导 读
2023年春季北京经历了11天的沙尘天气。为什么在大范围造林的努力下，沙尘天气仍然频繁发生甚至比过去更多？统计分析结果显示：蒙古国的沙尘源占比近90%。蒙古国作为我国北方的主要沙源地，近年来频繁遭受热浪和干旱的侵袭，正在陷入“更暖、更干”的恶性反馈中，已对我国北方生态安全造成严重威胁。
得益于生态恢复工程和气候变化的共同作用，近70年来北京沙尘天气的平均观测天数呈总体下降的趋势。然而，2023年3–4月，北京却遭遇了11天的沙尘天气（图1），是过去五年平均沙尘天数的近三倍。为什么在大规模植树造林的努力下，沙尘天气仍然频繁发生，甚至比过去更多？云南大学陈文教授团队最新的研究指出：蒙古高原—东亚沙尘的主要源区之一，起到了至关重要的作用。统计分析表明：2023年北京出现的11天沙尘天气中，有10天的沙尘源来自蒙古。
图1 2023年发生在北京的11次沙尘天气的后向轨迹示意图。该轨迹基于HYPLIT模式（https://www.ready.noaa.gov/hypub-bin/trajsrc.pl)。
在过去20年里，蒙古高原频繁遭受极端热浪和干旱影响，植被覆盖减少、土壤表面裸露，为沙尘天气提供了足够的沙源。此外，异常活跃的蒙古气旋能够将大量沙尘输送至我国北方，导致沙尘天气的发生。多项研究结果表明蒙古高原很可能正在陷入“更暖、更干”的恶性反馈中。
随着全球平均气温的持续上升，蒙古高原的升温相比于其他区域更加显著。同时，近十余年来蒙古高原的降水量大幅下降。在高温和少雨的共同影响下，蒙古高原在21世纪初之后遭受了极为罕见的严重干旱。干燥的土壤促使热量直接加热周围的空气，由此产生的高温导致土壤更加干燥。这种正反馈正在重塑蒙古高原的气候，并很有可能将其推向不可逆转的干-热状态。
雪上加霜的是，人为活动进一步加剧了蒙古高原水资源短缺和生态环境退化。自20世纪90年代以来，蒙古国社会经济高速发展，作为支柱产业的畜牧业和矿业蓬勃发展。国际货币基金组织最近的一份报告显示：从1990年到2020年，蒙古国的牲畜数量增长了三倍，已经远远超过了草原的承载能力。高温、干旱和过度放牧导致的土地退化共同推动了蒙古国荒漠化和沙尘暴的急剧发展。随着境内近70%草原覆盖的退化，相比20世纪60年代，蒙古国每年观测到的沙尘暴天数近些年增加了三倍以上。生态恶化态势异常严峻，如果没有积极有效的行动，类似2023年这样异常频繁的沙尘天气，在将来就可能成为常态，而且“三北防护林项目”等各种国家项目的效用也将大打折扣。
该研究强调：亟需采取行动，减缓和适应蒙古高原的极端气候变化。一个有效的策略是：提高公众对极端天气事件的健康防范意识并建立紧急救援系统。同时，为减缓人类活动的影响，加强沙尘源区的荒漠化治理势在必行，包含调整产业结构、推广可持续发展产业以及改进畜牧业和矿业的关键技术。最后，呼吁推动更深入的国际合作，加快适应气候变化的进程。
总结与展望
该研究以2023年春季我国北方沙尘天气异常频发的现象为切入点，指出了蒙古高原作为主要沙尘源区的关键作用，并着重强调了该区域日益严峻的气候和生态危机。在气候变化和人类活动的共同影响下，蒙古高原近20年来频繁遭受极为罕见的高温和干旱侵袭，很可能已陷入“更暖、更干”的正反馈中，将对气候和生态安全造成不可逆转的严重后果。基于此，亟需积极推动国际合作并采取积极有效的措施减缓和适应上述极端气候变化。
责任
高 贵 西南交通大学
本文来自
Cell Press合作期刊
The Innovation第四卷第五期以Commentary发表的“Increased sandstorm frequency in North China in 2023: Climate change reflection on the Mongolian plateau” (投稿: 2023-05-08；接收: 2023-08-10；在线刊出: 2023-08-11)。
DOI: https://doi.org/10.1016/j.xinn.2023.100497
引用格式：Piao J., Chen W., Wei K., et al. (2023). Increased sandstorm frequency in North China in 2023: Climate change reflection on the Mongolian plateau. The Innovation 4(5), 100497.
简介
陈 文，云南大学特聘教授（二级），博士生导师，国家杰出青年科学基金获得者，国家自然科学基金创新研究群体项目负责人，科技部重点研发“全球变化与应对”专项首席科学家，入选国家百千万人才工程并被授予“有突出贡献中青年专家”荣誉称号。陈文教授长期从事东亚季风研究，曾长期担任中国科学院大气物理研究所季风系统研究中心主任。在国内外学术刊物上发表论文400余篇，含SCI论文300余篇，论文被SCI引用12000余次。
http://www.srees.ynu.edu.cn/info/1454/3941.htm
魏 科，博士，中国科学院大气物理研究所研究员，中国科学院青年创新促进会会员，主要从事平流层-对流层相互作用、东亚季风和极端天气气候变化等方面的研究。负责和参与国家自然科学基金、中俄国际合作、俄乌白国际合作、国家重点基础研究发展计划、中国-联合国环境署国际合作项目、中国-以色列国际合作项目等多个研究项目。担任北京陶诗言气象发展基金会科普大使、青年科学家社会责任联盟理事、中国科协科技工科技/科普专家、中国气象服务协会气象科技与信息教育专家委员会委员、科教版《科学》课审稿专家及科学顾问等职务。
https://people.ucas.edu.cn/~weike
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