How long will anthropogenic (man made) CO2 remain in the atmosphere?
It is an easy question to ask. There is no simple answer, although ‘forever’ is a good and somewhat terrifying approximation. However, it partly depends on how fast we emit the CO2 and at what concentration we stop emitting CO2. “Equilibration among the various carbon reservoirs of the atmosphere, the ocean and the terrestrial biosphere occurs on timescales of a few centuries” say David Archer et al. at the University of Chicago29.
There is considerable variation amongst the mathematical models available. Archer et al. note that “a sizeable fraction [20-35 per cent] of the CO2 remains in the atmosphere, awaiting a return to the solid earth by much slower weathering processes and deposition of CaCO3 [calcium carbonate30]”. Or, to put it another way, a recent paper in Nature31 suggests that mankind has effectively cancelled the next one and maybe two ice ages. Our carbon footprint already extends hundreds of thousands of years ahead of us!
Simulation of the effect of a 1 trillion tonne pulse of CO2 (which in effect is pretty much what we are doing today) yields a form of decay that illustrates the two mechanisms Archer et al. describe. The predictions are shown below.
Simulating our 1 trillion tonne pulse of CO2 into the atmosphere (Archer et al, 2009).
These decay curves were approximated by Predict Ability Ltd to produce a function of CO2 with time, following the sudden (artificial) cessation of emissions. The predicted CO2 concentrations were then converted into estimated temperature anomalies32 to see how long the loss and damage caused by the emissions would last. The answer, in practical terms, is for thousands of years. Possibly one third to one half of the CO2 that was produced by Newcomen’s engine in 1712 is still up there somewhere in the atmosphere.
The above article is taken from Predicting the Price of Carbon – How to Crack the Climate Change Code for Good.
32 CO2 concentration/ppm ~ 316 × exp( Tanomaly / 3.61 )
Author: Edward Coe
Edward Coe is Managing Director and co-founder of PAL. He has extensive experience of systems development and implementation for advanced derivative trading systems utilising a broad range of technologies supporting in house, bespoke and third party software. Edward developed the software behind PAL Carbon.