Nevertheless, they persist! GHGs in the atmosphere

Once emitted, anthropogenic GHGs do not dissipate like steam from a pot on a stovetop. They persist. Some for much longer than others. Again, because of the complexity of the ecosystem, scientists continue to refine their predictions about GHG persistence. Carbon dioxide’s heat-trapping ability and persistence in the atmosphere is the most complex. That is because, how long CO2 remains in the atmosphere is determined not only by chemical breakdowns (as it is with the other GHGs) but also with the absorptive capacity of the oceans, soil, and plant life in the carbon cycle. Much of the anthropogenic CO2 takes 50-100 years to be reabsorbed through the carbon cycle. That’s 50-100 years of warming. That means that we are still seeing the effects of emissions from the 1920s. Additionally, some of the CO2, about 20%, persists in the atmosphere for thousands of years. Methane persists for 12 years, nitrous oxide for 114 years, and fluorinated gases from less than one year to 50,000 years. That’s right, the refrigerant, PFC-14 (a.k.a.carbon tetrafluoride) has a lifespan of 50,000 years.

That means the warming being measured today is in part due to the accumulation of GHGs in the atmosphere from the very beginnings of the industrial revolution and that the emissions we are producing today will have a warming effect for generations to come. Even if anthropogenic GHG emissions were immediately brought to zero, the atmospheric concentrations and the life span of the GHGs would continue to increase the average temperature of the plant for decades, if not centuries or millennia to come.

Further reading: here, here and here. And the IPCC chapter here.

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