The Net-Zero Emissions Challenge: Quantifying unintended climate feedbacks from large-scale deployment of land-based CO2 removal strategies

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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.