Long description

This figure consists of a pair of very similar line charts showing global carbon dioxide emissions, methane emissions and total greenhouse gas emissions. Chart (a) on the left is labelled ‘IPCC emissions projections to keep global temperature rise below 1.5 degrees Celsius’. Chart (b) on the right is labelled ‘IPCC emissions projections to keep global temperature rise below 2 degrees Celsius’. Both charts have x-axes which run from 1995 to 2100, with the years from 2000 through to 2100 marked in 20-year intervals. They both have y-axes labelled ‘gigatonnes of CO2 equivalent per year’, with a scale running from minus 20 to plus 60 gigatonnes labelled from zero to 60 in 20-gigatonne steps. Zero is also labelled ‘net zero’. A label just to the right of the y-axis shows that emissions between 1995 and 2015 are ‘historical’. In the 1.5 degree chart, the total historical greenhouse gas emissions, labelled GHGs, are shown as a black line rising very unevenly from about 40 gigatonnes in 1995 up to about 55 gigatonnes in 2015. A short solid blue line continues rising to about 56 gigatonnes in 2020. From this point a dotted blue line extends onwards, rising slightly to about 59 gigatonnes in 2045 and then falling slightly back to 55 gigatonnes by 2100. This dotted line is labelled ‘policies in place in 2020’. From the 2020 point the solid blue line continues, falling to about 40 gigatonnes in 2030, 20 gigatonnes in 2040, about 10 gigatonnes in 2060, zero in 2080 and about minus 2 gigatonnes in 2100. A label to the right of the line says ‘GHGs reach net zero later than CO2’. The historical CO2 emissions are shown by a solid black line starting at about 28 gigatonnes in 1995 and rising unevenly to almost 40 gigatonnes in 2015. From this point, the solid purple line continues on at the same level until 2020. A dotted purple line, indicating ‘policies in place in 2020’, then continues almost horizontally. This rises slowly to about 42 gigatonnes in 2040 and remains at that level until 2100. From the 2020 point, a solid purple line falls rapidly down to 6 gigatonnes in 2040 and reaches zero just after 2050. This point is indicated by a vertical black double-headed arrow reaching down to the x-axis and labelled ‘Net zero CO2 around 2050’. The purple line continues falling to about minus 8 gigatonnes in 2100. The historical methane emissions, labelled CH4, are shown by a solid black line starting at about 8 gigatonnes in 1995 and rising to 10 gigatonnes in 2015. This line continues in brown at the same level on to 2020. From this point, a dotted brown line continues on almost horizontally on to 2100. From the 2020 point, the solid brown line falls slowly to about 6 gigatonnes in 2060 and continues at the same level on to 2100. In the 2 degree chart, the total historical greenhouse gas emissions, labelled GHGs, are shown as a black line rising very unevenly from about 40 gigatonnes in 1995 up to about 55 gigatonnes in 2015. A short solid blue line continues rising to about 56 gigatonnes in 2020. From this point, a dotted blue line extends onwards, rising slightly to about 59 gigatonnes in 2045 and then falling slightly back to 55 gigatonnes by 2100. This dotted line is labelled ‘policies in place in 2020’. From the 2020 point the solid blue line continues, falling to about 45 gigatonnes in 2030, 28 gigatonnes in 2040, about 10 gigatonnes in 2060 and 6 gigatonnes in 2100. A label to the right of the line says ‘GHGs reach net zero later than CO2’. The historical CO2 emissions are shown by a solid black line starting at about 28 gigatonnes in 1995 and rising unevenly to almost 40 gigatonnes in 2015. From this point, a solid purple line continues on at the same level until 2020. A dotted purple line, indicating ‘policies in place in 2020’, then continues almost horizontally. This rises slowly to about 42 gigatonnes in 2040 and remains at that level until 2100. From the 2020 point, the solid purple line falls rapidly down to 20 gigatonnes in 2040 and reaches zero in 2070. This point is indicated by a vertical black double-headed arrow reaching down to the x-axis and labelled ‘Net zero CO2 2070’. The purple line continues falling to about minus 3 gigatonnes in 2100. The historical methane emissions, labelled CH4, are shown by a solid black line starting at about 8 gigatonnes in 1995 and rising to 10 gigatonnes in 2015. This line continues in brown at the same level on to 2020. From this point, a dotted brown line continues on almost horizontally on to 2100. From the 2020 point, the solid brown line falls slowly to about 6 gigatonnes in 2060 and continues at the same level on to 2100.