Short answers, pulled from the story.
The Intergovernmental Panel on Climate Change released its Sixth Assessment Report in 2021. This document introduced Shared Socioeconomic Pathways as a new set of climate change scenarios.
SSP1 describes a world shifting toward a more sustainable path by the end of the century. This scenario emphasizes inclusive development that respects predicted environmental boundaries and reduces inequality across countries and within them.
Regional Rivalry defines national priorities through resurgent nationalism where concerns about competitiveness and security push countries to focus on domestic issues. Policies shift over time to become increasingly oriented toward national and regional security issues at the expense of broader-based development.
Scientists quantify these Shared Socioeconomic Pathways using various Integrated Assessment Models. A study published in Geoscientific Model Development in 2020 detailed projected atmospheric CO₂ concentrations across the 21st century based on simulated values generated from five integrated assessment models.
Highly unequal investments in human capital characterize the fourth scenario called Inequality. Increasing disparities in economic opportunity and political power lead to growing stratification across and within countries with social cohesion degrading as conflict becomes common.