The Scientific Advisory Group of the World Meteorological Organization's (WMO) Global Atmosphere Watch (GAW), with includes currently 3 scientists from ICOS, reports yearly in Greenhouse Gas Bulletin the latest trends and atmospheric burdens of the most influential, long-lived greenhouse gases; carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), as well as a summary of the contributions of the lesser gases. The Greenhouse Gas abundances are calculated from the global in situ network of the WMO GAW programme, to which also ICOS atmospheric stations contribute.
This year's bulletin focuses on historic CO2 records from ice-cores and the record increase in CO2 from 2015 to 2016 of 3.3 ppm to 403.3 ppm. The increase of CO2 in the last 150 years is a factor of 100 higher than any period since the last ice age ended 23 000 years ago. During the ice ages in the last 800 000 years, CO2 never reached 280 ppm and in cold periods was as low as 180 ppm. To see 400 ppm of CO2 on Earth we have to go back 3-5 million years in the Pliocene when the equilibrium climate was 2-3 degrees Celcius warmer than today and sea level was 10-20m higher. Ocean heat storage will make that we have some time left before the equilibrium climate corresponding to current greenhouse gas levels will be reached, but unless we succeed in removing CO2 from the atmosphere, most of CO2 added in the last 150 years will remain in the atmosphere for centuries to come.
The bulletin ends with:
"The longer we wait to implement the Paris Agreement, the greater the commitment and the more drastic (and expensive) the required future emission reductions will need to be to keep climate change within critical limits."
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