Objective: Systems thinking can be counterintuitive to everyday ways of knowing. This can surface doubt around predicted patterns of emergence in complex systems data, especially as it relates to the current climate crisis and related justice-oriented solutions. Method: Our study describes a four-year design-based research project in which we engaged high school biology students in complex systems modelling to understand linkages between increasing ocean temperatures and the rate and severity of disease outbreaks in sea stars. Results: Our findings showed that students approached climate data with uncertainty and viewed their lives as separate from the impacts of climate change. Through iterative design work, youth used authentic data and computational tools to construct geospatial and causal-loop models of climate-related disease outbreaks that situated case studies within broader socioecological and sociotechnical contexts of historic and powered human actions. Through a speculative design lens, models were transformed from data visualization tools to mediums for storying and re-storying present and future worlds for multispecies survival in the face of the climate crisis. Conclusion: Students shifted their understandings of disease outbreaks from a technical perspective to a more social and situated lens of care and responsibility for mitigating the impacts of the climate crisis on human and more-than-human communities.