According to NOAA, carbon dioxide — a key heat trapping gas — increased its atmospheric concentration by 2.77 parts per million during 2016. This was the third fastest rate of increase in the NOAA record following 2015 at a 3.03 ppm annual increase and 1998 at a 2.93 annual increase.
Earlier trends had indicated that 2016 might be on track to beat 2015 as a new record year (and a month by month comparison for the first 11 months of 2016 pointed toward a record rate of rise). These concerns, thankfully, did not materialize as atmospheric rates of accumulation slowed down during December of 2016 — which helped to push the overall year to year comparison lower (NOAA’s year-on-year rate of growth is based on a December to January comparison). Nonetheless, the high rate of atmospheric increase for 2016 remains a matter of concern.
(2015 saw a record annual rate of atmospheric CO2 increase at 3.03 parts per million. 2016’s increase at 2.77 parts per million was the 3rd fastest on record. Overall, the decade of 2011-2016 is presently showing about a 20 percent faster rate of accumulation than the decade of 2000 to 2010. This should moderate somewhat post El Nino. However, Earth System feedbacks threaten to hamper the environment’s ability to take down excess carbon as the world begins to approach 1.5 C warmer than 1880s averages. Image source: NOAA.)
Overall, the average annual rate of increase for the first six years of the decade beginning in 2011 was 2.42 parts per million. This rate is approximately 20 percent faster than during the decade of 2001 to 2010 (analysis based on this NOAA data) at around a 2.05 parts per million annual increase. Prior to the most recent decade, the 2000 to 2010 period showed the fastest rate of atmospheric carbon dioxide accumulation on record.
El Nino, through ocean warming and related land impacts such as increased droughts and wildfires, can reduce the rate of CO2 uptake by the Earth System — thus forcing a higher rate of increase due to the human emission. And the 2015 to 2016 period featured a strong El Nino. All things being equal, we should expect atmospheric rates of increase to moderate somewhat during 2017. Possibly dropping to slightly below 2 ppm in the best case.
(Extremely rapid rates of atmospheric CO2 increase since the mid 20th Century have been driven by ramping rates of fossil fuel burning. Now we are at a point where the Earth System will have more and more difficulty taking in the carbon spewed out by smokestacks and tail pipes. Image source: The Keeling Curve.)
However, global carbon emissions from fossil fuels at near record levels will continue to push a very high rate of atmospheric accumulation of this climate change driving heat-trapping gas. And the added insult due to global warming now ranging above 1 C hotter than 1880s for most years will tend to put a cap on how effective the Earth is at taking in the very large excess human emission.
By comparison, rates of CO2 increase during the last hothouse extinction event — the PETM — were about 10 to 20 times slower than they are today. And it took hundreds of years for atmospheric concentrations of CO2 to equal the same 125 parts per million increase we’ve now experienced in the 136 years since 1880. So the insult to the Earth System produced by fossil fuel burning is currently extraordinarily high and the rate of heat trapping gas accumulation is probably unprecedented for at least the last 66 million years.
(CO2 is the primary gas driving global warming. But it is not the only one. Add in methane, nitrous oxide and other greenhouse gasses and you end up with a total forcing that’s equivalent to 490 parts per million CO2. Video source: Climate One.)
NOAA is now showing that global atmospheric CO2 averages are hitting near 402.5 parts per million. This level will likely increase to around 404 to 405 parts per million by the end of 2017. The forcing from this CO2 alone (not including methane and other greenhouse gasses which has pushed CO2 equivalent forcing to around 490 parts per million) is enough to push global temperatures to nearly 2 C warmer than 1880s averages this Century (prediction based on ECS model analysis). Longer term, if atmospheric CO2 concentrations remain so high, overall warming could hit 3 C to as much as 4 C hotter than 1880s values when adding in the long-term impacts of other greenhouse gas emissions (prediction based on a meta-analysis of paleoclimate temperature and atmospheric carbon proxies).
With global temperatures already driven to about 1.2 C hotter than 1880s during 2016, it’s not an understatement to say that a period of more dangerous and harmful climate change — forced upon us by the world’s extremely high rate of carbon emissions — is already upon us. And we can see that in the various severe weather and geophysical events that are currently ranging the globe. The urgency for cutting carbon emissions, therefore, could not be greater.
Hat tip to Shawn Redmond
Hat tip to Suzanne