Satellite-derived products and reanalyses show consistent increases in downward surface solar radiation (SSR) and decreases in cloud cover over North America and Europe from the 1980s to 2010s. These trends show a strong seasonality, with the largest changes in boreal summer. A set of timeslice experiments with an atmospheric general circulation model (AGCM) forced with prescribed changes in sea surface temperature/sea ice extent (SST/SIE), greenhouse gas (GHG) concentrations, and anthropogenic aerosol (AA) emissions, together and separately, is performed to assess the relative roles of different forcings in these observed trends. The model reproduces the main observed features over Europe and North America, including the seasonality of trends, suggesting a dominant role of forced changes in the recent trends in SSR and cloud cover. Responses to individual forcings indicate that recent decadal trends in SSR over Europe are predominantly driven by AA emission reductions, with an additional influence from SST/SIE and GHG changes. In contrast, changes in AA, SST/SIE, and GHG contribute more equally to simulated decadal trends in SSR and cloud cover over North America, although SST/SIE play the most important role. In our simulations, responses of SSR to AA emission reductions are primarily governed by aerosol-radiation interactions. Responses to SST/SIE and GHG changes are predominantly due to cloud cover changes, which are driven by atmospheric circulation and humidity changes. This process level understanding of how different forcing factors influence decadal trends in SSR and cloud cover is valuable for understanding past changes and future projections in global and regional surface energy budgets, surface warming, and global and regional hydrological cycles.

卫星衍生产品和再分析显示，从 1980 年代到 2010 年代，北美和欧洲的向下表面太阳辐射 (SSR) 持续增加，而云量减少。这些趋势显示出强烈的季节性，北方夏季的变化最大。一组使用大气环流模型 (AGCM) 的时间片实验，强制海面温度/海冰范围 (SST/SIE)、温室气体 (GHG) 浓度和人为气溶胶 (AA) 排放的规定变化，一起和单独, 用于评估不同强迫在这些观察到的趋势中的相对作用。该模型重现了欧洲和北美的主要观测特征，包括趋势的季节性，表明强制变化在近期 SSR 和云层覆盖趋势中起主导作用。对个别强迫的响应表明，最近欧洲 SSR 的十年趋势主要由 AA 减排驱动，另外还有 SST/SIE 和 GHG 变化的影响。相比之下，AA、SST/SIE 和 GHG 的变化对北美 SSR 和云层覆盖的模拟年代际趋势的贡献更为平均，尽管 SST/SIE 起着最重要的作用。在我们的模拟中，SSR 对 AA 减排的响应主要受气溶胶-辐射相互作用的控制。对 SST/SIE 和 GHG 变化的响应主要是由于云量变化，而云量变化是由大气环流和湿度变化驱动的。