Many Earth-system models well reproduce the real-world climate under various aspects, but still disagree on the amount of global warming that may be reached in the future under sustained emissions of greenhouse gases. The research studies how much of this uncertainty can be reproduced with a single climate model by changing some of the parameters controlling the physics of clouds and convection. The result suggests that parameters play a minor role and that the main cause of the disagreement between different models lies more deeply inside the models' structure.