Meeting the Paris Agreement on Climate: Exploiting Earth System Models to determine the role of future land-use change

This Fellowship will exploit the next generation of climate models to make the UK's first assessment of the potential for land-use change policy (e.g., reduced deforestation and increased afforestation) to help society meet climate targets.

Three years ago, an ambitious global agreement was signed in Paris to try and limit warming due to climate change to less than 2 degrees since the pre-industrial period; we're already at almost 1 degree. Scientists can use detailed computer simulations to try and understand what could happen to the climate in the future; by 2050 in scenarios that succeed in limiting warming to the levels specified in the Paris Agreement, society is no longer a net emitter of greenhouse gases (GHGs), but we are drawing more GHGs out of the air than we're putting in. The longer it takes global GHG emissions to peak the greater the extent of GHG removal, or negative emissions, we will require. There are a couple of ways that net negative emissions could be achieved. Currently, the most technologically feasible is through eliminating deforestation and engaging in large-scale afforestation and reforestation. Another way, which relies on future technological developments, is to burn biomass to generate energy and then capture and store any GHGs that would have been emitted in deep geological reservoirs. Initial estimates suggest that an area the size of Australia would need to be dedicated to growing energy crops in order to generate sufficient negative emissions through this process.

My previous research has demonstrated that forests and other vegetation can have a cooling impact on the climate because of interactions between plants and the composition of the atmosphere. Plants emit a wide range of gases into the air, the kind that give pine forests their distinctive smell. These gases take part in complex chemical reactions and can go on to form particles that act as seeds for cloud droplet formation. This process is important because the more droplets there are in a cloud, the brighter and more reflective of the Sun's energy it is, helping to cool the climate. My previous work also indicates that the cooling effects due to these natural particles could become stronger as global temperatures rise; this may act to slightly dampen the warming caused by higher GHG concentrations.

During my Fellowship, I will develop and use the UK's first fully-coupled Earth System Model (UKESM) to assess the potential for future land-use change to help meet global climate targets. I will work with international organisations to ensure that UKESM contains state-of-the-science understanding of biosphere-atmosphere interactions; using a fully-coupled ESM to explore this represents a step-change in the way we can evaluate impacts on, and of, future climate.

The United Nations (UN) has identified 17 Sustainable Development Goals (SDGs) which aim to transform the world by 2030; among them is Goal 13: "Take urgent action to combat climate change and its impacts". In 2015, the 21st Conference of the Parties of the UN Framework Convention on Climate Change (UNFCCC) resulted in the Paris Agreement which describes a collective goal to limit warming to "well below 2 degrees" and to "pursue efforts to limit ... to 1.5 degrees". Research results from my Fellowship will feed directly into future Intergovernmental Panel on Climate Change (IPCC) Assessment Reports that inform UNFCCC discussions and policy.

In conjunction with the Paris Agreement on Climate, countries around the world prepared Intended Nationally Determined Contributions (INDCs) to state what they would do to mitigate, and adapt to, future climate change. These INDCs transition to become Nationally Determined Contributions (NDCs) once a country ratifies the Paris Agreement and are to be reviewed and revised every five years. Many of the INDCs/NDCs assume a substantial contribution for land-use change in meeting the climate mitigation targets set by individual countries. My research will quantify the climate benefits associated with the land-use component of the INDC/NDCs and will therefore be of direct relevance to the governments of individual countries, both those who have set ambitious land-use targets (e.g., Brazil, China) and those who are yet to do so.

In January 2018, the UK government outlined its commitment to "provide international leadership and lead by example in tackling climate change" and to "support and protect international forests" in its 25-year Environment Plan. My research on the global climate impacts of future land-use change will therefore be of use to UK government (both the Department for Business, Energy and Industrial Strategy (BEIS) and the Department for Environment, Food and Rural Affairs (Defra)) when formulating strategies designed to achieve this.

There are many national and international charities and NGOs campaigning for more sustainable management of the world's forests (e.g., World Wildlife Foundation, United Bank of Carbon, International Tree Foundation, Plan Vivo). My research findings will provide a scientific underpinning for the work they do and guide decisions about parts of the world in which to focus these efforts.

The developments I make to the UK's Earth System Model during this Fellowship will feed back directly into, and help to improve, the Met Office family of weather and climate prediction models. This family of models are used operationally to provide local, regional and global weather forecasts, as well as longer term climate projections. The general public and many UK services benefit from accurate weather forecasts provided by the Met Office with the estimated economic value of these forecasts in excess of £500 million per year. Mitigating, and adapting to, future climate change will have huge costs to society; improved accuracy in climate projections can help to ensure that resources are maximised.