The climate projections we use come from the CORDEX downscaling project. Which takes global climate models and simulates these at a higher resolution over each region of the world. These downscaled projections have an approximately 50km resolution. For some regions we will have much higher resolution data because there have been projects that have produced finer scale modelling (e.g. over southeast Australia there is data at 10 km resolution).
Please see the latest XDI Climate & Hazard Modelling Methodology Document for more details.