# solution

In this problem, we are going to analyze the existing proven reserves for coal, oil and natural gas in terms of how much longer we can expect supplies to last and the greenhouse gas impact of consuming those supplies. Estimates for the amount of fossil fuels that are recoverable with known technology are highly uncertain. However, estimates are available that give rough figures that can help guide society’s long-term energy decisions. The table below provides estimates of the proven reserves and current consumption for fossil resources that come from BP’s Statistical Review of World Energy. Fossil Resource Reserves Annual Consumption Years left at current consumption Emission factor Carbon emission embodied in reserves (billion metric tons CO2) Coal 1,139 billion 5.22 billion metric tons metric tons Petroleum 1,707 billion barrels 35.2 billion barrels Natural Gas 6,589 trillion cubic feet 125.1 trillion cubic feet
(a) Estimate the number of years remaining for human fossil fuel consumption for each resource assuming a constant rate of consumption. (3 pts) (b) At current growth rates natural gas annual consumption will double in approximately 30 years and petroleum annual consumption will double in 60 years. The coal consumption rate is currently declining slightly since 2013. Based on this information, how urgently should we seek alternatives to these dominant energy sources for the purpose of energy supply? Explain your reasoning. (3 pts) (c) Next, we are going to calculate the carbon dioxide emissions that would occur if all the proven reserves of each resource is fully consumed. Using the emission factors available from the EPA Greenhouse gas equivalencies calculator, calculate the total carbon dioxide emissions that would be emitted if all the reserves of each resource were consumed. (6 pts) (d) In order to keep climate change from exceeding 2 degrees Celsius, scientists estimate that humans can only emit an additional 1,200 billion tons of CO2 from fossil sources. Based on your calculations, is it more urgent to reduce fossil fuel consumption for climate purposes or energy supply purposes?