A Simple Framework for Likely Climate Projections Applied to Tropical Width

Confronted with the difficult task of choosing between a wide range of climate models and emission scenarios, scientists are often left questioning which models and scenarios are most representative of our future climate. Currently, most climate projections use the highest emission scenario and an evenly weighted ensemble of all available climate models despite substantial evidence that the continuously rising emissions in the high emission scenario are unrealistic, and that some models are more reliable than others. As a result, unlikely climate projections have been presented as our likely future. Here, we present a simple and easy to use framework for creating projections of our likely future climate using available model data. The framework involves three measures: selecting the most likely emission scenario, choosing the most reliable models, and debiasing against reanalysis data. To demonstrate our framework and its components, we estimate future changes in tropical width, a hydrologically important climate feature. Our projections show that the likely tropical expansion is roughly half of previous estimates. This framework can be easily applied to other climate features, allowing for better estimates of likely future conditions.