(a) Global CO2 emissions from fossil-fuel combustion, cement manufacture, and gas flaring and global population, 1800 – 2014 (sources: carbon emissions data from cdiac.ornl.gov, with years 2012 – 2014 based on data from BP statistical review; population data from www.census.gov). (a) Global CO2 emissions from fossil-fuel combustion, cement manufacture, and gas flaring and global population, 1800 – 2014 (sources: carbon emissions data from cdiac.ornl.gov, with years 2012 – 2014 based on data from BP statistical review; population data from www.census.gov). CO2 emissions are expressed in millions of metric tonnes of carbon; to convert to the mass of CO2 multiply by the molecular ratio 3.667. (b) Mean annual CO2 concentration in the atmosphere from two sources: the Law Dome ice-core dataset (Etheridge et al. 1996; MacFarling Meure et al. 2006); and the Mauna Loa Observatory measurements from the Earth System Research Laboratory (source: www.esrl.noaa.gov/gmd/ccgg/trends/data.html). Philip S. Ringrose Petroleum Geoscience 2017;23:287-297 © 2017 The Author(s)‏