FIGURE 14.34 The emissions of CO2 during the first quarter of 2012 fell to the lowest levels since 1992. Carbon dioxide emissions during this period fell to their lowest levels since 1986, which was largely the result of substituting natural gas for coal for electrical generation. (From U.S. EIA, http://www.eia.gov/todayinenergy/ detail.cfm?id$=7350#tabs_co2emissions-1)