Over the past decades, carbon dioxide (CO2) concentrations in the atmosphere have increased rapidly, to the point that the Earth's temperature has not fully adjusted to the new warmer climate. This means that even if carbon dioxide and other greenhouse gas (GHG) emissions were instantaneously reduced to zero, the Earth would still transition to a warmer climate. In 2015, an ambitious agreement was signed in Paris to limit global warming below 2C degrees and pursue efforts to limit it to 1.5C. Global temperatures have already increased by more than 1C above pre-industrial levels. Computer simulations, used to understand what can happen to the climate in the future, have shown that delivering on the Paris Climate Agreement will require both drastic reductions of GHG emissions and use of carbon dioxide removal (CDR) strategies leading to near-zero or negative emissions by 2100. To achieve this goal, society will be required, by 2050, to remove more GHGs from the atmosphere than those released.

Afforestation/reforestation, wetland restoration, enhanced weathering and bioenergy crops are four proposed land-based CDR strategies that seek to remove CO2 in the biosphere by accelerating natural processes that are already occurring within the natural Earth cycle. These CDR strategies are recognized by the United Nations and have varying levels of technological readiness. However, unidentified environmental risks (e.g., increased non-CO2 GHG emissions) due to complex interactions between these CDR strategies, land and atmosphere are not fully understood and quantified. Therefore, while these strategies may practically remove CO2 from the atmosphere, they might not effectively stop future warming. Understanding the effectiveness of CDR efforts is critical to help society and policy makers design mitigation and adaptation approaches for tackling climate change.

This Fellowship proposes the UK first integrated study for quantifying specifically the environmental risks associated with the large-scale deployment of these four land-based CDR strategies. To address this important challenge, this Fellowship will develop a coordinated cross-disciplinary earth system science framework, which will combine new information from field experiments and surface and satellite earth observations with the next generation of computer simulations. This Fellowship will also leverage my strong interdisciplinary research background in atmosphere-biosphere-climate interactions and the expertise of internationally recognized collaborators and UK partners, the UK Government and the World Wildlife Fund to establish a world-leading group for understanding human intervention in the climate system, which will guide society and policy makers towards the most appropriate pathways to reach net-zero emissions.

Potential Impact:
Results from this UK RI Fellowship on the use of land-based CO2 removal strategies to meet climate objectives will bring important benefits to international and domestic governments, society and UK economy.

The UK Government has the commitment to "provide international leadership and lead by example in tacking climate change" and "support and protect international forests and sustainable agriculture", as outlined its 25-year Environmental Plan. The recently published UK Committee on Climate Change (CCC) Net Zero report also states that the "UK should legislate as soon as possible to reach net-zero GHG emissions by 2050". This Fellowship aligns directly with these ambitious goals, and results will feed directly into the UK Government (e.g., BEIS, DEFRA and UK CCC) when formulating strategies to achieve the grand domestic effort of decarbonisation and improving the environment.

At an international level, the Fellowship is directly linked to the World Climate Research Program Grand Challenges in "Carbon Feedbacks in the Climate System" and to the United Nations (UN) Sustainable Development Goals (SDGs) of "Climate Action" and "Life on Land". The UN identified 17 SDGs with the objective of transforming the world for the better by 2030. Research results from this Fellowship will also feed directly into the upcoming IPCC reports, which will inform the UN Framework Convention on Climate Change (UNFCC) discussions and policy.

Under the UNFCC umbrella, the Paris Agreement was adopted in 2015, in which over 190 countries committed to establish a global action plan to stop climate change by limiting global warming to well below 2C and pursuing efforts to limit it to 1.5C. There is a strong commitment from many nations in the world to use land management to mitigate climate change. For example, the global Bonn Challenge plans to bring 150 million hectares of deforested and degraded land into restoration by 2020 and 350 million hectares by 2030; the UN programme on Reducing Emissions from Deforestation and Forest Degradation in Developing Countries (REDD+). As a part of Paris Agreement ratification, countries are required to submit Intended Nationally Determined Contributions (INDCs) and later Nationally Determined Contributions (NDCs). The INDC/NDCs describe each country's plan to mitigate and adapt to future climate change, and some INDC/NDCs depend on strong land-based mitigation strategies. This Fellowship will help quantify the climate benefits associated with the land-use aspect of these action plans and will be of relevance to the governments that have set ambitious land-use targets (e.g. Brazil and China) and to those that are planning to do so.

Thus, this Fellowship will provide information relevant for policy implementation at many levels: in the UK (e.g., new policies post-brexit), in Europe (e.g., 2030 Climate and Energy Framework), and in the world (e.g., UNFCC, REDD+).

There are many national and international charities and NGOs campaigning for climate change mitigation and more sustainable forest and agriculture management, and wildlife conservation (e.g. WWF, EarthWatch, etc). This Fellowship will provide research results that can be transformed into information align within their work.

This Fellowship will also deliver an improved domestic earth system model, UK-ESM, which will feed back directly into the weather and climate prediction models at the MetOffice. These forecasting models are used operationally to provide weather forecast and climate projections. Future climate change will require mitigation and adaptation strategies, with immense costs to the society. Improved accuracy in climate projections will help ensure that resources are maximized and thus also contribute to the UK economic success.