## 2 Methods and Data Sources  
### Methods for Measuring Carbon Emissions in the Tourism Industry  
Currently, there are two main methods for estimating carbon emissions in the tourism industry: the \"top-down\" approach and the \"bottom-up\" approach. The \"top-down\" approach involves using a comprehensive monitoring system to calculate the proportion of energy consumption and carbon emissions in the tourism industry. The \"bottom-up\" measurement method primarily involves calculating carbon emissions starting from the consumer end. It sequentially accounts for the carbon emissions generated during various aspects of the tourist's journey, including transportation modes used, tourist activities undertaken, and accommodations utilized. Since China does not yet have a complete statistical monitoring system for greenhouse gas emissions, this study adopts the \"bottom-up\" approach to estimate carbon emissions in the tourism industry from 2019 to 2020. The estimation primarily focuses on three aspects: tourism transportation, tourism accommodation, and tourism activities. The formula for calculating carbon emissions in the tourism industry is as follows:  
\[C_{n}^{e}=C_{t}^{e}+C_{a}^{e}+C_{p}^{e} \tag{1}\]  
\(C_{n}^{e}\) is the total carbon emissions from tourism, \(C_{t}^{e}\) is the carbon emissions generated by tourists during transportation, \(C_{a}^{e}\) refers to the carbon emissions generated by tourist activities during accommodation, and \(C_{p}^{e}\) refers to the carbon emissions generated by tourists engaging in different tourism activities. The formula for calculating carbon emissions from tourism transportation is as follows:  
\[C_{t}^{e}=\sum_{i=1}^{31}\sum_{j=1}^{4}Q_{ij}^{t}\times P_{j}\times\alpha \tag{2}\]  
In this equation, \(Q_{ij}^{t}\) represents the passenger turnover of tourism transportation mode \(j\) (railway, road, waterway, civil aviation) in province \(i\) in year \(t\). \(P_{j}\) represents the proportion of tourists using transportation mode \(j\) (Table 1), and \(\alpha\) represents the carbon emission factor for transportation mode \(j\) (Table 2). The formula for calculating carbon emissions from tourist accommodation is as follows:  
\[C_{a}^{e}=\sum_{i=1}^{31}L_{i}^{E}\times O_{i}^{E}\times n\times\gamma \tag{3}\]  
In this equation, \(L_{i}^{E}\) represents the total number of beds in star-rated hotels in province \(i\) in year \(E\), \(O_{i}^{E}\) represents the room occupancy rate in province \(i\) in year \(E\), \(n\) represents \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**PUOT** & **Sightsee** & **Lei Vac** & **BT** & **VRF** & **Others** \\ \hline POT (\%) & 26.35 & 18.55 & 14.80 & 33.50 & 6.80 \\ \hline \hline \end{tabular} Note: The proportion of tourists for different tourism purposes is obtained from the “China Domestic Tourism Development Annual Report 2021” published by the China Tourism Academy.  
\end{table} 
Table 1: Proportion of tourist arrivals for different tourism purposes. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **RLY** & **HWY** & **WTWY** & **CV Avn** \\ \hline CAEF & 27 & 133 & 106 & 137 \\ (gco\({}_{2}\)/pkm) & POT (\%) & 31.6 & 13.8 & 10.6 & 64.7 \\ \hline \hline \end{tabular} Note: The carbon emission factors and tourist proportions for different tourism transportation modes are sourced from [8]. The passenger turnover of various transportation modes in each province in China from 2019 to 2020 is obtained from the Statistical Yearbook of each province for 2020-2021 and the Ministry of Transport of the People’s Republic of China. CAEF (Purpose of the tour); POT (Proportion of tourists); RLY (Railway); HWY (Highway); WTWY (waterway); CV Avn (Civil aviation).  
\end{table} 
Table 2: Calculation parameters of carbon emissions of tourism transportation modes. 365 days, and \(\gamma\) represents the carbon emission factor for tourist accommodation. According to existing literature studies [11; 12; 13; 14; 15; 16], the carbon emission factor for tourist accommodation is determined as 2.458 g/bed/night.