Every ton of carbon dioxide people emit comes at a price – not just in terms of the financial consequences of damage from floods, heat waves and droughts, but also in terms of the cost of human life. According to a new study that calculated this “death cost of carbon,” a significant reduction in emissions today could prevent tens of millions of premature deaths over the 21st century.
The research published Thursday in Nature communication, breaks out part of the Social Cost of Carbon (SCC), a metric that calculates the future damage from today’s carbon emissions, in order to price those emissions. The SCC helps governments weigh the costs and benefits of climate regulations, climate protection projects and fossil fuel infrastructure. The Biden administration is currently in the process of revising the U.S. federal government’s estimate of this metric to incorporate the latest science on climate impact, as recommended in a 2017 report by the National Academies of Sciences, Engineering and Medicine. These effects include expected premature deaths. The Biden administration temporarily set its SCC estimate to around $ 51 per ton, close to what it was in the Obama years – before the Trump administration cut it down to just $ 1 per ton.
R. Daniel Bressler, a Ph.D. Columbia University candidate and author of the new study, was interested in how SCC estimates would change if researchers included the latest scientific evidence on temperature-related deaths related to climate change. He also broke this component out separately so that the human figure could be more clearly understood. To do this, Bressler updated a model by the economist William Nordhaus (who received the Nobel Prize in Economics for this model in 2018). It effectively links different climate scenarios with their economic impacts to calculate the social costs of carbon and determine the optimal plan to reduce emissions. Bressler wanted to optimize the model in order to make climate-related mortality a larger contribution to the total costs of climate change and to incorporate extensive recent research on this topic. “There has really been an explosion in literature [on the topic] in the past ten years, ”he says.
When Bressler incorporated this newer research, he calculated that – in a scenario where emissions continued to rise – every 4,434 metric tons of carbon dioxide added to the atmosphere in 2020 would result in an additional death by 2100 worldwide. (By comparison, 3.5 Americans emit that much in their lifetime.) Generally speaking, one million tons of CO2 that will be emitted in 2020 – or what 35 commercial planes, 216,000 automobiles, or 115,000 American households will shed in a year – would cause 226 premature deaths by the end of the century.
Taking these deaths into account increased the social cost of CO2 from $ 37 to $ 258 per tonne, making it more economically effective to cut emissions now. It also makes rapid emissions reductions and full decarbonization by 2050 more cost-effective compared to the more conical approach that Nordhaus’ model originally recommended. The result is “a pretty big difference in relation to the proposed climate policy,” says Bressler. A faster emissions reduction path, rather than allowing emissions to continue to rise unabated, would reduce premature deaths from around 83 million to nine million by 2100.
Bressler notes that his study has a large area of uncertainty and that the mortality numbers only include deaths related to temperature. Ideally, disease transmissions, flooding and other climate-related impacts should also be considered, but these elements are less explored. Bressler’s work is similar to that of other scientists, including that of the Climate Impact Lab collaboration, to review the social costs of carbon, says Maureen Cropper, University of Maryland economist and co-chair of the group that authored the National Academies 2017 review report. Bressler’s estimate of the SCC is much higher than that of the Climate Impact Lab because of various economic assumptions he’s made, but it’s valuable to translate this aspect of the social cost of carbon into more abstract dollar numbers, Cropper adds. “When you express things in relation to people,” she says, “I think it resonates.”