Quantifying Global Greenhouse Gas Emissions in Human Deaths to Guide Energy Policy

The paper begins by highlighting the continued increase in global greenhouse gas emissions despite warnings from the scientific community. It emphasizes the reluctance to implement strong energy policies due to political and psychological factors. The introduction then establishes a direct link between climate change and human mortality, detailing various direct (heat waves), intermediate (crop failures, droughts, floods), and indirect (conflict, displacement) causes of death related to climate change. The authors argue that human deaths, being the most significant consequence of climate change and universally understood, should be the primary metric for quantifying future harms caused by carbon emissions. They choose to focus on human deaths rather than broader measures like disability-adjusted life years (DALYs) due to the inherent complexities and debatable assumptions associated with DALYs. The introduction sets the stage for a review of methods to quantify carbon emissions in terms of human deaths and to derive energy policy recommendations based on those quantifications.

The paper reviews existing literature on quantifying climate change-related deaths. It introduces the "1000-ton rule", which posits that burning 1000 tons of fossil carbon leads to one premature death. This rule is supported by independent studies from different fields, such as philosophy and economics. One study by philosopher John Nolt linked the average American's carbon emissions to the death or suffering of one or two future individuals. Economist Robert Bressler estimated that for every 4434 metric tons of CO2 emitted beyond 2020 levels, one person globally would die prematurely from extreme heat. Xu et al.'s research on temperature niches suggests that each degree of warming above the baseline leaves approximately 1 billion humans outside their temperature niche, implying high mortality if migration is impossible. The review concludes that even small increases in warming lead to significant increases in mortality, underscoring the importance of every effort to reduce emissions.

The paper's methodology relies primarily on a synthesis of existing literature and established data points regarding carbon emissions and climate change impacts. It focuses on consolidating findings from various studies to establish a quantitative link between carbon emissions and human mortality. The central approach is to use the "1000-ton rule" as a rule of thumb to convert carbon footprints into an approximate number of human lives lost. This involves analyzing data on total carbon emissions, carbon budgets for specific warming levels, projected population growth, and estimates of mortality from different climate-related causes. The authors use this approach to illustrate its application at various scales, from individual actions (e.g., air travel) to large-scale energy projects (e.g., the Adani Carmichael coal mine). The methodology also involves analyzing the implications for corporate accountability, exploring the possibility of applying concepts like "corporate death penalties" and asset forfeiture laws to hold corporations responsible for their carbon emissions and related deaths. The authors further discuss the use of these quantitative estimations to inform energy policy at both national and international levels.

The core finding is the establishment and support for the "1000-ton rule," which estimates a one-to-one correspondence between the burning of 1000 tons of fossil carbon and a premature death. The authors also highlight the disproportionate impact of climate change on poorer populations, suggesting that if global warming reaches 2°C, primarily wealthier nations will be responsible for the deaths of approximately 1 billion individuals, largely from poorer nations. This finding strongly supports the necessity of immediate and significant reductions in carbon emissions. The paper also finds convergence between multiple independent studies in supporting the order of magnitude estimate provided by the 1000-ton rule. This convergence strengthens the argument for the rule's use as a practical tool for assessing the human cost of carbon emissions. The analysis extends beyond individual actions and explores the implications for corporations and industries, suggesting criteria for industry-wide penalties and the potential use of asset forfeiture laws to address carbon-related deaths. The authors quantify the human cost of coal-fired power plants, and by extension fossil fuels in general, noting that the number of deaths caused often exceeds the number of people employed in the industry. Specific examples are provided in the paper, such as the Adani Carmichael coal mine and the US coal industry, to illustrate the significant number of deaths linked to these sources.

The discussion section addresses the challenges of causation and attribution in linking specific carbon emissions to individual deaths. The authors argue that the 1000-ton rule provides a proportional approach to assigning responsibility, making the consequences of carbon emissions more easily understood. The authors assert that even without explicit intent to kill, the fossil fuel industry's knowledge of potential harm and their continued actions constitute manslaughter. The discussion further explores the ethical and moral implications of the high death tolls attributed to carbon emissions, highlighting the need for urgent action. The paper emphasizes that the "1000-ton rule" is an approximation, and the real number of deaths is likely to vary significantly due to several factors including population trends, age, and geographic location. The findings underscore the severity of the situation and argue for a shift from gradual decarbonization to much more aggressive energy policies to safeguard human lives. This includes banning certain practices, prioritizing specific policy measures, and exploring mechanisms for economic liability and asset forfeiture.

The paper concludes that the 1000-ton rule provides a valuable tool for understanding and communicating the human cost of carbon emissions. The findings underscore the urgent need for aggressive energy policies to minimize future deaths from climate change. Recommendations include a rapid transition to renewable energy, substantial improvements in energy efficiency, and addressing corporate accountability for carbon emissions. Further research should focus on refining the accuracy of death toll predictions and developing detailed strategies for implementing these policies effectively.

The study's primary limitation is the inherent uncertainty and approximation involved in estimating future death tolls from climate change. The 1000-ton rule provides an order-of-magnitude estimate, acknowledging potential variability in death rates across different regions, age groups, and specific causes of death. The complex causal chain between carbon emissions and mortality presents challenges in accurate attribution. Furthermore, the study acknowledges the difficulty in predicting population trends and the influence of factors such as technological advancements and societal adaptations on future mortality rates. The paper itself focuses primarily on human deaths, neglecting other important aspects of the climate crisis's impact on human well-being.