Periodic Reporting for period 3 - FORCeS (Constrained aerosol forcing for improved climate projections)
Reporting period: 2022-10-01 to 2024-03-31
Atmospheric aerosol particles, i.e. liquid and solid particles in air, influence Earth’s climate and impact air quality. The overall objective of FORCeS was to understand and reduce the long-standing uncertainty of the effects of anthropogenic aerosol particles on climate, which is crucial for increasing confidence in climate projections. These projections provide a basis for mitigation planning and inform on emission pathways that will facilitate achieving the targets of the Paris Agreement (PA). FORCeS brought together leading European scientists with trans-disciplinary expertise to i) exploit in-situ and remote sensing atmospheric data that have emerged during the recent decades; ii) perform dedicated laboratory and field experiments; iii) utilize a range of state-of-the-art computational models; and iv) apply novel theoretical methods including machine learning techniques. The process analysis within FORCeS was synthesized to improve a set of leading European climate models, providing essential information to climate assessments such as reports by the Intergovernmental Panel on Climate Change (IPCC). The knowledge gap between process scale and model application on the climate scale has been one of the main reasons preventing the climate science community to push the frontier in understanding aerosol-cloud-climate interactions. FORCeS bridged this knowledge gap systematically, by constraining processes on scales ranging from hours to decades, leading to the desired refinement of model-estimated aerosol radiative forcing and climate sensitivity. To communicate FORCeS science and ensure maximum impact, FORCeS reached out to decision-makers and stakeholders and provided added-value information through e.g. workshops where climate science and climate policy experts met and interacted.
FORCeS has reached its overarching goals as it has contributed to understanding and reducing the uncertainty in estimates of aerosol-cloud-climate interactions. FORCeS provided new knowledge on the behavior of key aerosol components (organic compounds, nitrate, light-absorbing components) and processes (ultrafine aerosol dynamics, interactions with clouds), as well as cloud processes (interaction with aerosol particles, microphysics cloud droplets and precipitation formation as well as ice formation in the atmosphere). FORCeS used this improved understanding to evaluate and develop leading Earth System Models (ESMs), which form the methodological basis for future projections e.g. discussed by the IPCC. To evaluate and constrain the model predictions, FORCeS collected observational data over various scales and developed robust theories for interpreting the observations. To fill key gaps in observational constraints, novel laboratory experiments and field campaigns (in e.g. the Arctic, boreal, and central European environments) were completed successfully, and detailed models were used to develop new process-based metrics and constraints for ESM evaluation. Historical aerosol loadings and sophisticated statistical methods were used together with present-day observations to highlight the most important revisions needed in the ESMs, and to derive constraints on Earth’s climate sensitivity. Novel approaches and tools for evaluating ESMs were developed and used to pinpoint important areas for future model development. The research output from FORCeS in the form of publications and conference presentations has been substantial, and targeted efforts were made in the final period to ensure efficient dissemination and communication of the project results to the relevant audiences, in the form of e.g. conference presentations, workshops, policy briefs and news articles on the FORCeS website. In summary, FORCeS reached its objectives and made targeted efforts to ensure effective dissemination and legacy of the project outcomes.
The key outcomes from the FORCeS project include:
i. New fundamental understanding of physical and chemical processes involving aerosols and clouds;
ii. Climate models with new and improved descriptions of aerosols and aerosol-cloud interactions;
iii. Improved predictions of climate evolution in the context of climate policy, particularly the PA;
iv. Improved quantification and reduction of uncertainty related to aerosol radiative forcing, climate sensitivity and transient climate response.
FORCeS successfully reached the anticipated outcomes. All the planned laboratory and field experiments were completed, despite the COVID-19 pandemic, and the results were published in open-access archives and publications. These observations provide unique and novel insights into aerosols and aerosol-cloud interaction processes. Based on the fundamental knowledge, we have made concrete recommendations on the representation of key components and processes governing aerosol forcing in ESMs and developed new parameterizations for missing key processes. The recommendations and parameterizations were implemented in the FORCeS ESMs and used to provide new estimates of the near-term climate evolution. Several new and complementary approaches to constraining equilibrium climate sensitivity (ECS) and transient climate response (TCR) – i.e. measures that are central for climate projections and hence steps towards meeting the PA targets – have emerged from FORCeS. The new constraints show an increased probability of TCR and ECS values in the upper range of the IPCC AR6 estimates.
The objectives of FORCeS were designed to meet the following impacts:
i. Supporting major international scientific assessments;
ii. Increase confidence in climate projections;
iii. Providing added value to decision- and policymakers;
iv. Sustaining Europe’s leadership in climate science.
FORCeS delivered results that ensure its targeted impacts. FORCeS outcomes have been included in past assessments such as those by the IPCC AR6 and the Arctic Monitoring and Assessment Program (AMAP), and the project has delivered updated ESMs that will be used in the upcoming IPCC AR7. Furthermore, FORCeS took strategic steps towards enhancing the dialogue between different aerosol-cloud-climate research communities and summarized recommendations on the treatment of key aerosol and cloud processes in ESMs. Together with the above work, these efforts will lead to the desired increased confidence in climate projections. In dialogue with stakeholders, FORCeS delivered three policy briefs (“Is there a conflict between the clean air goals of the European Green Deal and climate neutrality”, “Air quality and climate policies: Moving forward after COVID-19”, and “Aerosol impacts on regional climate”), which have framed their questions in the context of the PA. The knowledge has been disseminated from the FORCeS community to relevant policymakers through workshops and media channels. From a wider perspective, FORCeS provided essential information for developing cost-effective multi-beneficial abatement strategies, providing better health and resilient food production, in support of several of the United Nations’ Sustainable Development Goals. The novel and innovative methods applied in FORCeS to evaluate the performance of ESMs will lead to further improvements of these models. Together with educating and mentoring a cohort of active Early Career Researchers, FORCeS has promoted and sustained Europe’s leading position in climate science.
i. New fundamental understanding of physical and chemical processes involving aerosols and clouds;
ii. Climate models with new and improved descriptions of aerosols and aerosol-cloud interactions;
iii. Improved predictions of climate evolution in the context of climate policy, particularly the PA;
iv. Improved quantification and reduction of uncertainty related to aerosol radiative forcing, climate sensitivity and transient climate response.
FORCeS successfully reached the anticipated outcomes. All the planned laboratory and field experiments were completed, despite the COVID-19 pandemic, and the results were published in open-access archives and publications. These observations provide unique and novel insights into aerosols and aerosol-cloud interaction processes. Based on the fundamental knowledge, we have made concrete recommendations on the representation of key components and processes governing aerosol forcing in ESMs and developed new parameterizations for missing key processes. The recommendations and parameterizations were implemented in the FORCeS ESMs and used to provide new estimates of the near-term climate evolution. Several new and complementary approaches to constraining equilibrium climate sensitivity (ECS) and transient climate response (TCR) – i.e. measures that are central for climate projections and hence steps towards meeting the PA targets – have emerged from FORCeS. The new constraints show an increased probability of TCR and ECS values in the upper range of the IPCC AR6 estimates.
The objectives of FORCeS were designed to meet the following impacts:
i. Supporting major international scientific assessments;
ii. Increase confidence in climate projections;
iii. Providing added value to decision- and policymakers;
iv. Sustaining Europe’s leadership in climate science.
FORCeS delivered results that ensure its targeted impacts. FORCeS outcomes have been included in past assessments such as those by the IPCC AR6 and the Arctic Monitoring and Assessment Program (AMAP), and the project has delivered updated ESMs that will be used in the upcoming IPCC AR7. Furthermore, FORCeS took strategic steps towards enhancing the dialogue between different aerosol-cloud-climate research communities and summarized recommendations on the treatment of key aerosol and cloud processes in ESMs. Together with the above work, these efforts will lead to the desired increased confidence in climate projections. In dialogue with stakeholders, FORCeS delivered three policy briefs (“Is there a conflict between the clean air goals of the European Green Deal and climate neutrality”, “Air quality and climate policies: Moving forward after COVID-19”, and “Aerosol impacts on regional climate”), which have framed their questions in the context of the PA. The knowledge has been disseminated from the FORCeS community to relevant policymakers through workshops and media channels. From a wider perspective, FORCeS provided essential information for developing cost-effective multi-beneficial abatement strategies, providing better health and resilient food production, in support of several of the United Nations’ Sustainable Development Goals. The novel and innovative methods applied in FORCeS to evaluate the performance of ESMs will lead to further improvements of these models. Together with educating and mentoring a cohort of active Early Career Researchers, FORCeS has promoted and sustained Europe’s leading position in climate science.