Carbon Calculus™: New metrics for sustainable decision making

<title>Abstract</title> <p> Driven by the greenhouse effect, emitted GHGs cause an energy imbalance represented by radiative forcing and realized through increasing global average temperature. Between calendar years 1990 and 2023, 81% of the increase in atmospheric radiative forcing was caused by carbon dioxide (CO ₂ ) emissions alone. Presented with multiple possible decarbonization projects and constrained by available budgets, organizations face a difficult decision-making process to decide which actions to take, when, and in what order to optimize their CO ₂ reduction pathway. Existing microeconomic metrics like time-value of money, net present value, and breakeven are useful to compare the monetary value of alternative scenarios. However, since these decisions are largely motivated by decarbonization, what comparable carbon-specific metrics can be used? Without quantitative clarity beyond economics, organizations lack confidence in decarbonization decisions, leading to delayed, under-informed, and suboptimal capital allocation. Derived from carbon-climate impulse response models, Carbon Calculus™ is a novel decarbonization decision-making tool that integrates the time value of CO ₂ into a simple CO ₂ sink dissipation model. New metrics are defined, including Net Present Value of CO ₂ (NPV _CO2 ), which quantitatively values and compares decarbonization strategies across different magnitudes and time frames. Results quantify the opportunity cost of decarbonization and quantitatively support the importance of early decarbonization action. If storage is not permanent, more CO ₂ must be captured to offset its temporality. One ton of CO ₂ removed &amp; permanently stored today has an equivalent cumulative impact reduction to 75.7 tons CO ₂ removed &amp; temporarily stored for 1 year. Furthermore, decarbonization actions become less valuable the longer we wait to act. Delaying a decarbonization action by 10 years will require a 14.2% increase in reductions 10 years from now to neutralize the lost opportunity cost imposed by delaying. The intention behind Net Zero targets is to reduce the total quantity of emissions for reductions in atmospheric temperature. With Carbon Calculus, sustainability goals can be updated to not just reach Net Zero by a specific date, but also minimize the cumulative CO ₂ emitted along the way. </p>