The United Nations defines Net Zero as ‘…cutting greenhouse gas emissions to as close to zero as possible, with any remaining emissions re-absorbed from the atmosphere, by oceans and forests for instance.’ You’ve written there are many versions of Net Zero. Would you explain, including any ramifications related to them?

The UN definition of net zero is one of the less problematic ones in circulation. However, it still leaves a lot of wriggle room, and the formal language of climate COP decisions remains even vaguer. I’d highlight three issues.

First, there is both constructive and tendentious debate over how ‘close to zero’ we can get, and which residual emissions are legitimate. Nitrous oxides from fertilizers and methane from rice paddies are genuinely hard to eliminate. Shipping, industrial chemicals, steel and cement might still generate significant emissions in 2050 even if the further spread of zerocarbon options can be anticipated. Air travel is typically seen as hard to abate, but one can question whether its rapid expansion is ‘essential’. And even though decarbonization of both power generation and surface transportation seems inevitable, both oil corporations and petro-states are claiming that net zero is somehow compatible with substantial continued fossil fuel exploitation and consumption, effectively and falsely implying that much fossil fuel use is impossible to eliminate.

Second, definitions of net zero as a state say nothing about the pathway to that state. Cumulative emissions are what matter for the end temperature. The difference between digging coal and pumping oil until , say, 2049, and then suddenly shutting off the taps; and cutting emissions as fast and as soon as possible from 2023 is huge in terms of net climate impact. At a global scale, this would easily make the difference between stabilizing temperatures well below 2°C and as close to 1.5°C as possible, and blowing well past even the 2°C guardrail.

Third, there is also huge uncertainty over how much carbon removal might be practical, just and sustainable, and in what forms. Absorption by oceans and forests sounds pretty innocuous, but these ‘natural sinks’ are already overloaded, and the implications uncertain. Biological carbon removal methods compete for land, while engineered ones would compete for renewable energy. If residual emissions can be cut by 90-95%, there might be sustainable and just removals able to take up the slack. This would imply maybe 2.5-5 gigatons per year of additional, anthropogenic removals of CO2. But at present it seems many states and businesses expect 20% or more of current emissions to continue at netzero, implying more than 10 Gt pa of removals just to balance continuing emissions. Achieving such levels of removals – if even possible - would likely impose high costs, environmental harms, and multiple injustices.

So how we define and pursue net-zero matters intensely for sustainability and justice. As I argue in my paper with Chris Armstrong, we need a rapid descent to a tight convergence with minimal residual emissions and minimal counterbalancing removals. That could spare some sustainable Carbon Dioxide Removal (CDR) capacity to work on ‘drawdown’ – to return atmospheric Greenhouse Gas (GHG) concentrations to long-term safe levels, and ensure no subsequent temperature increases.

What do you consider common myths, if any, concerning the use of tech/renewal energy and nature-based solutions to address decarbonization?

There is a widespread problem of over-reliance on speculative technical responses – a broad political commitment, in Western countries at least, to market-led innovation policy which devalues and discourages, rather than facilitating, behavioral and life-style changes. Epitomized by actors such as Bill Gates, this Silicon Valley ideology leads both to delays in deploying existing technologies, and a delusional belief in the prospect of future technologies such as AI, fusion power, and geoengineering to address climate crisis. Having said that, a similar form of ‘magical thinking’ can often be seen amongst climate activists who tend to overestimate the potential of behavioral change and of so-called ‘nature based solutions’ like restoration of habitats such as forests, peatlands, and sea-grass beds. In my view, the scale and urgency of the climate challenge can only be addressed through radical systemic change. Cultural shifts can be widespread and rapid, but not unless incentives, messaging, technologies, and infrastructures are all aligned. Technology, behavior change, and nature-based measures can all contribute to the systemic transformation we need, but if the underlying system continues to rely on promoting growth and consumption, none of them will be enough … and at present, technological measures in particular risk generating rebound effects or delays to systemic change that make matters worse.

A particularly worrying example of the problem is carbon capture and storage (CCS). As an end-of-pipe addition to power generation and some industrial carbon sources, it has been promised for decades, defending continued development and use of fossil fuels. Major corporations and petrostates still use promises of CCS as a smokescreen for continued fossil exploitation. Activists rightly label it a false solution and a technology of procrastination. Yet in a transformed political economy, it could play a valuable transitional role in speeding decarbonization of industries such as cement and chemicals. The polarized debate over CCS is spreading now to carbon dioxide removal (CDR) technologies. Essential for counterbalancing otherwise recalcitrant residuals such as emissions of nitrous oxide from fertilizer use, or methane from rice paddies, companies such as Occidental, and states such as Saudi Arabia and the UAE are making exaggerated claims about CDR as a means to resist the phase-out of fossil fuels. My past research has calculated that if such promises of CDR are taken seriously, but fail to deliver, this could result in up to 1.4°C additional global heating.. The wisest approach would be to aim for real zero emissions, while also working to develop CDR as a supplementary tool – not a substitute for mitigation.

Some advocate the development of solar geoengineering to reflect a portion of sunlight away from the earth or increase solar radiation escaping away from the Earth to cool it. What are your thoughts on the realistic potential for it to curb climate change? Challenges and possible risks related to it?

It would be fair to say that despite some promising modeling work using earth system models, no one knows whether solar geoengineering could help in practice, when considering the material, social, and political context. There are just so many uncertainties in the projected effects (such as uneven impacts on rainfall), the technical challenges in deployment, and particularly, in the security and geopolitical implications that make global agreement on solar geoengineering implausible. I've just attended the UN Environment Assembly, where countries couldn't even agree on how to gather information about solar geoengineering, never mind how to govern it! As a result, right now, I’d say that any claims about the possibility of using solar geoengineering should be discounted. As the recent Global Tipping Point review concluded: “We strongly caution against reliance on solar geoengineering … or the expectation that this kind of approach will be available and politically acceptable in the future." I worry that hopes pinned on such technologies simply fuel more delay in delivering systemic change to phase out fossil fuels and rapidly cut emissions (a problem called ‘mitigation deterrence’). There’s a case for doing more research, which could help reduce some of the uncertainties (while probably generating new ones) but it must be carefully regulated and governed to minimize risks. Research based on idealized and implausible scenarios of deployment not only fuels delay, but also risks undermining the geopolitical agreement needed to build on the Paris Agreement and rapidly accelerate emissions cuts.

It's also clear that the market-led innovation model for climate action is entirely inappropriate for solar geoengineering and combines harmfully with ill-advised research. In 2023, a commercial US startup, ‘Make Sunsets’, made headlines for trial releases of balloonbased geoengineering intended to justify marketing ‘cooling credits’ on voluntary carbon markets. The claims made by the company verged on the fraudulent, but they were apparently inspired by diverse pieces of academic research discussing the feasibility of such a dispersed launch mechanism, and possible ‘exchange rates’ for radiative forcing
through greenhouse gases and reflective cooling. Even if such a project successfully delivered cooling, the mechanism of funding would mean that it automatically enabled continued emissions with an offsetting effect. In other words ’mitigation deterrence’ would be inbuilt.

What roadmap would you propose to address climate mitigation and adaption?

This is a very big question. But to suggest some broad strokes, the time for waiting and hoping for technological salvation is long past (if it were ever actually an option). Radical measures are essential in mitigation, adaptation, climate finance and carbon removal. Multilateral agreements and national policies should aim to deliver a suite of transformative approaches. A rapid phase out of fossil fuels. Transformation of agricultural systems to support low meat diets and regenerative agriculture techniques. Replanning and redesign of cities on the ‘15 minute principle’ to dramatically cut needs for car use and ownership and to manage urban heat levels through better design and urban greening. Widespread habitat restoration led by local communities and Indigenous Peoples. Managed retreat in the face of rising sea levels. Reversal of global financial flows to deliver massively increased finance for clean energy, urban transit, forest protection, and adaptation on fair terms, including large sums in the form of reparations for past extractivism, and for ongoing loss and damage. Technology transfer on preferential and patent free-terms for carbon removal, clean energy and other essential technologies. Industrial policies designed to rapidly grow essential industries, if necessary, within the public sector. And, research into safe, just and sustainable ways to use global or regional cooling techniques (e.g., for protection of vulnerable coral reefs).

In terms of carbon budgets, the heavy lifting will have to be done by mitigation, reducing global emissions by over 90%. The power sector will need to be carbon free. Surface transport will be largely electric powered, but with a focus on shared transit rather than individual electric vehicles. Buildings will be heated and cooled with zero-carbon electricity. Agriculture will have residual emissions, notably from fertilizer, but reduced animal raising will mean less methane, and agricultural land management will incorporate carbon removal techniques such as enhanced weathering and agroforestry. Heavy industry will also likely have residual emissions, counterbalanced by the deployment of engineered carbon removal techniques. Together forms of carbon removal at maximum might be equivalent to 10% or so of today’s emissions. Further climate impacts remain inevitable, and thus deals on finance for adaptation and loss and damage will be critical, as will improved freedom of movement for those in the most vulnerable locations.

Underpinning all of these is a case for systemic transformation in the global political economy to ensure that climate measures work to empower, not further burden, disadvantaged, precarious, and vulnerable groups in both the global South and global North. This requires international alliance building between progressive actors to resist and reverse the current trends towards authoritarian, antienvironmental populism and nationalism, and instead to extend action on decolonization and climate justice. As the recent report on global tipping points concluded, in the face of tipping events that will impact climates for millennia, the only reasonable responses are those which drive social transformation towards radical emissions reduction. And delivering such responses starts with global climate justice.

Duncan McLaren is a Postdoctoral Climate Intervention Fellow in Environmental Law and Policy at UCLA School of Law. His research lies in climate politics and governance, especially with respect to geoengineering technologies and interventions. He previously worked as a Research Fellow and Professor in Practice at Lancaster University (UK) focusing on the security politics of climate engineering, and on governance of net-zero and the role of carbon removal techniques.

He received his first class B.A. in Geography from Cambridge University (UK), and also holds Master’s degrees in Environmental Policy (University of London) and Business Administration (Cambridge). He worked for many years in environmental advocacy, most recently as Chief Executive of Friends of the Earth Scotland from 2003 to 2011. His Ph.D. at Lancaster University examined the justice implications of climate geoengineering.

Dr. McLaren’s publications on climate politics, environmental justice, sustainable cities and more include books with Routledge/Earthscan and MIT Press, and papers in Nature Climate Change, Global Policy, Energy Research & Social Science, and Anthropocene Review, among others. His personal research website can be found at www.duncanmclaren.net.