How are atmospheric concentrations of greenhouse gases developing compared with levels consistent with limiting the increase in global mean temperature to 2 °C or even 1.5 °C above pre-industrial levels?

Policy Question
Indicator codes: CSI 013 , CLIM 052

Key messages

(21 Jan 2019)

  • The annual average concentration of CO2, the most significant anthropogenic greenhouse gas, increased to 403 and 405 parts per million (ppm) in 2016 and 2017, respectively.
  • The total concentration of all greenhouse gases, including cooling aerosols, reached a value of 449 ppm in CO2 equivalents in 2016 — an increase of more than 4 ppm compared with 2015, and 33 ppm more than 10 years ago. 
  • If the concentrations of the different greenhouse gases continue to increase at current rates, the peak concentration levels required to stay below a temperature increase of 1.5 °C  above pre-industrial levels, could be reached within the next 5-16 years. Peak concentration required to stay below a maximum 2 °C temperature increase could be reached in 17-40 years. 
  • Given the increasing concentration levels, negative emissions may become important to increase the probability of remaining below the Paris temperature objectives.

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