## 2 Methodology
### Weather Files
#### 2.4.3 Changes in the Climate of Lisbon  
The changes suffered by the environment over these past years have been greatly caused by the emission of greenhouse gases due to anthropogenic activities [54]. For example, in Lisbon, which is a coastal city and the largest city in Portugal with over 2.8 M people [55], it is expected that the annual precipitation will decrease. On the other hand, it is also expected that the number of extreme phenomena with extreme rains will increase, droughts will become more frequent and more severe, and both the air temperature and the average sea level will rise [26]. In order to study the changes in the outdoor climate over the years in Lisbon, three sets of temperature and precipitation were analysed: (1) 1951-1980, (2) 1970-2000, and (3) 2005-2015. The first set was supplied by the old Meteorological Institute (now IPMA) and used by [PERSON] [56] to analyse the variability of the outdoor climate in eight climate representative cities of Portugal--Braganca, Porto, Portalegre, Lisboa, Beja, Faro, Ponta Delgada (Acores archipelago), and Funchal (Madeira archipelago). The second set was obtained from the IPMA website [57], and the third set was supplied by IPMA for other projects [58]. Although the third set does not cover the required 25-30 years to assess the climate variability [59], only including 11 years' worth of data, the obtained results are still used here because they are representative of the more recent climate of Lisbon. Overall, the mean temperature in Lisbon considerably increased from 1951-1980 to 1970-2000, with the difference amounting to +4.0 \({}^{\circ}\)C (Figure 5). The only month in which the average temperature corresponding to 1970-2000 is not higher than the average temperature of 1951-1980 was May (\(-\)0.3 \({}^{\circ}\)C). The highest increases occurred in March (+0.8 \({}^{\circ}\)C) and in December (+0.7 \({}^{\circ}\)C). The same observation can be made whilst comparing the values that correspond to 1951-1980 and 2005-2015, i.e., the mean temperature considerably increased throughout the whole year (Figure 5). The difference amounts to +7.7 \({}^{\circ}\)C, and the highest increases occurred in April (+1.1 \({}^{\circ}\)C) and in December (+1.0 \({}^{\circ}\)C). Figure 5: Normals of the average outdoor temperature for three periods: 1951–1980 (used in Ref. [56]), 1970–2000 [57], and 2005–2015 (used in Ref. [58]). The precipitation accumulated difference between 1951-1980 and 1970-2000 is approximately \(-\)52 L/(m\({}^{2}\)h), which means that the precipitation in Lisbon has decreased significantly from 1951-1980 to 1970-2000 (around 7%). The highest difference occurred in March, with a decrease of ca. \(-\)50 L/(m\({}^{2}\)h) (Figure 6). However, the difference in January (\(-\)25 L/(m\({}^{2}\)h)), February (\(-\)18 L/(m\({}^{2}\)h)), and December (\(-\)15 L/(m\({}^{2}\)h)) is also considerable. On the other hand, the precipitation increased substantially in May (+12 L/(m\({}^{2}\)h)) and April (+11 L/(m\({}^{2}\)h)), but it was not enough to compensate for the decrease that occurred in the other months. When comparing 1951-1980 and 2005-2015, the difference in terms of precipitation is even higher (Figure 6), i.e., the precipitation decreased ca. \(-\)127 mm, around 16% when compared to the 1951-1980 value. The most significant decreases occurred in March (\(-\)43 mm), December (\(-\)42 L/(m\({}^{2}\)h)), and January (\(-\)40 L/(m\({}^{2}\)h)). On the other hand, the precipitation increased substantially in October (+23 L/(m\({}^{2}\)h)) and November (+20 L/(m\({}^{2}\)h)) and slightly in September (+5 L/(m\({}^{2}\)h)), but, once again, these increases are not enough to compensate for the decreases in precipitation that occur in the other months of the year. In addition, the average monthly maximum and minimum were compared for the periods of 1951-1980 and 1970-2000. It is visible that the difference in the maximum temperatures is not as substantial as one would expect (Figure 7a).