3.2.1. Tourism Development

Compared with a single indicator, this paper adopts tourism development indicators [57], including the tourism economy and tourism scale, to measure the level of tourism development more comprehensively. Based on the domestic tourism income and number of people, inbound tourism income and the number of people under the city scale, the entropy weight TOPSIS method is used to obtain the tourism development level (TC) of 280 cities nationwide, which is used as the core explanatory variable of this spatial econometric model.

#### 3.2.2. Carbon Emission Intensity

Urban carbon emissions include carbon emissions from direct energy consumption as well as carbon emissions from electric energy and thermal energy consumption. Drawing on the related research [58], carbon emissions from liquefied petroleum gas, transportation, electric energy and thermal energy consumption are summed to obtain the total urban carbon emissions. The ratio of the total carbon emissions of a city to its GDP is used to measure the intensity of carbon emissions of the city.
