Kaya Identity Defines Realistic Negative Emissions Targets for Large Nations and the World

Abstract Our primary goal in this paper is to outline a methodology for developing realistic energy transition scenarios using existing and cost-effective technologies including negative emissions technologies. We discuss data sources, build projections of GDP, consumption of various energy resources, and energy transition costs. We discuss in detail the scenario for the USA, and briefly for China and India. We also review worldwide energy transition scenarios, and we address the question of what the expected CO2 emissions under a "business as usual" scenario, how much negative emissions would be required to achieve net zero, and what should be the rate of decarbonization of the energy system to stay within carbon budget associated with dT < 2°C. Energy systems have tremendous scale and inertia. Trends of systems development play out over several decades and in many cases growth rate of the emissions intensity of the energy system, or energy intensity of the economy can be confidently extrapolated assuming exponential growth or decline trends. This exponential approximation leads to a very simple yet beautiful result: Compound Annual Growth Rate CAGR of CO2 emissions = CAGR of Emissions intensity of the Energy System + CAGR of Energy Intensity of Economic Output + CAGR of Economic output per capita + CAGR of Population projection. Our secondary aim is education. We are applying this methodology to teach student engineers at Texas A&M University, as well as practicing engineers, about negative emissions targets and realistic transition strategies. We discuss how much energy per capita is necessary for sustaining our modern civilization and the linkage between energy use and economic growth.