No turning back: On the effectiveness of artificially removing emitted CO2 from atmosphere for remediating climate disruption

A new paper, by Tokarska and Zickfeld, just published in the Institute Of Physics (“IOP”) Environmental Research Letters examines the question of what happens to climate change and disruption should, at some time, we collectively decide it’s too bad and deploy, at huge expense, a system of removing CO₂ from atmosphere to, say, get it back to 350 ppm CO₂. The paper is open (not behind a paywall).

In short, there’s no turning back: Once the damage to climate is done by emitted CO₂, especially at the rates with which people are emitting CO₂, the damage to warming and oceans is done, and won’t go away for centuries and centuries. The upshot is if you don’t want the damage, don’t put the CO₂ there in the first place. No technology will fix it. Replanting forests won’t fix it. Managing forests better won’t fix it.

The Abstract:

Artificial removal of CO₂ from the atmosphere (also referred to as negative emissions) has been proposed as a means to restore the climate system to a desirable state, should the impacts of climate change become ‘dangerous’. Here we explore whether negative emissions are indeed effective in reversing climate change on human timescales, given the potentially counteracting effect of natural carbon sinks and the inertia of the climate system. We designed a range of CO₂ emission scenarios, which follow a gradual transition to a zero-carbon energy system and entail implementation of various amounts of net-negative emissions at technologically plausible rates. These scenarios are used to force an Earth System Model of intermediate complexity. Results suggest that while it is possible to revert to a desired level of warming (e.g. 2 °C above pre-industrial) after different levels of overshoot, thermosteric sea level rise is not reversible for at least several centuries, even under assumption of large amounts of negative CO₂ emissions. During the net-negative emission phase, artificial CO₂ removal is opposed by CO2 outgassing from natural carbon sinks, with the efficiency of CO₂ removal—here defined as the drop in atmospheric CO₂ per unit negative emission—decreasing with the total amount of negative emissions.

Supplementary data are available.

This is another investigation which independently affirms an earlier study. Carbon dioxide capture may stop warming, but it doesn’t reverse it, not on any planning horizon which is reasonable.