Added Values of CMIP5 Models in Reducing the Uncertainty Range of Future Projections over China Using Unequal-Weighted Average.

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Title: Added Values of CMIP5 Models in Reducing the Uncertainty Range of Future Projections over China Using Unequal-Weighted Average.
Authors: Fan, Wenlu1,2 (AUTHOR), Tian, Zhiping1 (AUTHOR), Jiang, Dabang1,2 (AUTHOR) jiangdb@mail.iap.ac.cn
Source: Journal of Climate. Apr2026, Vol. 39 Issue 7, p1657-1667. 11p.
Subjects: Climate change models, Ensemble learning, Climate change forecasts, Weather & climate change, Climate change
Geographic Terms: China
Abstract: To enhance the skill of climate projections, researchers have developed various weighting schemes based on the performance of models in simulating historical climate. However, the capacity of models with these weighting methods to accurately reproduce future climate change remains uncertain. In this study, models from the Coupled Model Intercomparison Project phase 5 (CMIP5) with reliability ensemble averaging (REA) scheme and performance and independence (PI)-weighted scheme are employed to project near-term temperature changes over China. By comparing observations with the weighted ensemble averages of models, we evaluate the projection skill of CMIP5 ensembles using these two weighting methods for the near-term projections. Our results indicate that, compared to the equal-weighted ensemble mean, PI-weighted projections based on the performance in reproducing historical temperature trends at the gridcell level display overall improvements in spring, summer, and autumn. Meanwhile, REA-weighted projections perform slightly worse on both annual and seasonal scales than the equal-weighted ensembles. Of importance is that the projection uncertainties, measured by the range of 5th–95th percentiles, estimated by the two unequal-weighted schemes are generally lower than those of the equal-weighted approach. However, the small projection uncertainty with large biases in REA-weighted ensembles increases the undesirable risk of observations falling outside the uncertainty range. As reducing the projection uncertainty also extends to the next two decades by weighting, the PI-weighted ensemble serves as a reliable alternative for future temperature projections over China. [ABSTRACT FROM AUTHOR]
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Abstract:To enhance the skill of climate projections, researchers have developed various weighting schemes based on the performance of models in simulating historical climate. However, the capacity of models with these weighting methods to accurately reproduce future climate change remains uncertain. In this study, models from the Coupled Model Intercomparison Project phase 5 (CMIP5) with reliability ensemble averaging (REA) scheme and performance and independence (PI)-weighted scheme are employed to project near-term temperature changes over China. By comparing observations with the weighted ensemble averages of models, we evaluate the projection skill of CMIP5 ensembles using these two weighting methods for the near-term projections. Our results indicate that, compared to the equal-weighted ensemble mean, PI-weighted projections based on the performance in reproducing historical temperature trends at the gridcell level display overall improvements in spring, summer, and autumn. Meanwhile, REA-weighted projections perform slightly worse on both annual and seasonal scales than the equal-weighted ensembles. Of importance is that the projection uncertainties, measured by the range of 5th–95th percentiles, estimated by the two unequal-weighted schemes are generally lower than those of the equal-weighted approach. However, the small projection uncertainty with large biases in REA-weighted ensembles increases the undesirable risk of observations falling outside the uncertainty range. As reducing the projection uncertainty also extends to the next two decades by weighting, the PI-weighted ensemble serves as a reliable alternative for future temperature projections over China. [ABSTRACT FROM AUTHOR]
ISSN:08948755
DOI:10.1175/JCLI-D-25-0443.1