## 3 Methods and Data  
### Study Area  
The Porto Metropolitan Area (PMA) has 17 municipalities and 1,737,395 inhabitants (a reduction of 1.26% between 2011 and 2021) (INE, 2021) spread over almost 2.040 km\({}^{2}\). In 2021, 16.8% of the Portuguese population resided in NUTS III PMA [42]. The main tourist destination in the urban and city breaks segment is Porto, which indicates the recognition of its quality among the main tourist destinations in Portugal and Europe (e.g., European Best Destination, 2012, 2014 and 2017). In 2021, Porto was ranked among the 100 cities with the highest tourism performance index (68 th place according to Euromonitor International) [43].  
Considering the geographical location, tourism will certainly be affected by significant changes in weather patterns [44], notably by:  
1. Increase in the number of hot days (between 23 to 62 days) and very hot days (between 5 to 15 days);
2. Higher frequency of heat waves and increased temporal duration;
3. Increase in the number of tropical nights, which can reach 21 nights;* Increase of 5 days per year of drought for each increase of 100 ppm of CO2.  
Figure 1 summarizes the main climate risks identified in each municipality (PMA), reflecting the type of effects of climatic-meteorological and hydrometeorological conditions in the area under study.  
In this context, extreme climatic events are likely to occur in a framework of climate variability in the medium and long term, with a tendency to become more intense. However, proximity and distance from the coastline or urban morphology (especially densification) may contract or intensify the risk level.  
Figure 1: Study area—main climate risks identified. Source: [PERSON] (2022) [45].  
In view of this climate vulnerability scenario, several positive or negative effects (and in some circumstances both) on tourism can be identified (Table 1).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Climatic Variable** & **Tendency** & **Projected Changes** &
\begin{tabular}{c} **Influence on the** \\ **Tourism Sector** \\ **(Level and Direction)** \\ \end{tabular} \\ \hline
**Temperature** & \begin{tabular}{c} **Annual and seasonal average** \\ Annual average temperature rise, between 1 \({}^{\circ}\)C \\ and 4 \({}^{\circ}\)C at the end of the century. \\ Significant increase in \({}_{\text{Tmax}}\) in autumn \\ (between 1.3 \({}^{\circ}\)C and 3.6 \({}^{\circ}\)C) and summer \\ Annual average \\ temperature rise, \\ in particular \\ maximum temperatures \\ \end{tabular} & \
\begin{tabular}{c} **Annual and seasonal average** \\ Annual average temperature rise, between 1 \({}^{\circ}\)C \\ (between 1.3 \({}^{\circ}\)C and 3.6 \({}^{\circ}\)C) and summer \\ (between 1.3 \({}^{\circ}\)C and 4.1 \({}^{\circ}\)C). \\ \end{tabular} &
\begin{tabular}{c} _Level_ \\ **(Level and Direction)**  
These effects may influence the destination differently, relying on the level (depending on whether it is high or low) or the direction (whether it is positive or negative). The effects of the increase in temperature, for instance, are notoriously relevant. Nevertheless, even though the aforementioned increase may cause problems in the summer, it can be beneficial in the winter.  
Regarding the climate change risk reaction in the tourism sector, it is worth mentioning all the identifiable positive (softening) and negative (aggravating) aspects in PMA when it comes to the climate change scenario, with the collaborative contribution of regional and local stakeholders. Based on this articulation, the measures to be established will be more oriented to issues affecting these communities, tourism segments, and stakeholders' network participation.