Snow is a crucial component of the cryosphere and its has been experiencing a significant decline for the Northern Hemisphere (NH) (35–90N) snow cover extent (SCE) in March-April over the 1948–2012 period. However, the causes of this historical snow cover decline are still uncertain. Here, based on the Global Land Data Assimilation System version 2.0 (GLDAS) reanalysis reanalyzed snow cover extent (SCE) and climate model simulations that separate different anthropogenic forcings, we attribute changes of spring SCE over the NH to anthropogenic and natural climate forcings using an optimal fingerprint technique. We find that fingerprints from greenhouse-gases (GHG) and stratospheric aerosols can be clearly detected in the historical SCE records, whereas natural forcing has not contributed to the long-term SCE trend in a discernible way. The GHG-induced warming is primarily responsible for the NH SCE decline, which, however, has been partly offset (by ∼16%) by aerosol-induced climatic cooling. Our findings confirm the negative effect of warming on SCE changes yet highlight the positive role of aerosols in slowing SCE decline over the past 65 years.

雪是冰冻圈的重要组成部分，在 1948 年至 2012 年期间，北半球（NH）（35-90N）积雪范围（SCE）在 3 月至 4 月期间经历了显着下降。然而，这种历史积雪减少的原因仍然不确定。在这里，基于全球土地数据同化系统 2.0 版 (GLDAS) 再分析重新分析积雪范围 (SCE) 和区分不同人为强迫的气候模型模拟，我们将 NH 上春季 SCE 的变化归因于人为和自然气候强迫最佳指纹技术。我们发现在历史 SCE 记录中可以清楚地检测到来自温室气体 (GHG) 和平流层气溶胶的指纹，而自然强迫并没有以可辨别的方式对长期 SCE 趋势做出贡献。GHG 引起的变暖是 NH SCE 下降的主要原因，但是，气溶胶引起的气候冷却部分抵消了（约 16%）。我们的研究结果证实了变暖对 SCE 变化的负面影响，但强调了过去 65 年气溶胶在减缓 SCE 下降方面的积极作用。