פרסומים

Climate change is one of the most pressing challenges of our time, requiring accurate predictions to guide effective mitigation and adaptation strategies. Central to this effort is the need to estimate and better understand the physical mechanisms behind effective radiative forcing (ERF) from anthropogenic activities. ERF encompasses both the instantaneous radiative forcing from external forcing agents, such as greenhouse gases and aerosols, and the subsequent radiative adjustments, particularly those involving cloud changes. A major and persistent source of uncertainty in ERF estimates is anthropogenic aerosols, especially absorbing aerosols.

In this paper, we present a hierarchy of convective-permitting simulations to investigate ERF and cloud adjustments to absorbing aerosols. This first-of-its-kind model hierarchy spans small-domain simulations (capturing local responses), large-domain simulations (representing convective aggregation and large-scale tropical circulation), and mock Walker simulations (accounting for geographically oriented, sea surface temperature gradient-driven circulation). Our results demonstrate that ERF is primarily driven by cloud adjustments and that the baseline cloud regime distribution plays a crucial role in determining ERF. Specifically, as the simulation scale shifts from small-domain to large-domain and to mock Walker setup, the baseline cloud regime transitions from ice-dominated to shallow-cloud-dominated. Since shallow clouds are more susceptible to absorbing aerosol perturbations, cloud adjustments—and consequently ERF—increase across this hierarchy, from small to large to mock Walker simulations.

While the role of social media in the spread of conspiracy theories has received much attention, a key deficit in previous research is the lack of distinction between different types of platforms. This study places the role of social media affordances in facilitating the spread of conspiracy beliefs at the center of its enquiry. We examine the relationship between platform use and conspiracy theory beliefs related to the COVID-19 pandemic. Relying on the concept of technological affordances, we theorize that variation across key features make some platforms more fertile places for conspiracy beliefs than others. Using data from a crossnational dataset based on a two-wave online survey conducted in 17 countries before and after the onset of the COVID-19 pandemic, we show that Twitter has a negative effect on conspiracy beliefs—as opposed to all other platforms under examination which are found to have a positive effect.