The latest analysis of observations from the WMO GAW Programme shows that globally averaged surface mole fractions calculated from this in-situ network for carbon dioxide , methane and nitrous oxide reached new highs in 2018, with CO2 at 407.8±0.1 ppm, CH4 at 1869±2 ppb and N2O at 331.1±0.1 ppb. These values represent, respectively, 147%, 259% and 123% of pre-industrial (before 1750) levels. The increase in CO2 from 2017 to 2018 was very close to that observed from 2016 to 2017, and practically equal to the average yearly increase over the last decade. For CH4, the increase from 2017 to 2018 was higher than both that observed from 2016 to 2017 and the average over the last decade. For N2O, the increase from 2017 to 2018 was also higher than that observed from 2016 to 2017 and the average growth rate over the past 10 years. The National Oceanic and Atmospheric Administration (NOAA) Annual Greenhouse Gas Index (AGGI) shows that from 1990 to 2018 radiative forcing by long-lived greenhouse gases (LLGHGs) increased by 43%, with CO2 accounting for about 81% of this increase.
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