Core Theme 2 - Enabling and exploring new couplings between Earth system components

This core theme (CT) consists of eight workpages: WP4/5 – Coupled CH₄ cycle, WP6/7 – Coupled Nitrogen cycle and WP8/9 – Coupled dynamical ice sheets. It aims to improve how different parts of climate models are coupled together to help them perform more realistically. This means our models will be able to properly assess how interactions between the land, ocean and atmosphere affect how the climate changes in the future.

This really exciting core theme will enable brand new possibilities for our climate models to answer important questions. For example, if we want to plan how to reduce our greenhouse-gas emissions to meet climate goals, then we need to know how things like forests, permafrost and wetlands will change. We know that wetlands may produce more methane (CH₄) in future, but we are not yet able of modelling how this affects the atmosphere and the climate. We also know that nutrients, like nitrogen, run off the land into the oceans, but we do not know how this affects marine ecosystems. CT2 also looks at how ice-sheets may respond to climate change. If the huge areas of ice in Greenland and Antarctica melt then these affect global sea levels and may disrupt ocean circulation. All these effects are vital to be able to include in our models.

CT2 Leaders

Tatiana Ilyina

Earth Sytem Researcher, UNIVERSITY OF HAMBURG (Germany)

My research interests span the areas of the ocean carbon cycle, its variability, predictability, and relation to Earth’s climate. I try to tackle the fundamentals of how the ocean biogeochemical cycles act as an interactive component of the Earth system. Specifically, I investigate the extent to which these cycles can accommodate perturbations brought about by anthropogenic activities or natural forcings, as well as their influence on and response to climate variations. This is a vibrant scientific topic of increasing political and societal relevance, where I can feed by basic research directly into international processes.

I have been involved in a number of international professional activities, contributed to the IPCC's 5^th and 6^th Assessment Reports, and I co-chair the Working Group on Coupled Modelling (WGCM) of the World Climate Research Programme (WCRP).

In ESM2025, I coordinate work in CT2 and am excited about the novel science coming out of this project.

Chris Jones

Earth System Research Fellow, Met Office Hadley Centre - Exeter (United Kingdom)

I have nearly 30 years experience researching into how climate affects ecosystems and how they affect climate in return. For example, forests absorb lots of CO₂ from the atmosphere and reduce the potential impact of our emissions, but climate change might damage their ability to do this if it gets too hot or dry.

I have been a lead author on both IPCC’s 5^th and 6^th Assessment Reports, and I lead a joint project between UK and Brazil focusing on climate modelling, ecosystem resilience and climate impacts in Brazil.

In ESM2025, I planned and coordinate work in CT2.

Work Package 4/5

WP4/5 will build on developments and progress in the individual components of the models (WPs 1, 2 and 3). Our main objective is to extend the capabilities of ESMs by developing and implementing an interactive methane cycle in the ESMs.

Work Package 6/7

WP6/7 will enable a coupled simulation of reactive nitrogen and the greenhouse gas N₂O in advanced climate models (Earth system models). This is important for planning a sustainable future and to manage the nitrogen and carbon cycles optimally as far as possible.

Work Package 8/9

WP8/9 will allow new ESM capabilities by 1) coupling physical processes at the ice sheet surface with the atmosphere; 2) coupling physical processes at floating ice shelves with the ocean; 3) allowing the shape and size of the ice sheets in the climate models to change.