In his recent post Euan Mearns projected global energy requirements out to 2100. In this brief post I apply Euan’s methodology to carbon dioxide emissions, which are closely correlated with energy consumption. The projections show CO2 emissions peaking around 2075 under the UN low population growth scenario but continuing to increase through 2100 under the UN’s medium and high population growth scenarios. The alleged “dangerous interference” threshold of 1 trillion tons of cumulative carbon emissions (3.67 trillion tons of CO2) targeted by the Paris Climate Agreement is exceeded between 2050 and 2055 under all three scenarios.
Figure 1 plots global CO2 emissions and total primary energy consumption between 1965 and 2016. The data are from the BP 2016 Statistical Review. Note that the CO2 data cover only emissions from fossil fuel combustion. Other greenhouse gases such as methane and Nox are not included:
Figure 1: Global CO2 emissions and primary energy consumption, 1965-2016
The near-exact match between CO2 emissions and energy consumption (R2 = 0.998) is obvious. What is not obvious is any detectable impact from the world’s efforts to cut CO2 emissions, which began at Kyoto over 20 years ago in 1997. (The combination of flattening emissions and moderate economic growth after 2013 has been claimed as evidence that energy and emissions are finally becoming decoupled, but global CO2 emissions in 2017 have risen again – by about 2% over 2016 according to Carbon Brief.)
Figure 2 plots global per-capita CO2 emissions since 1965, calculated from the BP emissions data and the UN’s global population estimates:
Figure 2: Global per-capita CO2 emissions
This plot is similar to the plot of per-capita energy consumption shown in Figure 1 of Euan Mearn’s post, which we would expect given the close correlation between emissions and energy, but the trend is less steep. The likely reason is that the proportion of world primary energy supplied by low-carbon sources (nuclear, hydro, renewables) has increased from about 6% in 1965 to approaching 15% now. Nevertheless the overall trend is still upward.
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