Special edition compiled in partnership with Frontiers sponsored by the Clean Air Task Force. The realisation of Net Zero by 2050 will require the ability for strategy developers, operational planners and decision makers to better manage uncertainty, complexity and emergence. The application of the orthodox set of decision support tools and processes that have been used to explore deep decarbonisation options to 2050 have blinded decision makers to uncertainty, complexity and emergence. Tools have often been used which are inappropriate to the types of decisions being made – a competency which has been glaringly revealed during the C-19 Pandemic. This Frontiers Research Topic will highlight the need for an interdisciplinary, mixed methods approach bringing together insights from modelling, decision science, psychology, anthropology, and sociology to form a compendium of current best practice for decision making for the net zero transformation and new research frontiers. Develop greater awareness amongst policymakers, practitioners and academics as to the importance of: • Understanding the nature of uncertainty when dealing with problems associated with the Net Zero Energy System Transformation; • Increasing importance of deliberative processes to map different value sets beyond least cost; • Acknowledging that decision making under uncertainty requires competency-based training leading to a full appreciation of the tasks at hand. Suggested areas within scope are listed in points 1-12 below. Authors are free to choose specific areas of interest, and to combine these where useful. In general, it will be useful to consider practical application of [ideas], e.g • development of `Use Cases’ and `Decision Making Contexts’ may be useful, e.g. National Govt establishing its Carbon Budget; Institution setting up its investment portfolio. • understanding of how decisions are being made within different jurisdictions, political cultures, and types of organizations (public/private). What is the role of `Decision Context' i.e. organisational decision-making structures, cultures, the role of zeitgeist and dominant narratives, or the relation between academic expertise and policy-makers. 1. Decision making from an end-to-end perspective and the need to take a holistic and interdisciplinary perspective [Editorial Cover Article]. 2. Gap between what policy makers and decision makers around net zero climate policy seek to address and what decision support tools can actually do. Why that gap is increasing (if it is)? 3. Understanding the nature of uncertainty when applying the relevant decision support tool and processes. Not all uncertainty can be addressed within the decision support tool itself. Role of optimism bias; potential role of least worst regret approaches etc 4. What different decision support tools can inform decision makers around net zero climate policy and need for a basket of tools. 5. Why parametric decision support tools and models are pre-eminent - the role of consolidative modelling and exploratory modelling. The inertia of modelling approaches: why it is so hard to break modelling paradigms? 6. What decision science informs us about how decisions are actually made - the importance of process, the role of transparency and deliberation with analysis. 7. Processes that address the biases identified in decision science and impact of identity politics on deliberative decision making. 8. Why decision making under deep uncertainty requires competency-based training, deep subject matter expertise and systemic knowledge. 9. Ministerial and policy making and the decision support requirements: US, EU, UK & China 10. The role of narratives and how uncertainty can be communicated to societal audiences. Storylines and other narrative approaches 11. How to develop participatory approaches allow multiple values, diversity of stakeholders in which climate communication and decision making exists in an iterative exchange with policy. We have started the journey e.g. the role of climate assemblies… what next? 12. Decision making under deep (climate) uncertainty by the financial sector We acknowledge the funding of the manuscripts published in this Research Topic by the Clean Air Task Force. We hereby state publicly that the Clean Air Task Force has had no editorial input in articles included in this Research Topic, thus ensuring that all aspects of this Research Topic are evaluated objectively, unbiased by any specific policy or opinion of the Clean Air Task Force.

Today, Boston is in a uniquely powerful position to make our city more affordable, equitable, connected, and resilient. We will seize this moment to guide our growth to support our dynamic economy, connect more residents to opportunity, create vibrant neighborhoods, and continue our legacy as a thriving waterfront city.Mayor Martin J. Walsh's Imagine Boston 2030 is the first citywide plan in more than 50 years. This vision was shaped by more than 15,000 Boston voices.

In Transforming California, Stephanie Pincetl argues that the transformation of nature in order to enhance economic development lies at the heart of much of the state's recent history. She sees late-twentieth-century California on a path of continued environmental degradation, gripped by cynicism about government. Transforming California describes the evolution of the state's institutions of government as they apply to land use and development, and it shows how land-use decisions affect people's quality of life and their daily interactions with each other and with their environment. Pincetl offers an alternative vision for the renewal of the democratic spirit and process in California and for a reconciliation with nature.

Cities have experienced an unprecedented rate of growth in the last decade. More than half the world's population lives in urban areas, with the U.S. percentage at 80 percent. Cities have captured more than 80 percent of the globe's economic activity and offered social mobility and economic prosperity to millions by clustering creative, innovative, and educated individuals and organizations. Clustering populations, however, can compound both positive and negative conditions, with many modern urban areas experiencing growing inequality, debility, and environmental degradation. The spread and continued growth of urban areas presents a number of concerns for a sustainable future, particularly if cities cannot adequately address the rise of poverty, hunger, resource consumption, and biodiversity loss in their borders. Intended as a comparative illustration of the types of urban sustainability pathways and subsequent lessons learned existing in urban areas, this study examines specific examples that cut across geographies and scales and that feature a range of urban sustainability challenges and opportunities for collaborative learning across metropolitan regions. It focuses on nine cities across the United States and Canada (Los Angeles, CA, New York City, NY, Philadelphia, PA, Pittsburgh, PA, Grand Rapids, MI, Flint, MI, Cedar Rapids, IA, Chattanooga, TN, and Vancouver, Canada), chosen to represent a variety of metropolitan regions, with consideration given to city size, proximity to coastal and other waterways, susceptibility to hazards, primary industry, and several other factors.

"Net zero energy buildings, equilibrium buildings or carbon neutral cities – depending on location and the reasons for making the calculation, the numbers are run differently. The variety of terms in use indicates that a scientific method is still lacking – which is a problem not just in regard to international communication, but also with respect to planning processes as a response to energy challenges. The clarification and meaning of the most important terms in use is extremely important for their implementation. Since October 2008, a panel of experts from an international energy agency has concerned itself with these topics as part of a project entitled “Towards Net Zero Energy Solar Buildings”. The objective is to analyse exemplary buildings that are near a zero-energy balance in order to develop methods and tools for the planning, design and operation of such buildings. The results are documented in this publication: In addition to the presentation of selected projects, it is not just architectural showcase projects that are shown – the focus is on relaying knowledge and experience gained by planners and builders. Even if many questions remain unanswered: Project examples that have already been implemented prove on a practical basis that the objective of a zero energy balance is already possible today."

The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for assessing the science related to climate change. It provides policymakers with regular assessments of the scientific basis of human-induced climate change, its impacts and future risks, and options for adaptation and mitigation. This IPCC Special Report on the Ocean and Cryosphere in a Changing Climate is the most comprehensive and up-to-date assessment of the observed and projected changes to the ocean and cryosphere and their associated impacts and risks, with a focus on resilience, risk management response options, and adaptation measures, considering both their potential and limitations. It brings together knowledge on physical and biogeochemical changes, the interplay with ecosystem changes, and the implications for human communities. It serves policymakers, decision makers, stakeholders, and all interested parties with unbiased, up-to-date, policy-relevant information. This title is also available as Open Access on Cambridge Core.