Constrained aerosol forcing set to improve climate projections
The Paris Agreement on climate change stipulates that countries must endeavour to limit global warming from anthropogenic activities to within 2 °C above pre-industrial levels. However, meeting this goal requires being able to accurately predict the time evolution of radiative forcing, or the change in the atmosphere’s energy balance, and the impact this change has on the climate. “Uncertainty in simulating the atmosphere’s components, especially those related to aerosol, clouds, and their interactions, has hampered our ability to understand past and project future climate change,” says Ilona Riipinen, director of the Bolin Centre for Climate Research at Stockholm University. With the support of the EU-funded FORCeS project, Riipinen is working to change this. “Our aim with this project was to better understand and reduce the uncertainty in the climate forcing associated with aerosol-cloud-climate interactions,” she adds.
How aerosol changes can offset the warming caused by greenhouse gas emissions
Anthropogenic aerosols have a net cooling impact on the climate, one that offsets part of the warming caused by greenhouse gas emissions. The challenge is that the magnitude of this impact is not as well-known as, for example, the warming impact of greenhouse gases. “Accurate estimates of the time we have left for reducing greenhouse gases to achieve our climate targets require robust quantification of the climate forcing associated with aerosols,” explains Riipinen. Aerosol emissions are expected to substantially decrease in the coming decades, resulting in a warming effect. “It is therefore crucial to establish the extent to which aerosol changes – whether due to anthropogenic emissions or as feedback induced by warming – offset or amplify the warming caused by greenhouse gas emissions,” notes Riipinen.
Improving climate models
To help provide this information, FORCeS researchers identified the most important cloud and aerosol processes and components controlling radiative forcing and transient climate response. “One of our key focuses was on making the targeted improvements to a set of leading European climate models needed to obtain more reliable climate simulations,” remarks Riipinen. Furthermore, by exploiting available models, statistical methods, data and observations, the project increased the confidence in estimates of anthropogenic radiative forcing associated with aerosols and aerosol-cloud interactions. “We also quantified the near-term climate impact and associated uncertainty ranges for a set of plausible combinations of near-term greenhouse gas and aerosol emission pathways,” says Riipinen.
On the right path towards achieving our climate objectives
The FORCeS project has successfully advanced our fundamental understanding of aerosol-cloud-climate interactions and improved leading European climate models in terms of their representation of aerosols and clouds. It also made new assessments of the role of aerosols and clouds in past and future climate evolution. “Although there’s more work to be done, our research helps keep us on the right path towards achieving our ambitious climate objectives,” concludes Riipinen. The project has published over 200 original peer-reviewed articles, three policy briefs, and openly available scientific summary reports and data sets. The research team now continues to work on integrating all the scales relevant for aerosol-cloud-climate interactions.
Keywords
FORCeS, climate projections, aerosol, climate change, radiative forcing, greenhouse gas emissions
