Which Net Zero?

22nd December 2022

The global stampede to adopt net-zero climate goals continues unabated. As a goal net-zero is achieved when any residual carbon emissions are counter-balanced fully by dedicated carbon removal. Delivered at a global level, this would stabilise global temperatures. Almost 70% of states (accounting for 90% of the world’s economic activity) have adopted net-zero goals, as have 40% of the world’s largest companies. Does this mean climate procrastination is finally coming to an end?

A lot depends on what net-zero really means. In Which Net Zero, a new paper in Ethics and International Affairs, Chris Armstrong and I argue that there are critical ambiguities in net-zero policy, in particular regarding the scale of residual emissions, and the distribution of impacts and benefits associated with both residual emissions and counterbalancing removals.

The scale of residual emissions really matters. Despite the hype associated with both nature-based and engineered forms of removals, scientific analysis indicates that potential sustainable levels of carbon removal may be as little as 2-5Gt of CO₂ per year (a Gigatonne (Gt) is a thousand million tonnes). To give a sense of the amounts involved, the world produces around 2Gt of steel, 2.7Gt of grain (all cereal crops) and 4.5Gt of concrete each year. But total emissions of greenhouse gases are close to 50Gt of CO₂ ‘equivalents’. Removing 2-5Gt of CO₂ each year is still a big undertaking. Yet if that is to balance residuals in a net zero world, emissions must be cut by 90-95%.

Limits on sustainable removals arise primarily in requirements for land, water, materials and clean energy. Many climate model scenarios involve residual emissions of 10-20 Gt. To balance such levels, removals based on bioenergy with carbon capture and storage (BECCS) would require up to 1000 million ha or three times India’s land area. But other techniques create similar challenges: achieving the same removals through direct air capture would require up to nine times India’s primary energy consumption, for example.

The problems with such a ‘broad convergence’ with lots of removals balancing high remaining emissions are analogous to those of trying to balance two elephants on a seesaw. Not only is it difficult to put elephants on a seesaw, but even if we were to succeed, we would likely end up with a broken seesaw. In other words, trying to achieve broad convergence would put unmanageable stresses on society. Both elephants would impose serious harms, typically distributed unfairly. Delivering large removals would likely drive up costs of food and energy, exacerbating food insecurity and fuel poverty. Leaving large residuals would mean continued harms to health from air pollution and continued impacts from fossil fuel extraction and production.

For all these reasons, and more, we argue that a ‘narrow convergence’ – instead balancing two mice on the seesaw, is far preferable. And since we wrote the piece, empirical research has confirmed serious reasons to worry in this regard. Analysis of countries’ plans submitted under Paris accord by Holly Buck and colleagues found that projected residuals averaged almost 20% (or around 10 Gt at a global level). Detailed examination of the claims on land involved in national climate plans published as the Land-Gap Report (pdf) found these exceed even the worst scenarios for BECCS – already demanding 1200 million ha (closer to four times the area of India). And many corporations have also laid claim to carbon removals in their net zero plans, often promising to offset much higher levels of residual emissions. One analysis found fewer than half of company plans cut residual emissions to less than 10%, and many using emissions-intensity measures that would allow total emissions to grow.

Much recent policy debate has highlighted the need for strong quality and accountability standards for carbon removals. The European Union has published a legislative proposal on certification of removals, albeit with some critical reactions regarding the role foreseen for impermanent land-based removals or ‘carbon farming’. And at COP27 proposed rules for carbon removals in carbon markets were sent back to the supervisory body for more detailed revision, following criticism especially regarding the lack of human and indigenous rights protections. In the private sector a new guide from Shopify on buying carbon removals, sets non-negotiable standards on additionality, verifiability and sustainability.

But achieving narrow convergence means that tough standards will be needed on both sides of the NZ balance. On the one side we must ensure that removals are real, durable, additional, sustainable and fair. But on the other, we must also ensure that the residual emissions ‘legitimated’ as counterbalanced by removals (whether through credit trading or other mechanisms) are genuinely unavoidable and socially necessary.

At COP27 such issues were finally broached, not least as a result of the UN’s High Level Expert Group report on net-zero claims which not only rejected the idea that companies could claim net-zero compliance based on poor quality credits (such as those from non-durable, or non-additional removals), but also highlighted the incompatibility of net zero with new fossil fuel investment, lobbying against climate action and intensity based targets.

Nonetheless there is a desperate need to translate such recommendations into law and policy. Ensuring quality removals is one thing, but given the limits to sustainable removals, it would be deeply unfair and problematic if that capacity were consumed in offsetting luxury emissions for air travel, other high consumption by global elites. Quality removals need to matched to ‘legitimate residuals’.

The Science Based Targets Initiative (SBTI) sets a global cap on legitimate residuals, compatible with Paris – no more than 5-10% of current emissions. But this still leaves the prospect that businesses perfectly able to completely decarbonise might claim 10% residuals and removals; while other businesses creating real social value, but unable to reduce emissions by 90%, might then be treated as not legitimate users of removal ‘offsets’.

Achieving narrow convergence, and fairly matching legitimate residuals with quality removals is a key challenge for climate policy in the coming years. These tasks cannot be left to carbon markets, where the incentives are for more trading (and a broader convergence) lower standards, and for profits before fairness.