Carbon cost is the total economic damage caused by releasing one ton of carbon dioxide into the atmosphere. It puts a dollar figure on the real-world harm of climate change, including crop losses, health problems, property damage from flooding, and rising energy bills. The most widely used version of this concept, called the social cost of carbon, is a central tool in government policy and increasingly in corporate decision-making.
How the Social Cost of Carbon Works
The social cost of carbon (SCC) estimates, in dollars, the long-term damage done by emitting one ton of CO2 in a given year. It’s meant to be comprehensive: it accounts for changes in agricultural productivity, human health effects, property damage from increased flood risk, and shifts in energy costs like higher air conditioning bills and lower heating bills. When a government agency proposes a new regulation, the SCC helps weigh whether the climate benefits of that rule justify its costs.
One important feature of the SCC is that it rises over time. Future emissions are expected to cause larger damages because physical and economic systems become more stressed as the climate changes. A ton of CO2 emitted in 2040 is projected to cause more harm than a ton emitted today, partly because global GDP keeps growing and many damage categories scale with economic output.
What Gets Counted in the Calculation
The damages folded into carbon cost estimates are broader than most people realize. Food production alone generates roughly $8.3 trillion in health-related costs and $5.7 trillion in ecosystem damage globally each year. These are what economists call externalities: real costs that don’t show up in the price you pay at the grocery store or the gas pump. In high-income countries, the hidden environmental and health costs embedded in food run about $2.52 per 1,000 calories consumed, roughly double the $1.02 per 1,000 calories in low-income countries.
Meat production is a major driver, accounting for 51% of the worldwide total of food-related externalities. In high-income countries, animal-sourced foods are responsible for 84% of the total. Research published in Nature found that shifting diets away from animal products could save up to $7.3 trillion in health and ecosystem costs while cutting carbon emissions.
The Discount Rate Problem
One of the most contentious parts of calculating carbon cost is the discount rate: how much less you value future damages compared to damages happening right now. A higher discount rate means future climate harms count for less in today’s dollars, which lowers the estimated cost per ton. A lower rate treats future generations’ losses as nearly as important as present ones, which raises the number significantly.
For years, U.S. agencies used default discount rates of 3% and 7% based on guidance from the Office of Management and Budget issued in 2003. In 2023, OMB revised that guidance and recommended a 2% rate for evaluating long-term effects. That single change pushes the social cost of carbon substantially higher, because damages projected for 2060 or 2080 retain more of their value in present-day terms.
What the Numbers Actually Look Like
The price tag per ton of CO2 varies enormously depending on who’s calculating it and what assumptions they use. At the policy level, the Intergovernmental Panel on Climate Change has estimated that meeting the goals of the Paris Agreement would require a carbon price of $135 to $5,500 per metric ton by 2030, and $245 to $13,000 per metric ton by 2050. That enormous range reflects deep uncertainty about how sensitive the climate is, how fast economies will grow, and how effectively societies will adapt.
Those figures represent what carbon would need to cost to actually change behavior at the scale required. Current real-world carbon prices, where they exist, fall far below that range.
How Companies Use Carbon Cost Internally
A growing number of corporations set their own internal carbon price to guide investment decisions, even when no government requires them to. Two main approaches dominate. A carbon charge works like a self-imposed tax: a company charges its own business units a fee for every ton they emit, creating a financial incentive to reduce emissions. A shadow price doesn’t move real money around but instead factors a hypothetical cost of carbon into decisions about new projects, equipment purchases, or supply chain changes.
The prices companies choose vary widely. Yale University uses $40 per ton for its internal carbon charge. Microsoft has used a price between $4 and $5 per ton, calculated by dividing the cost of its environmental initiatives by its total emissions. Société Générale, the French bank, set its internal carbon tax at about $10.80 per ton. Some companies, like Delta and Qantas airlines, use internal pricing but don’t disclose the specific numbers.
Companies typically set their internal price using one of two strategies: adopting a country-specific estimate of the social cost of carbon, or developing a firm-specific price that reflects their own emissions reduction targets and revenue goals.
Carbon Cost Across a Product’s Life
When carbon cost is applied to a specific product rather than to the economy as a whole, it typically follows a life cycle assessment. This traces the carbon footprint from raw material extraction through manufacturing, transportation, use, and disposal. Each stage gets assigned emission values: the fuel burned during harvesting, the energy consumed in a factory, the diesel used by shipping trucks, and even the methane released when the product ends up in a landfill.
Life cycle assessments can also include indirect emissions that aren’t immediately obvious. The concrete in a building, for example, carries embedded emissions not just from mixing cement but from the lime production that made the cement possible. Coal-fired electricity carries emissions from the mining process on top of what comes out of the power plant smokestack. These layered calculations are what make a full carbon cost so much higher than the emissions from any single step in isolation.