FORCeS - Constrained aerosol forcing for improved climate projections

FORCeS will improve the description of key processes governing aerosol radiative forcing and feedbacks in climate models.

The Paris Agreement central aim is to keep the global temperature rise this century well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5 degrees Celsius. The actions needed to reach this goal, and the urgency and effectiveness of their implementation, rely crucially on accurately predicting the time-evolution of radiative forcing and the resulting climate response. Uncertainty in simulating the components of the atmosphere, especially those related to aerosol, clouds and their interactions hampers our ability to understand the past and project future climate change. This is because anthropogenic aerosols exert a net cooling impact on climate that offsets – but with large uncertainty - part of the warming effect from greenhouse gas emissions.

To resolve the above challenge FORCeS will substantially increase the confidence in estimates of aerosol radiative forcing and its impact on transient climate response. FORCeS will do this by bridging a crucial gap that currently exists between knowledge on the process scale and model application on the climate scale. FORCeS will identify, observationally constrain and efficiently parameterize the most important processes driving aerosol radiative forcing. With this knowledge, FORCeS will produce more robust estimates of the overall aerosol contribution to past climate change, leading to tighter constraints on climate sensitivity, and ultimately more accurate projections of the near-term climate change. Based on the scientific knowledge gained, FORCeS will inform decision and policy makers about the effect of aerosol emission changes on regional and global climate evolution and on emission pathways to meet the targets of the PA.

The knowledge gaps addressed in FORCeS, expected outcomes, and contribution to objectives.

Project Goals

The primary aims of FORCES are:

1. Identify the most important cloud and aerosol processes or components controlling radiative forcing and transient climate response. Make targeted improvements of the corresponding parameterizations for a set of leading European climate models, to obtain more reliable transient climate simulations.

2. Exploit models, statistical methods, data mining and the recent wealth of observations to reduce the uncertainty in anthropogenic radiative forcing associated with aerosols and aerosol-cloud interactions from more than ±100% (2) to closer to ±50%.

3. Quantify the near-term climate impact and associated uncertainty ranges for a set of plausible combinations of near-term greenhouse gas and aerosol emission pathways, in support of the PA.

Role of SMHI

SMHI co-leads Work Package (WP) 5 - Climate response and feedbacks and WP7 - User engagement, communication and dissemination. SMHI will also contribute scientifically to WPs 5 (through EC-Earth simulations on mechanisms and feedbacks related in particular to Arctic climate change), and 6 (through EC-Earth simulations on transient climate response and prediction).

Project partners

FORCES, led by Ilona Riipinen and Annica Ekman from Stockholm University, brings together 20 institutions from 12 European countries. The complete list of project partners can be found here.


FORCES is a European Union Horizon 2020 Project funded under the program LC-CLA-08-2018 - Addressing knowledge gaps in climate science, in support of IPCC reports under grant agreement No 821205.


FORCES will run from October 2019 to September 2023.

Contact person at SMHI

Klaus Wyser