Costof Emissions Calculator

Putting a dollar figure on a tonne of carbon dioxide rests on the economics of externalities: the damage from combustion falls on people who never bought the fuel, so the market price understates the true cost. This calculator separates that gap into three additive components, each expressed as dollars per tonne so they can be summed and then multiplied by annual emissions. The social cost of carbon captures global, long-horizon climate damages such as crop losses, sea level rise, and heat mortality, and is dominated by the discount rate chosen. The US Interagency Working Group used about 51 dollars per tonne of CO2 for 2020 emissions at a 3 percent discount rate, while the EPA 2023 revision, built on a 2 percent Ramsey rate, published central values near 190 dollars. Health damage costs are separate and local, arising from co-pollutants such as fine particulate matter and nitrogen oxides released alongside CO2; the WHO attributes roughly 4.2 million premature deaths a year to ambient air pollution. Regulatory penalty rates capture direct legal liability, such as the 100 euro per tonne excess emissions penalty under the EU Emissions Trading System. The main caveat is double counting: the social cost of carbon already embeds some health damages, so entering both at full value inflates the total.

The intellectual foundation was laid by Arthur Pigou, whose 1920 book The Economics of Welfare argued that activities imposing uncompensated costs on others should face a corrective tax equal to the marginal external damage. Translating that principle into a number for carbon took another seventy years. William Nordhaus of Yale built the DICE integrated assessment model in the late 1980s and early 1990s, coupling a simple climate model to an economic growth model so a marginal tonne of emissions could be traced to discounted global consumption losses; he shared the 2018 Nobel Memorial Prize in Economic Sciences for this work. Competing models including PAGE, developed by Chris Hope at Cambridge, and FUND, by Richard Tol, produced estimates that varied widely, mainly because of discount rate assumptions. Regulatory practice followed. In 2010 a US Interagency Working Group published the first official social cost of carbon estimates for federal rulemaking, initially around 21 dollars per tonne, revised upward in later rounds. The 2006 Stern Review, commissioned by the UK Treasury, produced far higher damage estimates by using a near-zero pure rate of time preference, sparking a long methodological debate with Nordhaus. Separately, the EU Emissions Trading System, launched in 2005, created explicit statutory penalties for uncovered emissions, and the National Academies of Sciences issued recommendations in 2017 for modernizing the estimation framework.