AI天气模型在气候变化下仍能准确预报,展现跨气候态泛化能力。
Robustness of AI-based weather forecasts in a changing climate
- 用当前天气模型跨预工业、现况和2.9℃变暖气候进行预测
- 模型在各气候态下表现良好,但部分出现全球均温冷/暖偏差
- 适合关注气候模拟与AI融合的研究者及政策制定者
近1-2年,基于数据的机器学习天气预报模型取得突破性进展,其性能已超越最佳物理模型。鉴于天气与气候建模的紧密关联,这引发疑问:机器学习能否同样革新气候科学,例如支持减缓与适应策略或生成更大集合以提升不确定性估计。本文表明,当前最先进的机器学习天气预报模型在现今日气条件下训练后,可在预工业、现况及未来2.9K变暖气候状态下仍产生有技能的预报。这表明短期天气动力机制在气候变化中可能未发生根本改变。同时,展示了模型具备关键的分布外泛化能力,为气候应用奠定基础。然而,两个模型在变暖气候下出现全球平均冷偏差(即向训练所用的现况气候漂移),类似地,在预工业情景中,三分之二的模型表现出变暖倾向。我们讨论了这些偏差的可能修正方法,并分析其空间分布,揭示复杂升温与降温模式,部分与训练数据中缺失的海洋-海冰及陆表信息有关。尽管存在当前局限,结果表明数据驱动的机器学习模型将成为气候科学的强大工具,有望通过补充传统物理模型而变革既有方法。
原文摘要 · Abstract (English)
Data-driven machine learning models for weather forecasting have made transformational progress in the last 1-2 years, with state-of-the-art ones now outperforming the best physics-based models for a wide range of skill scores. Given the strong links between weather and climate modelling, this raises the question whether machine learning models could also revolutionize climate science, for example by informing mitigation and adaptation to climate change or to generate larger ensembles for more robust uncertainty estimates. Here, we show that current state-of-the-art machine learning models trained for weather forecasting in present-day climate produce skillful forecasts across different climate states corresponding to pre-industrial, present-day, and future 2.9K warmer climates. This indicates that the dynamics shaping the weather on short timescales may not differ fundamentally in a changing climate. It also demonstrates out-of-distribution generalization capabilities of the machine learning models that are a critical prerequisite for climate applications. Nonetheless, two of the models show a global-mean cold bias in the forecasts for the future warmer climate state, i.e. they drift towards the colder present-day climate they have been trained for. A similar result is obtained for the pre-industrial case where two out of three models show a warming. We discuss possible remedies for these biases and analyze their spatial distribution, revealing complex warming and cooling patterns that are partly related to missing ocean-sea ice and land surface information in the training data. Despite these current limitations, our results suggest that data-driven machine learning models will provide powerful tools for climate science and transform established approaches by complementing conventional physics-based models.
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