Historical diurnal temperature range trends constrain future climate projections

In the late twentieth century, nighttime land surface temperatures are observed to rise faster than daytime temperatures, resulting in high diurnal temperature ranges and considerable diurnal asymmetric warming. Nevertheless, the projected changes in diurnal temperature ranges under global warming remain with large uncertainties across statistical multi-model simulations. Here, we identify an emergent relationship between historical diurnal temperature ranges variability and future projections on both global and regional scales. By leveraging this spatially heterogeneous relationship, we present a framework to refine regional projections, reducing model uncertainties by 15–68% across the 27 IPCC AR6 reference regions. Our findings suggest a sustained influence of external forcing on diurnal temperature ranges from past to future, driven primarily by related widespread reductions in cloud cover, rather than internal variability. This study provides valuable insights into constraining regional extreme responses to a warming climate, laying the groundwork for informed regional climate policy decisions. The diurnal temperature range (DTR), which measures the difference between daily maximum and minimum temperatures, is a vital indicator of climate extremes. However, predicting future changes in DTR under global warming remains challenging due to significant uncertainties in model projections. This study uncovers a significant link between historical DTR trends and future projections on both global and regional scales. Leveraging this relationship, we introduce a constraining framework to enhance the accuracy of regional climate projections. The mechanism is that the changes in DTR are primarily driven by external forces such as greenhouse gas emissions, rather than internal climate variability. Increasing greenhouse gases reduces cloud cover, which migrates DTR decline by enhancing daytime shortwave radiation and reducing nighttime longwave radiation. While this relationship is generally robust across seasons, it weakens at high latitudes in winter due to minimal solar radiation. Our findings contribute to reducing uncertainties in model projections, offering valuable insights into future changes in DTR and their implications for regional climate responses. The identification of a strong link between historical diurnal temperature range trends and future projections can be used to constrain regional climate projections with greater accuracy, according to a study based on reanalysis data and CMIP6 simulations.