Objectives

The primary goal of OptimESM is to develop the next generation of ESMs, bringing together increased model resolution and process realism, and to deliver long-term climate projections that better support policy andsocietal needs, providing guidance on regional climate change at different levels of global warming, the risk of abrupt Earth system changes at these warming levels and the regional impacts arising from such events.

This primary goal will be realised through the following objectives:

Objective 1: To develop the next generation of ESMs through an optimal combination of increased model resolution and representation of key physical and biogeochemical processes, leading to the best exploitation of available and future computing resources

Objective 2: To exploit new and existing observations to evaluate and constrain ESM simulations, including the provision of uncertainty estimates, identification of abrupt climate change indicators and an improved understanding of processes underpinning these abrupt changes.

Objective 3: To develop and deliver new policy relevant emission scenarios extending to 2300, ready for use in ESMs including ones based on current policies and the most recent Nationally Determined Contributions (NDCs), ones that realise the Paris Agreement, that temporarily overshoot the Paris targets and that stabilise at different levels of global warming.

Objective 4: To deliver new ESM projections beyond 2100 sampling the range of new emission scenarios.

Objective 5: To increase our understanding of potential tipping points in the Earth system, such as ice sheets, Arctic sea ice, ocean circulation, permafrost, and marine and terrestrial ecosystems, and improve our ability to attribute such events to driving processes and levels of global warming.

Objective 6: To deliver high-resolution information on the impact of abrupt climate change and different levels of stabilized global warming on regional climate change, including extreme events.

Objective 7: To ensure a strong European contribution to the international research agenda, including the 7^th Coupled Model Intercomparison project (CMIP7) and the WCRP Lighthouse activities Safe Landing Climates and Explaining and Predicting Earth System Change.

Objective 8: To provide policy guidance on the feasibility of realising the Paris climate targets and the consequences of overshooting these targets, including regional impacts and the risk of triggering Earth system tipping points.

Objective 9: To explore to what extent the exceedance of critical tipping points is associated with impacts on selected socio-economic activities (e.g., human health, water and energy resource management) and to facilitate a comprehensive framework for assessing such socio-economic impacts under different levels of global warming, considering the risk of abrupt Earth system changes.