The Road to Carbon Neutrality - Ten New Insights in Climate Science

In 2021, the global community hit some grim milestones when it comes to climate change. The April 2021 report Ten New Insights in Climate Science, published by Future Earth, the Earth League, and the World Climate Research Programme (WCRP), cites trends in growth of methane and nitrous oxide emissions that could increase warming by 2.7 degrees Celsius, an increase in megafires across the world, and the high risk of climate tipping events occurring (e.g., the loss of ice sheets in Greenland, the degradation of the Amazon rainforest, and the weakening of Atlantic Ocean circulation).

But the report also retains hope. For example, it shows that it’s still possible to stabilize global warming at 1.5 degrees Celsius and that building resilience through conservation and management is achievable. Another insight from the report that is particularly relevant to the sustainability education and consulting community is the need to support household behavior change on climate change mitigation efforts. This can be achieved through working with local cities and municipalities to support individual behavior change by simply making it easier for people make environmentally beneficial choices, which can be implemented through local Climate Action Plans (CAPs).

A Climate Action Plan (CAP) is a community-benefits-based approach that incorporates climate change mitigation and adaptation measures into local planning priorities. Essentially, we help take a global issue to the local level by assisting the local governments in developing strategies that can help reduce a city’s carbon footprint.

CAPs also help communities assess their contributions in reducing climate change impacts. A couple of metrics can help make these numbers relatable to citizens: the social and mortality costs of carbon.

The social cost of carbon is a metric that is increasingly used by the United States and other countries around the world to put an economic measurement on carbon output. The metric is an estimate, in dollars, of the economic damages (e.g., human health, agriculture, energy usage, coastal flooding) that result from each additional ton of greenhouse gas emissions produced. Typically, short and long-term benefits outweigh the cost of a project, such as a highway improvement project that increases automobile capacity. However, when the social cost of carbon is added into the equation, the long-term costs attributed to the increased carbon emissions by the cars using that highway may outweigh the benefits that the highway would provide by decreasing car trips by a few minutes.

Recently, the mortality cost of carbon has also been integrated into this cost-benefit metric. This metric shows the stakes in even starker contrast by highlighting the cost of human lives from carbon emissions. A July 2021 paper published in Nature Communications found that every 4,434 metric tons of carbon dioxide added to the atmosphere in 2020 would cause one excess death globally between 2020–2100. Thus, for a typical American town of 40,000 people where 2020 emissions were equivalent to about 646,000 metric tons of carbon dioxide, the mortality cost of carbon from 2020 emissions would result in nearly 146 excess deaths globally by 2100. In contrast, though, this metric also shows the potential positive impact for global climate change through the number of lives saved if all 40,000 residents are committed to reducing their carbon footprint.

Although still a new concept, the mortality cost of carbon metric can show how a city working to reduce greenhouse gas emissions will help stem the tide of climate change and make changes that positively impact the local community they serve. This measurement also accounts for the long-term benefits of increasing equity, buildings and energy, transportation, land use, consumption, and waste reduction. The added benefit is that a city’s climate commitment takes a more systemic approach, rather than relying on individuals to change their particular habits.

For example, if a city builds commercial business and housing development around the city center, community members take fewer car trips when goods and services are centralized. This facilitates behavior change on an individual level. It’s also possible to translate the social cost of carbon into certain goals to identify both how to achieve those goals and the ultimate benefit of those that can be applied to any specific project or policy.

Though this is a new concept that has yet to take hold in cities in the U.S., the scientific community is well prepared to help communities consider this measurement in their climate planning efforts. Metrics like the social and mortality costs of carbon hold a great deal of potential from local governments to mitigate the impact of climate change both globally and for their communities.