H-CEL, Ghent University, Ghent, Belgium.
LMD/IPSL, Sorbonne Université, Paris, France.
Nature. 2024 Sep;633(8030):594-600. doi: 10.1038/s41586-024-07887-y. Epub 2024 Sep 18.
Climate models indicate that dry extremes will be exacerbated in many regions of the world. However, confidence in the magnitude and timing of these projected changes remains low, leaving societies largely unprepared. Here we show that constraining model projections with observations using a newly proposed emergent constraint (EC) reduces the uncertainty in predictions of a core drought indicator, the longest annual dry spell (LAD), by 10-26% globally. Our EC-corrected projections reveal that the increase in LAD will be 42-44% greater, on average, than 'mid-range' or 'high-end' future forcing scenarios currently indicate. These results imply that by the end of this century, the global mean land-only LAD could be 10 days longer than currently expected. Using two generations of climate models, we further uncover global regions for which historical LAD biases affect the magnitude of projected LAD increases, and we explore the role of land-atmosphere feedbacks therein. Our findings reveal regions with potentially higher- and earlier-than-expected drought risks for societies and ecosystems, and they point to possible mechanisms underlying the biases in the current generation of climate models.
气候模型表明，世界上许多地区的干旱极端情况将加剧。然而，对于这些预计变化的幅度和时间，人们的信心仍然很低，这使得社会在很大程度上毫无准备。在这里，我们展示了使用新提出的突现约束（EC）通过观测来约束模型预测，可以将核心干旱指标——最长年干旱期（LAD）的预测不确定性降低 10-26%。我们的 EC 校正预测显示，LAD 的增加平均将比目前“中等范围”或“高端”未来强迫情景所表明的增加高出 42-44%。这些结果意味着，到本世纪末，全球陆地平均 LAD 可能比目前预期的长 10 天。使用两代气候模型，我们进一步揭示了历史 LAD 偏差影响预测 LAD 增加幅度的全球区域，并探讨了其中陆地-大气反馈的作用。我们的研究结果揭示了对社会和生态系统具有潜在更高和更早干旱风险的区域，并指出了当前一代气候模型中存在偏差的潜在机制。
