How ‘net zero’ sidelines equity when it comes to flying

Abstract

The catastrophic impacts from storm Boris in 2024 remind us that emissions from our energy use remain too high. Updating a climate science lecture, I added 3 ppm to the CO₂ concentration graph reflecting last year's data and will again talk about record-breaking temperatures. Yet in 2015 the Paris Climate Agreement signified a hopeful breakthrough, reinforcing the importance of equity, and strengthening ambition for urgent climate action. It recognised the scale of the challenge and led to declarations of a climate emergency. So where did we go wrong? There are many responses to this question, and I’m not attempting to claim this commentary has the answers. Nevertheless, having followed the debate around two ‘difficult to decarbonise’ sectors, I illustrate how sidelining ‘equity’, combined with a techno-centric approach to deliver ‘net zero 2050’ targets, leaves the global majority facing a bleak future; but one that we have the wherewithal to turn around.

Aviation and shipping – an illustration of inequity

Tackling emissions from aviation and shipping is routinely placed in the ‘too difficult’ box. From a policy perspective, emissions arising from flights within countries, and from inland and national coastal navigation, are grouped in with other sectors when it comes to climate change mitigation and policy mechanisms. So far, so good perhaps? Not so. Aside from the technical challenges around cutting their emissions that I will come onto later, unfortunately, most of these sectors’ emissions, generated when flights or ships emit into international airspace or waters, do not fall under national jurisdiction. The magnitude of these ‘international’ emissions, when considering even just the CO₂, would place them around sixth in the world after Japan, if they were ranked against nations (Friedlingstein et al., 2023).

The bodies with responsibility for cutting this very large share of global emissions are the International Civil Aviation Organisation (ICAO) and the International Maritime Organisation (IMO). They are charged with developing policies and plans of action with their member states. Over the decades, this has led to significant inertia, as, unlike mitigation action within national boundaries, the ICAO and the IMO must agree on targets and plans with diverse international constituents (Abeyratne, 2024); constituents that within the United Nations Framework Convention on Climate Change, are recognised as having ‘common but differentiated responsibilities and respective capabilities’ (UNFCCC, 1992). The result of this arrangement has been growth rates in these international emissions that collectively exceed the global average. This leaves them typically increasing their absolute, and, their share of global emissions, year-on-year (Friedlingstein et al., 2023). This is a situation that might be expected for a less developed nation aiming to tackle poverty and improve well-being through rising energy use; not one from technically mature sectors that disproportionally serve the global population.

Specifically, nearly two decades since the Kyoto Protocol was ratified, aviation remains without a sector-wide obligation to cut emissions – agreeing only in 2022 to a long-term ‘aspirational’ goal of net-zero emissions in 2050 (ICAO, 2022). While some argue that this signals an improvement on their previous emphasis on offsetting, in practice the agreement has no teeth, with weak statements around ‘further developing’ tools to quantify emissions, or ‘creating finance mechanisms’ to support initiatives in developing countries (Mital and Rutherford, 2023). Such an approach appears far removed from the notion of a climate emergency.

The IMO, unlike the ICAO, has established a suite of mandatory measures. In 2018, it set a 50% CO₂ target for the sector by 2050, subsequently updating it to ‘net-zero’ greenhouse gas emissions by ‘around’ 2050 (IMO, 2023). Importantly, from a climate science perspective, and unlike ICAO, it recognises the need for short-term emission reductions (Bullock et al., 2024), as it is the cumulative emissions that matter, and not the level they reach in 2050. As such, it has set a 20% cut (‘striving for 30%’) in 2030 and a 70% cut by 2040 (‘striving for 80%’) compared with 2008. The detail of implementation continues to be discussed. Nevertheless, if the ‘strive’ target becomes the focus, and the ‘net’ element does not end up being the dangerous distraction it has become elsewhere, then the shipping sector will start to get to grips with the challenge at hand.

Turning to ‘net-zero’ then, in my own view, it is the ‘net’ in ‘net-zero’ that leads me to again add 3 ppm to my CO₂ concentration graph, and yet to see the scale of CO₂ reductions that past analysis highlighted was needed to avoid a 2°C rise (Anderson and Bows, 2008). The problem with this terminology is that it gives the impression that any sector finding emission reductions difficult, has options to turn to others to reduce emissions on their behalf or rely on some form of carbon dioxide removal (CDR). This could be through trading, a ‘nature-based solution’, or a form of ‘negative emission technology’ (NET). NETs and wider CDR include a multitude of mechanisms from direct air capture, and biomass with carbon capture and storage, through to afforestation and soil mineralisation (Pires, 2019).

Agriculture is an illustration of a sector that will struggle to cut its own emissions in line with Paris goals. Nitrous oxide (N₂O) and methane (CH₄) are both generated through agricultural production for a growing population and to support Sustainable Development Goal 2: zero hunger. Technologies and practices can mitigate these emissions to a degree, but the N₂O emissions in particular, produced when fertilisers are added to improve growth, will be some of the most difficult to cut (Feng and Li, 2023). Given many people around the world currently do not have sufficient access to good nutrition, the inclusion of ‘equity’ within the Paris Climate Agreement will necessitate deeper cuts in other sectors to support food security if, as looks likely, mitigation in agriculture continues to be more limited than in most other sectors. This is an immense challenge, especially given that NETs are either not currently operating at a large scale, or that options such as reforestation, rely on the long-term stability of the climate to securely lock carbon into new forests; a clear risk given the direction temperatures are heading (Jager et al., 2023). There is also evidence that the discourse around CDR is in practice delaying climate action (von Rothkirch et al., 2024). Nevertheless, if the Paris Agreement remains the goal, then large-scale CDR will be needed to at least facilitate an equitable production of food in future. In short, everyone needs to eat, and there are vast inequalities in terms of nutrition worldwide, such that prioritising a sustainable route to CDR for agriculture has a strong moral and ethical case, even if technically this is a huge challenge.

Turning back to shipping, embedding the term ‘net-zero’, is inappropriate to include in this sector's target. In the time left to mitigate emissions to levels consistent with a good chance of avoiding 2°C, all sectors will need to be on a radical transformation pathway. Some will be able to cut emissions a little quicker than others, but few will be making the level of improvements at the pace the science dictates (Anderson et al., 2020). Sectors must focus at least primarily on themselves, minimise the distraction of ‘net’, and push forward with proven and reliable measures that can cut their own emissions.

Alternative zero-carbon fuels for shipping, for example, may be available at scale in coming decades, but in the critical intervening years, other known measures are necessary. A similar argument goes for carbon capture and storage on board ships. Moreover, alternative ‘green’ fuels will likely be more expensive, at least in their early adoption phase, so reducing the amount of fuel consumed, (even questioning the level of consumption), would be a prudent strategy. Options include adopting new operational models and route optimisation to incorporate slow-steaming, rapidly expanding renewable shore power for plug-in electrical power at ports and battery recharge, and crucially, given slow fleet turnover (Bullock et al., 2020) retrofitting energy saving measures, including wind-propulsion technologies (Mason et al., 2023), to meet the sector's 2030 targets and thereby cut cumulative CO₂.

The other side of the shipping story is that in a world successfully mitigating climate change, a large proportion of seaborne trade will no longer be required – around a third of freight transported by sea is fossil fuel, mainly for energy use (Jones et al., 2022). On equity though, shipping facilitates the availability of food and material resources for everyone on the planet. So, while there are inequities in the amount of shipping used around the world, it is a sector that facilitates development and can improve lives in the poorest nations. This, I argue, is not the same for the aviation industry, except in the case of emergency relief.

While ships have a long way to go to improve their energy efficiency, options are available to do this, meaning they can make good headway in a short time. This is not the case for aircraft, as the relative cost of fuel means they are already highly efficient, honed pieces of technology. Incremental improvements continue, through lightweighting, aerodynamic modification and engine refinement, but they are far from sufficient to offset annual growth in passenger-kilometres, meaning that absolute CO₂ emissions continue to rise. They also emit other harmful emissions into sensitive parts of the atmosphere – unlike any other sector – warming the climate at around three times the rate of aviation's CO₂ (Lee et al., 2021).

Compared with shipping, and most other sectors, aviation is highly limited in terms of routes to cut its emissions. There is growing interest in ‘sustainable aviation fuels’ derived from bioresources that can be ‘dropped in’ to planes without changes to infrastructure, and e-fuels generated by combining hydrogen with CO₂ directly captured using renewable electricity. There is also interest in electric aircraft for short-haul flights, and the use of hydrogen either in fuel cells or direct combustion, although these require significant modifications to aircraft. All these options though face significant barriers – both in relation to safety and the scale of fuel required. A scale, equivalent to shipping, yet disproportionally serving a minority of the population. This is where it becomes evident how much we seemingly choose to ignore ‘equity’ within the Paris Climate Agreement. If this sector was critical in supporting global well-being and development, then it would be important to prioritise investment into solutions for its decarbonisation, ahead of others, but is this the case? Most international arrivals relate to leisure travel (World Tourism Organisation, 2018) with flights used by a minority. An estimated 1% of the population produces 50% of the CO₂ from air travel (Gössling and Humpe, 2020), and national surveys highlight that those who travel by air are disproportionately wealthy.

Despite these stark inequities, outputs generated by cost-optimisation models, used widely to inform strategic planning, typically result in this highly inequitable contribution to climate change being labelled as ‘residual emissions’, alongside shipping and agricultural emissions. The argument is that given their emissions are ‘hard to abate’, other sectors must cut their emissions more – including through widespread use of negative emission technologies. By taking these ‘residual’ emissions as a given (e.g. ESO, 2024) governments and those informing decision-making appear unprepared to consider that this highly carbon-intensive activity needs to be mitigated, at least in part, through demand management. Demand management can address the scale and urgency of the challenge at hand while alternative technologies are developed and as part of a plausible ‘emergency plan’ consistent with Paris Climate Agreement goals. Instead, what I find most disturbing is that the use of aviation remains typically unquestioned, placing increasing pressure on other industries to move more quickly, despite its dominant use by a privileged minority. Moreover, the limitations on technical options for mitigating aviation emissions – and not just CO₂ – could lead to prioritising the use of constrained renewable capacity for alternative aviation fuels to serve a wealthy minority of the global population. This suggests to me that ‘equity’ within the Paris Climate Agreement is simply being ignored when it comes to flying.

Conclusion

A failure to genuinely acknowledge the importance of ‘equity’, coupled with a techno-centric approach to the energy system transition, is placing us on a pathway that is at odds with our Paris temperature and equity commitments. A seemingly blind acceptance that frequent air travel is a necessity that must not be interrogated, is surely a stab in the back for poor communities in the global south, struggling with catastrophic and escalating climate impacts. Yet amongst those of us privileged enough to fly, and make decisions about energy policy that will impact others more than ourselves, we appear oblivious to the catastrophe we are seemingly complicit in. Cognitive dissonance or a deliberate attempt to maintain privilege and global inequalities? Time will tell.