How much atmospheric change is due to human aerosol emissions?

Anthropogenic aerosols are small particles which are emitted into the atmosphere along with greenhouse gases through fossil fuel emissions. Like greenhouse gases they are considered a climate forcing, i.e., something which causes a disruption to Earth's energy budget. However, while greenhouse gas concentrations in the atmosphere continue to increase, global aerosol emissions have been decreasing since the 1980s due to air quality measures, and are expected to decrease further in the future.

The climate of the future will be determined largely by the response to these two forcings - aerosol emissions and greenhouse gas concentrations. One of the best ways this can be evaluated is to determine how much of the observed past climate change (e.g., global warming) can be attributed to the influence of the individual forcings. This knowledge can then be used to improve future predictions.

To estimate the contribution of individual forcings so called 'Detection & Attribution methods' are applied. These methods have been used to reliably estimate the overall anthropogenic impact (i.e., both aerosols and greenhouse gases combined) on the climate system, but it can be difficult to separate the individual contributions  because the two forcing often occur in the same space at the same time. Thus, to improve the estimation of the impact anthropogenic aerosols have on the climate system we are using the distinct effect the individual forcings have on temperature and precipitation to separate between the aerosol and greenhouse gas signals. Further, we are using novel machine learning methods to investigate how the detected changes are causally linked and the effect they have on extreme events, such as heavy precipitation or drought.