Myles Allen’s latest paper (Geological Net Zero and the need for disaggregated accounting for carbon sinks | Nature), published in Nature on November 18, is a game-changer for climate change policies. Here are the highlights:

  1. Our current international CO2 accounting systems and policies are “cheating.” We’re counting passive uptake (from forests and oceans) when we shouldn’t be, because these methods aren’t going to keep temperatures from increasing, possibly for centuries
  2. We need to figure out a way to actively remove CO2 from our atmosphere at scale—as in, aiming to remove as much fossil fuel pollution as goes into to our atmosphere—in order to reach a stable net zero future
  3. To do otherwise is irresponsible, and if we don’t do this, we’re playing with fire (because we simply don’t know what will happen if temperatures increase too much).

Preface to Dr. Allen’s paper

Achieving net zero global 53 emissions of carbon dioxide (CO2), with declining emissions of other greenhouse gases, is widely expected to halt global warming. CO2 emissions will continue to drive warming until fully balanced by active anthropogenic CO2 removals. For practical reasons,however, many greenhouse gas accounting systems allow some “passive” CO2 uptake, such as enhanced vegetation growth due to CO2 fertilisation, to be included as removals in the definition of net anthropogenic emissions. By including passive CO2 uptake, nominal net zero emissions would not halt global warming, undermining the Paris Agreement. Here we discuss measures addressing this problem, to ensure residual fossil fuel use does not cause further global warming: land management categories should be disaggregated in emissions reporting and targets to better separate the role of passive CO2 uptake; where possible, claimed removals should be additional to passive uptake; and targets should acknowledge the need for Geological Net Zero, meaning one tonne of CO2 permanently restored to the solid Earth for every tonne still generated from fossil sources. We also argue that scientific understanding of net zero provides a basis for allocating responsibility for the protection of passive carbon sinks during and after the transition to Geological Net Zero.

Key points:

  • “Even if atmospheric concentrations were stabilised immediately, the most likely eventual warming would still exceed 2°C, so simply reducing the net flow of CO2 into the atmosphere to zero is not sufficient to limit warming to below 2°C.”
  • In addition, even if all passive uptake (through forests, oceans, agriculture) were claimed as removal (as is currently allowed), this reduction would be sufficient to stabilize atmospheric concentrations of CO2 but warming would continue for many centuries.
  • Without reducing warming, our models of what will happen to Earth become progressively uncertain at higher warming levels. So, “Ultimately, the only way to minimise the amplifying effect of Earth system feedbacks is to minimise peak warming.”
  • “Until it can be shown that total CO2 uptake by the biosphere and oceans is large enough to halt CO2-induced warming, it is dangerously optimistic to assume that there will be additional capacity…to compensate substantially for ongoing fossil fuel emissions.” In fact, “In a durable net zero world, 100% of the CO2 generated by any continued fossil fuel or fossil carbonate use will almost certainly need to be either captured at source or recaptured from the atmosphere and committed to geological-timescale storage.”
  • “This implies, in addition to reducing emissions, achieving a 10% geologically stored fraction by the mid-2030s and investing now for a further ten-fold increase in stored fraction over the following 20 years, including demonstrating secure and verifiable geological CO2 storage capacity to match any new fossil fuel reserves. These are ambitious but achievable goals for the fossil fuel industry and its customers.”

AI-generated summary

Myles Allen’s recent “Nature” paper on carbon emissions, titled “Geological Net Zero and the need for disaggregated accounting for carbon sinks,” argues that achieving true “net zero” requires not just balancing current emissions with carbon removal technologies, but also actively removing past carbon emissions from the atmosphere by storing them underground, essentially reaching a “geological net zero” to halt global warming effectively; this means that any future carbon extracted from the Earth must be captured and stored permanently.

Key points about the paper:

  • Focus on “Geological Net Zero”: Allen emphasizes that relying solely on natural carbon sinks like forests and oceans to absorb future emissions is insufficient, and actively removing historic carbon emissions is necessary to achieve true climate stabilization.
  • Implications for Net Zero Targets: This research suggests that current “net zero” targets might not be stringent enough if they don’t explicitly address the need for carbon capture and storage to address past emissions.
  • Importance of Accounting for Carbon Sinks: The paper calls for more detailed accounting of carbon sinks to accurately assess the effectiveness of mitigation strategies.