Climate-denying rumor propagation in a coupled socio-climate model: Impact on average global temperature

2.2 Earth system model A relation between emissions and temperature is required to understand the increase in tem- perature due to emissions. Earth system models (ESMs) describe climate-relevant Earth pro- cesses and how they influence climate dynamics. A simple existing Earth system model is used for this purpose [55]. An austere climate–carbon-cycle model for understanding the coupled climate-carbon–cycle system defines the global mean surface temperature anomaly (controlled by the upper ocean) as follows: dT dt ¼ qF T d ð1:2Þ F ¼ F2x lnð2Þ ln Catm C0 � � ð1:3Þ where F ¼ F2x lnð2Þ ln Catm C0 � � is the CO2 radiative forcing and C0 is the pre-industrial atmospheric CO2 level and Catm is the atmospheric CO2 level at the time point [55]. F2x is the forcing due to CO2 doubling, q is the thermal adjustment of the upper ocean, and d is the thermal equilib- rium for the upper ocean. The global mean surface temperature anomaly helps in understand- ing the change in temperature that has occurred over the years and projecting future changes concerning the emission levels (S1 Table). This ESM has been used to calculate the tempera- ture anomaly under different emissions scenarios [56]. 2.3 Coupled rumor—Climate change model The rumor propagation model in section 1.1 is modified by incorporating climate dynamics. The coupling is accomplished by making the individual believing probability η and group believing probability ω a function of the change in temperature, T, defined as: ZðTÞ ¼ Z0e vT ð1:4Þ oðTÞ ¼ o0e vT ð1:5Þ

The parameters in the system Eq 1.1 are described in S1 Table. According to Eqs 1.4 and 1.5, the believing probability increases or decreases in response to the change in the temperature (T). As T increases, η and ω decrease: fewer individuals are convinced by the rumors since they experience the temperature change. This will decrease the believing probability and increase the rejecting probability. The deviation of the global atmospheric CO2 levels from the pre-industrial levels, C, is defined as: dC dt ¼ EðtÞ t � 2021 E2021 ∗ expð CP kiRk Þ dC t > 2021 8 < : ð1:6Þ where E(t) is the anthropogenic emission data for each year until 2021, C is a constant value at which the rejectors limit their emissions, which is any mitigation strategies considered by the rejector to reduce their emissions, like switching to renewable energy like solar energy for power consumption, using electric or hybrid vehicles, insulating walls during construction, etc. E2021 is the baseline carbon dioxide emissions level in the absence of rejectors (amount in 2021). According to Eq 1.6, CO2 emissions fall when the rejector population increases PLOS ONE Climate-denying rumor propagation in a coupled socio-climate model: Impact on average global temperature PLOS ONE | https://doi.org/10.1371/journal.pone.0317338 January 16, 2025 5 / 18