Aerosol particles cool the climate by scattering solar radiation and by acting as cloud condensation nuclei. Higher temperatures resulting from increased greenhouse gas levels have been suggested to lead to increased biogenic secondary organic aerosol and cloud condensation nuclei concentrations creating a negative climate feedback mechanism. Here, we present direct observations on this feedback mechanism utilizing collocated long term aerosol chemical composition measurements and remote sensing observations on aerosol and cloud properties. Summer time organic aerosol loadings showed a clear increase with temperature, with simultaneous increase in cloud condensation nuclei concentration in a boreal forest environment. Remote sensing observations revealed a change in cloud properties with an increase in cloud reflectivity in concert with increasing organic aerosol loadings in the area. The results provide direct observational evidence on the significance of this negative climate feedback mechanism.

气溶胶颗粒通过散射太阳辐射和充当云凝结核来冷却气候。有人认为，温室气体水平增加导致的气温升高会导致生物二次有机气溶胶和云凝结核浓度增加，从而形成负气候反馈机制。在这里，我们利用并置的长期气溶胶化学成分测量和对气溶胶和云特性的遥感观测，对这种反馈机制进行直接观察。夏季有机气溶胶负荷随着温度的升高而明显增加，同时北方森林环境中云凝结核浓度也增加。遥感观测揭示了云特性的变化，云反射率的增加与该地区有机气溶胶负荷的增加相一致。结果为这种负气候反馈机制的重要性提供了直接的观测证据。