Wolfgang Knorr – Let us move on from ‘net zero’

A plead for a renewed ‘zero emissions’ commitment

Wolfgang Knorr is a Senior Research Scientist for Physical Geography and Ecosystem Science at Lund University

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On Earth Day of April 2021, James Dyke, Bob Watson and myself published a widely discussed article entitled ‘Climate scientists: concept of net zero is a dangerous trap’. The article was then widely shared, and gathered as many as 16,000 likes on Greta Thunberg’s own retweet of the story . But it was also contested, because many people felt it would undermine climate mitigation efforts to bring emissions effectively down to zero. This discussion recently flared up again after the article has been awarded the price for best climate commentary by Covering Climate Now .

This discussion is important, and it is regrettably still largely confined to social media. This is my attempt to clarify a number of important issues, and make a suggestion on how to move on. It is crucially related to where we are now in terms of climate policy, and how we deal with the continuing reluctance of adequate mitigation measures.

Three Phases of Climate Discourse

The prevailing discourse in climate policy has now moved into its third stage. The first stage was characterised by the pledge of the United Nations’ Framework Convention on Climate Change (UNFCCC) to “avoid dangerous interference with the climate system”, that came into force in March 1994. The second stage began with the signing of the Paris Agreement in December 2015 , and replaced the goal of avoiding danger by a temperature target of “well below 2C”, ideally 1.5. While the need to reduce the human impact on atmospheric CO2 to zero was recognised then, the required carbon budgets were only published in 2018 in the Special Report on 1.5C Warming by the Intergovernmental Panel on Climate Change (IPCC) . Now we are firmly in the third phase, where the focus of climate policy is on net zero targets by countries or corporations, promised for some date in the future, usually in the range of 2045 to 2060.

With each new phase, pledges have become more tangible, but at the expense of lowering the level of ambition. Even the warming of approximately 1.1C to-date has led to some “irreversible impacts on natural and human systems” , which implies that even meeting the most ambitious Paris goal can lead to a violation of the UNFCCC’s “avoiding dangerous climate change” pledge. Likewise, the impression has been created that reaching net zero by mid century would in some way be equivalent to meeting the goal of the Paris Agreement. However, meeting net zero by a fixed date obvious does not say anything about the amount of emissions on the way, so meeting net zero even by say 2045 cannot possibly guarantee 1.5. In fact, the latest IPCC report makes it clear that it has now become virtually impossible to meet the 1.5C goal, except if we allow 1.5 to be temporarily exceeded and provide for substantial amounts of still unproven technologies of massive scale carbon dioxide removal.

So what is now the best course of further action? Is it that the concept of “net zero” is in itself sound, but the problem is the inaction? Or is there a flaw in the very “concept” of net zero. I will try laying out both positions, and then suggest a way to unite both and move forward.

Concept as a Dangerous Trap

This view started the “controversy”, so I will begin with it, being aware that this is the one I tend towards. The central argument here is that the term “net zero” as it is used in policy circles is not identical to what is meant by “net zero” scientifically. From a climate science point of view, the sources and sinks of atmospheric CO2 need to balance out, only then can the climate be stabilised. This concept refers to the balancing of all fluxes, directly from human activities (fossil fuels, deforestation, cement production), and indirectly caused by excess CO2 in the atmosphere, which causes the land and ocean to take up about half the current human-made emissions. If we want to prevent a “dangerous interference with the climate system”, then we even have to move the balance from net emissions to negative, until sources and sinks eventually stabilise CO2 at a lower level than now. The policy relevant “net zero”, however, only refers to those fluxes that are caused directly by human activities, without the CO2-driven land and ocean sinks. Let’s call the scientific concept “total net zero”, and the policy one “human net zero”. 

The problem is that “human net zero” is ill defined. Strictly speaking, it means all sources and sinks minus the land and ocean uptake according to the average of a range of computer model scenarios, commonly referred to as the “natural sinks”. Nobody can break down this theoretical scenario into such detailed fluxes that it is possible to tell which sinks are natural, and which not. For this simple reason, IPCC guidelines make the rather simplistic assumption that uptake in managed ecosystems is always human-made, and uptake in unmanaged forests “natural”, essentially writing a “blank cheque for forested countries intent on continuing to burn fossil fuels” . If all land areas are declared managed, the “human net zero” goal suddenly becomes much easer to reach, with the price payed by further watering down the climate target. The concept of net zero looks simple, but in reality it is very complex and only loosely related to the equivalent scientific concept. Herein lies the first danger with the concept of net zero.

The second danger is hidden behind the word “net”. It refers to an abstract mathematical concept, which says that the sum of a negative and a positive of same absolute size is always the same zero, however large the two. Applied to real world problems, it can lead to catastrophic consequences. These fall into two categories: wholesale ecosystem and livelihood destruction through continental scale application of bioenergy and carbon capture and storage (BECCS) , and the licensing of a further delay of climate action, in particular continued fossil fuel exploration and development . These opposing threats create the situation of a trap: since we now need massive carbon dioxide removal to meet the Paris Agreement’s goal, we don’t know if we want to wish for massive carbon removal to succeed, or fail.

Critique of Concept is Dangerous Distraction

According to this view, there is only one net zero concept, and it is soundly based in science. Even if we initially were to reach only “total net zero”, at which point atmospheric CO2 will stop increasing, this will then lead to a decline in the land and ocean sinks over the continuing decades, so that eventually “total net zero” will be the same as “human net zero”. It therefore does not matter that there is uncertainty around the definition of “human net zero”, as long as there is a genuine effort to curb emissions fast.

The problem with heavy criticism of the very concept of net zero is that it plays into the hands of climate deniers, as it threatens to undermine the hard-won consensus that emissions do indeed need to go to zero, which not long ago did not exist. It may be that the existing net zero pledges are mostly window dressing, but the fact that they exist makes it possible to challenge those who attempt to sneak away from their responsibility. Net zero itself may not be as ambitious as we should be about avoiding dangerous climate change, but it is far better than having no agreement at all. The criticism, without offering any alternative, is also heard mostly by people with already doomist tendencies, leaving them even more desperate and disorientated.

Instead of pointing out problematic details around the definition of net zero, we should concentrate our efforts on the next steps. The discrepancy between ambitious pledges and the lack of immediate action is already widely recognised, thanks to the pressure put on countries and corporations to set targets, and the ensuing scrutiny of their policies and business practices. Organisations like Climate Action Tracker  and Carbon Tracker are doing a terrific job and are investing huge amounts of personal effort. We need to support them as best as we can. But wasting our energies critiquing the application of a sound scientific concept rather undermines their efforts, and is therefore dangerous.

The Reconciliation

As so often in discussions of the “wicked problem of climate change” , there can be seemingly opposing viewpoints that are both true. Since the problem of planetary heating and its solution is so difficult, it may be crucial to hear them all, come to an understanding that embraces all of them, and then proceed to act. Here we are dealing with one such case.

Both viewpoints, that net zero is dangerous, or its critique, seem to be situated at two ends of a spectrum that might be characterised by marked pessimism (if we don’t rock the boat nothing will happen) or optimism (don’t stir the horses while action is coming). The reality is probably a mix of both.

The way forward I would suggest is to first accept that the concept of net zero has been deeply engrained in the current policy process, and therefore the first step is to ensure that it happens with minimal harm . At the same time, minds need to be set more forcefully on the goal of immediate emissions reduction and transitioning away from fossil fuels. The concept of “net zero” is not suitable for that, as it draws attention not to the emissions, but to the “trick” of continuing with fossil fuel use thanks to the principle of “net emissions”.

We therefore need a fourth phase of climate policy with a new guiding principle, which I suggest should be “zero emissions”. The way “net zero” is a shorthand for “net zero disregarding natural carbon fluxes”, “zero emissions” will be a shorthand for “near zero emissions, with limited provisions for compensation by sinks”. One advantage is that the word “emissions”, as it is commonly used, does not apply to the natural fluxes.

When we breathe in, we take in CO2, when we breathe out, we exhale it. We do not normally call that an ’emission’. A land ecosystem does the same thing in a day-night and winter-summer rhythm, and likewise this is not a process that is normally thought of as an ’emission’. The same applies to the oceans where we have regions of CO2 uptake and drawdown because of the way the ocean currents flow around the globe. Therefore, as a rallying slogan, “zero emissions” focusses the mind immediately on taking action on human emissions, and does not allow hiding behind carbon sinks in forests and other ecosystems. It also focuses on the zero, while allowing for exceptions to the rule where carbon emissions prove impossible to abate. It thus puts the order of priorities right: first reducing emissions by efficiency gains and avoiding unnecessary consumption and waste, then investing in renewables, and only at last compensating for the remaining emissions through sinks. ‘Net zero”, by putting first the word “net”, does the exact opposite.

To illustrate this point, I would like to suggest you carry out an experiment: after reading this article and possibly following up on various links and threads around it, take five minutes to simply sit with the idea of ‘zero emissions by 2050’. See what associations or images come to you, what feelings it invokes. Then do exactly the same, but meditate on the words ‘net zero by 2050’. See the results for yourself, and appreciate that such associations and images are indeed a very large part of the concept of either of the two terms – and the narrative power they develop in the policy field.

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