positive and significant trends, more intense for pessimistic climate scenario and especially in summer, about 0.6°C/decade.
As regards maximum temperature, following the moderate RCP4.5 scenario we expect an increase in annual maximum temperature between 1.5°C during the first period (2021-2050) and up to 3.3°C going to the end of century (2081-2100). The projected increase is higher for RCP8.5, especially for 2061-2080 and 2081-2100 when the simulations show changes in annual maximum temperature about 4.9°C and 6.6°C, respectively.
Seasonally, the projected changes of maximum temperature show possible increases from the first to last future period, with higher magnitude during summer when could reach about 5.4°C for RCP4.5 and 11.0°C for RCP8.5 at the end of century (2081-2100). Considering that the climatological value of summer maximum temperature is 30°C (1985-2006) an increase of 11°C to the end of century for RCP8.5 means values around 41°C.
2.2.2 Extreme temperature: 5th percentile of minimum temperature and 95th percentile of maximum temperature
Extreme temperature reveals important future changes at Cesena. An increase in annual 5th percentile of minimum temperature of 0.7°C is projected during the first future period and up to 1.8°C to the end of the century, in the framework of moderate emission scenario. The signal is more intense for high-emissions scenario and especially during 2061-2080 and 2081-2100 periods, when the annual increases could reach 2.6°C and 3.5°C, respectively. At seasonal level, a higher amplitude of changes is expected to occur during autumn of 5.9°C and during winter and spring of 3.0°C, for high-emissions climate scenario.
The projections of future changes of 95th percentile of maximum temperature in Cesena shows an increase in annual value of changes between 1.1°C and 2.4°C for moderate scenario and between 1.3°C and 5.0°C for high emission scenario, from 2021-2040 to 2081-2100. A deep analysis on projected changes reveals that higher values are expected to occur during summer season, for both emission scenarios.
2.2.3 Heat waves duration
The heat wave duration index is defined as the maximum number of consecutive days with the maximum temperature greater than 90th daily percentile. The future climate projection in figure 3 shows an increase in the warm part of the year, especially in spring. In the framework of moderate climate scenario, the increase is for 44 consecutive days, and in the case of the high-emission scenario, it could reach 84 consecutive days.
Figure 3: Seasonal heat wave duration: observed values over the reference period (in red), changes projected by statistical downscaling applied to 4GCMs and the Ensemble Mean of changes over the four periods (P1, P2, P3, P4) projected in the framework of RCP 4.5 (left) and RCP 8.5 (right.) A significant change is marked by a star.
2.2.4 Tropical nights
The analysis of the number of summer nights in which the temperature remains above 20°C in Cesena shows a significant prolongation of those periods. The climate value of this index for Cesena is around 16 nights in summer, during 1986-2005 period. The number of added tropical nights varies between 20 and 51 for moderate climate scenario and between 22 to 72 days for a high-emissions scenario, over the four periods.
2.2.5 Frost days
The future projections of frost days, namely the number of days with a minimum temperature lower than 0°C, show a decrease during winter, spring and autumn. The climate value of this index for Cesena is around 32 days in winter, during 1986-2005 period. The future projections during winter show a decrease respect to present climate up to -16 days towards the end of the century in the moderate scenario and -22 days with high-emissions scenario.
3 Precipitation related data
3.1 Results from dynamical downscaling:
3.1.1 Averaged precipitation
Averaged precipitation obtained by dynamical downscaling is expressed in mm/day and its change in the future is shown as relative to the same reference period as for temperature. Precipitation is a much more variable parameter than temperature, therefore there is not a unique sign of change neither through the year nor from model to model (Figure 4). The change in ensemble mean for Cesena gives increase of precipitation in all seasons except in spring.
Increase on annual scale (2.9%) at the end of 21st century for moderate scenario.
For the pessimistic climate scenario, precipitation will decrease in summer (-18.8%) and increase in all other seasons. On annual scale precipitation will decrease (-3.4%).
Figure 4: Averaged seasonal and annual precipitation obtained by dynamical downscaling for Cesena: Ref. mean is 20 years simulated period (1986-2005) for the ensemble mean in mmday-1; P1-P0, P2-P0, P3-P0, P4-P0 are the changes (in %) in the future for following periods P1: 2021-2040, P2: 2041-2060, P3: 2061-2080, P4: 2081-2100. Differences are shown for individual models. A significant change is marked by a star. Change is also shown as ensemble mean (ENSMEAN), not tested for significance. The left column is for the moderate scenario and the right one for the high-emissions scenario.
3.1.2 Intense precipitation
The amounts of intense precipitation (defined by 95th percentile of precipitation) in Cesena increase will be between 3.1% in spring and 12.3% in winter, 5.2% on annual scale for moderate scenario.
For high-emissions scenario increase will be between 3.7% in spring and 12.4% in autumn, 0.8% on annual scale.
3.1.3 Extreme precipitation
Extreme precipitation, defined by 99th percentile of precipitation, in Cesena shows the increase in spring and autumn and on an annual scale. The increase will change from 8.7% in autumn to 11.7% in spring, 2.6% for annual scale for the moderate scenario.
For the high-emissions scenario mean change is positive for all seasons except in summer, between 2.1% in winter and 13.4% in autumn, 7.2% for annual scale at the end of 21st century.
3.2 Results from statistical downscaling
3.2.1 Amount of precipitation
The future change of annual precipitation obtained by statistical downscaling shows an overall decrease of precipitation, more pronounce at the end of the century when could decrease up to -40% for the moderate scenario and to -60% for the high emission scenario. At seasonal level, the decrease is more pronounced during summer.
3.2.2 Intense precipitation
Intense precipitation, defined by 90th percentile of daily precipitation, shows for Cesena a decrease at annual level, up to -15% for moderate climate scenario and up to -20% for high-emissions climate scenario.
3.2.3 Extra rare humidex projections
Extra rare humidex change (defined by 99.9th percentile of humidex Figure 5) in the future in Cesena will increase towards the end of 21st century. Ensemble mean will increase between 1.3 in autumn and 1.9 in spring, were slight negative change is noticed -0.7 for summer and -0.3 on annual scale for moderate emission scenario. High-emission climate scenario gives higher positive amplitudes, from 4.6 in spring to 6.0 in autumn, 3.6 on annual scale.
Figure 5: Seasonal and annual 99.9th percentile of humidex obtained by dynamical downscaling for Cesena (in ): Ref. mean is 20 year simulated period (1986-2005); P1-P0, P2-P0, P3-P0, P4-P0 are changes in the future for following periods P1: 2021-2040, P2: 2041-2060, P3: 2061-2080, P4: 2081-2100. Differences are shown for individual models. Significant change is marked by star. Change is also shown as ensemble mean (ENSMEAN), not tested for significance. Left column is for RCP4.5 scenario and right for RCP8.5 scenario.
3.2.4 Consecutive dry days
The consecutive dry days, defined as the maximum number of consecutive days without precipitation show an increase especially in spring and summer and, a decrease in winter and autumn. High magnitude of increases is projected in spring, between up to 12 days for moderate emission scenario and up to 30 for high-emission climate scenario.
The above framework of climate projections underlines for Cesena changes of simple and combined climate indices, with higher magnitude especially on 2061-2080 and 2081-2100. Significant changes have been projected for: tropical nights, frost days, heat wave duration, lower and upper percentile of temperature, intense precipitation, droughts periods and extra rare humidex index ( especially in winter and spring).