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

exponentially at a constant value C. Apart from this, emission gets naturally dissipated due to various natural processes (sinks like ocean, land, and plants), and this natural dissipation rate is δ. Usually, the time scale of rumor propagation and climate change is not comparable. Rumor propagation might last for weeks or months, whereas climate change takes place over decades. To overcome this issue, the long-term susceptibility and transmission of individuals is mod- eled to a collection of multiple related rumors. This means that an individual who is a believer (rejector), believes (rejects) various rumors that come up over time, and not just a single rumor. 2.4 Analysis Time series, univariate, and bivariate (parameter plane) sensitivity analysis is used to under- stand the model’s behavior dynamics and parameter sensitivity. The baseline parameter values for the model were generated using Approximate Bayesian Computation (ABC) [57, 58], and the baseline climate parameters are obtained from the ESM [55], and the Global Carbon Bud- get [56]. The parameter range considered for sensitivity analysis depends on the upper and lower bound of the model parameters. These bounds are chosen in accordance with the nature of the parameter. For example, the parameters representing the probability values are consid- ered between 0 and 1, and hypothetical model parameters are given broad upper and lower bounds, specified in S1 Table. The analysis has been carried out over 180 years which began when the rumor propagation emerged in 2021. 3 Results

The model illustrates how social behavior, through rumor propagation, influences temperature levels. Initially, the whole population is susceptible to the rumors (s0 ¼ 1; h0 ¼ 0; ib0 ¼ 0; ir0 ¼ 0). A time series examination of the model indicates that a grow- ing proportion of rejectors in the population causes lower emission levels depending on their emission-limiting strategies, as expected (Fig 1(a) and 1(b)). The transmission of multiple rumors and that a believer (rejector) believes (rejects) all the rumors that come up over time is considered. The result shows an optimistic case where 80% of rejectors are present in the pop- ulation, with strong emission-limiting strategies to keep the temperature anomaly below 1.5˚C (Fig 1(b)), which is considered to be an important climate change threshold [4]. Human actions predominantly affect climate through increased emissions, leading to the accumulation of greenhouse gases in the atmosphere, leading to severe and potentially irre- versible changes. In this model, rumor propagation begins in 2021. The emissions and corre- sponding temperature anomalies before 2021 are computed using the anthropogenic emission data [56]. When individuals encounter rumors about climate change–such as climate change is not a serious problem or climate change is not real–they think about it and initially hesitate to decide whether to believe or reject it. The hesitating state can simply be considered as the state in which individuals are contemplating or checking facts before making their decision.

Later, they decide whether to believe or not believe the rumors. The rejectors do not further spread the rumor, act like mitigators, and try to limit their emissions to reduce the impact of climate change, whereas the believers forward the rumor to more individuals, and the rumor spreads through the population. Individuals stop believing the series of rumors when they experience a temperature change. As the proportion of rejectors increases in the population, the emission level slowly decreases, and so does the temperature. The temperature change is due to the cumulative amount of greenhouse gases in the atmosphere, especially CO2. The atmospheric CO2 does not reduce 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 6 / 18