Black carbon is a primary aerosol emitted directly from incomplete combustion processes such as fossil fuel and forest fires. It absorbs solar radiation and the deposition of black carbon darkens snow and ice surface which reduces the albedo and therefore increases warming and could accelerate ice melting. The interaction of black carbon and cloud droplets also contributes to climate radiative forcing. Black carbon can serve as a surface where cloud droplets can form.

Studying black carbon is thus essential to better evaluate global warming.

In a recent article published in Nature communications, Zieger et al. show directly over the course of all seasons, how much black carbon can be found inside Arctic clouds. They studied the first long-term observational data set of equivalent black carbon inside and outside of clouds observed at Zeppelin Observatory, Svalbard.

Their findings indicate that the measured cloud residual black carbon concentrations exhibit a clear seasonal cycle with a maximum in early spring, due to the Arctic haze phenomenon, followed by a cleaner summer months with very low concentrations. Additionally, the study highlights that in the winter, there are less black carbon inside cloud droplets or ice crystals, probably due to mixed-phase cloud processes (when a cloud contains both liquid droplets and ice crystals). Further analysis reveals potential sources of black carbon: air masses during cloudy periods spent more time over ocean surfaces in comparison to continental regions. The study of incoming air masses suggests that anthropogenic sources of black carbon from marine sources, such as shipping or gas flaring, may play a significant role.

These findings will be essential for future model climate predictions.

> Read the paper here: https://www.nature.com/articles/s41467-023-41221-w