Are Negative Emissions Positive?

Geoengineering, climate change, and public perception.

by Sophie Gill


Since 1947, Nuatambu in the Solomon Islands has lost 51 percent of its land area. That’s over half of the island gone since the middle of the last century. From 2011-2014, ten families were forced to relocate because of sea-level rise resulting from global warming. For the most economically disadvantaged, this relocation has been to temporary housing in areas of Nuatambu that are increasingly vulnerable to further encroachment of the sea. Five other inhabited islands in the Solomon archipelago have been subject to the same fate. This is not a phenomenon specific to this area. Climate refugees exist in pretty much all low-lying coastal areas around the world, from the Pacific Islands to the Gulf of Mexico. Though the effects of global warming may appear distant for many, the futures of small, poor, island nation states are inextricably tied to climate change.


‘Negative emissions’ refers to the intentional removal of carbon dioxide from the atmosphere to combat global warming. Most IPCC emission scenarios that keep warming below 2o°C (the stated target of the Paris Climate Agreement) involve some form of negative emissions.

Even if we completely ceased the burning of fossil fuels tomorrow, we would still be committed to ~0.6°C of further warming, due to the inherent time lag within the climate system. This is because there is a delay between the time carbon dioxide enters the atmosphere, and the time it takes to heat up the oceans. Yet, given our heavy reliance on fossil fuels as an energy source, to suddenly halt emissions is a completely unrealistic scenario. Nevertheless, it does illustrate clearly that reducing our emissions alone is not enough to keep to the Paris agreement.


In order to stay below 2o°C, we need to physically remove carbon dioxide from the atmosphere. Various Carbon Dioxide Removal (CDR) schemes have been proposed, many of which aim to mimic or accelerate natural processes which already draw down atmospheric CO2, either in very small amounts, on very long timescales, or both. One example is enhanced weathering. Over million-year timescales the weathering of silicate and carbonate rocks draws down atmospheric carbon dioxide to be stored within the oceans. This acts as a negative feedback on carbon emissions within the carbon cycle and prevents ‘runaway’ greenhouse climate effects. On an annual basis, weathering only sequesters roughly three percent of the carbon that humans emit. Enhanced weathering schemes aim to speed this process up and to draw down atmospheric CO2 on timescales that are useful to humans. Other CDR schemes include Carbon Capture and Storage (CCS), enhanced weathering, ocean fertilisation, ocean alkalinity enhancement, and Bio-Energy with Carbon Capture and Storage (BECCS), to name but a few.


In theory, CDR schemes could help us to keep within the warming limits defined by the Paris Agreement. Some CDR methods could even bring additional benefits. Namely, those involving enhancement of ocean alkalinity could potentially also reverse ocean acidification, allowing coral reefs to recover. However, scientific research into CDR is still in its infancy, with implementation a long way off. Large uncertainties around knock-on environmental feedbacks, economic costs, raw material availability, and scales of deployment still require thorough investigation. Aside from further scientific research in these critical areas, progress must be made towards understanding public perceptions and the socio-political impacts of negative emissions schemes.


It is crucial that policy-makers, scientists and the public together consider why we might need carbon dioxide removal, and develop technologies responsibly to minimise negative social and environmental repercussions.


The tightrope of public perception


CDR is a type of geoengineering, as it would entail deliberate large-scale intervention in the earth’s natural systems for the purpose of counteracting climate change. It’s a loaded term — much more so than ‘Carbon Dioxide Removal’. Geoengineering remains a highly controversial issue — making public perception a tricky tightrope to walk for both scientists and policy-makers.


Why? Many people disagree with interference in natural systems and worry that we may lose control over the climate even more than we currently have. A common argument is that negative emissions would only be treating the symptoms, not the causes, of climate change; if the cause (excessive greenhouse gas emissions) is not treated, then how can we ensure our response to climate change is sustainable? There is also the moral objection that taking a decision to intervene in our climate in this way is an unacceptable domination of future generations by the present generation.


“It would be unjust... to not at least consider negative emissions as part of the solution to climate change.”

These are legitimate concerns, but a distinction should be made between the development of these technologies and their deployment. The latter is not possible until much more of the former has been conducted. There is no immediate threat of interference with our current climate or loss of control. In an ideal world we would reduce our emissions to a level where no geoengineering was required to actively remove atmospheric greenhouse gases. Sadly, we’re already committed to significant further warming even if we substantially reduce our emissions due to the time lag between when emissions occur and when atmospheric greenhouse effects are realised. Even then, the behavioural and institutional changes required to reduce our carbon emissions would require time. Thus, to avoid further exacerbation of ocean acidification, rising sea levels, loss of biodiversity and other impacts of climate change, we must accept the reality that geoengineering might be our best shot. It would be unjust to future generations to not at least consider negative emissions as part of the solution to climate change.


Socio-political critiques


Some critiques of negative emissions are more difficult to address. Geoengineering presents a moral hazard: an insurance against damage that gives rise to riskier behaviour. Negative emissions could allow us to remain closer to the ‘business-as-usual’ scenario, shrinking our incentive to reduce carbon emissions. Realistically, it is unlikely that negative emissions would ever be achieved on a scale to completely offset our carbon emissions. Perhaps, then, it does not present a full moral hazard, as reducing emissions from human activities would still be necessary regardless.


On the flip-side, negative emissions could perhaps present a reverse moral hazard. Motivated by scepticism around geoengineering, people may more seriously consider the carbon footprints within their own lifestyles and how they might individually reduce consumption behaviours. Some climate advocacy groups, such as the 10:10 campaign, suggest that it is possible to cut your personal carbon footprint by ten percent in one year simply through lifestyle changes. This includes things like lowering energy usage in your home, using public transport instead of driving and eating less meat. In many ways though, these individual behaviour changes will only make a minuscule dent to overall global emissions without corresponding systemic changes to the current global economic order. It will be the role of not just governments, businesses, and NGOs, but also the public — through pressure to governments and markets — to drive these changes.


Moreover, climate mitigation measures such as CDR are often also controversial because their impacts are local and uneven. The effects of climate change already disproportionately affect small, poor, island nations and this bias may be exacerbated by geoengineering schemes. Impacts from CDR techniques could be unfairly distributed, particularly in developing nations. Negative emissions could lead to a new form of ‘environmental dumping’, where analogies can be drawn with the disposal of undesirable wastes near poorer populations. For example, with CCS (Carbon Capture and Storage), companies or governments from developed countries could pay developing countries to allow them to store carbon in depleted oil and gas reservoirs. This could be justified as mutually beneficial to both parties; carbon concentrations in the atmosphere are reduced, and the developing country makes a profit. Yet, scales of risk matter here. While risks are not well-characterised for CCS yet, and are mainly speculative, it can be surmised that risks to the host country of the carbon stores would be greater than those of others. If something went wrong, globally this could release a large amount of CO2 to the atmosphere, causing a huge amount of environmental damage. On a local scale, elevated CO2 concentrations might present a threat of unconsciousness or death, drinking water might be contaminated from enhanced acidity and toxic metals, or earthquakes might be induced through fracturing. Is it justifiable that the countries that historically have not contributed anywhere near as much to climate change end up as the dumping grounds for the global North’s mess?


An extension of this argument is that negative emissions could lead to new social injustices, with the wealthy carrying on living their lives of high consumption and emission, and the impacts of actively removing their waste only felt by those far away, reproducing privilege and global inequalities. In decision-making processes concerning geoengineering it is difficult to conceptualise how all stakeholders could possibly agree. If no conscious effort is made it may be that the rich and powerful end up calling the shots.


Where does this leave us?


Despite the serious nature of these critiques of geoengineering they do not mean that negative emissions should be put on the back-burner. Numerous social sciences studies have shown the willingness of the public to engage in issues surrounding geoengineering and strong agreement between concerns of the public (at least those believing in the reality of climate change) and concerns of the scientific community. ‘Business-as-usual’ IPCC scenarios for emissions (no curbing of current emission trends, no negative emissions) are received poorly by the public. There is no question that the desire for change is here.

Action must be better than inaction, and negative emissions will likely comprise one part of the whole package of response to climate change. It is clear that further scientific research is needed, and that there are myriad socio-political issues that need to be considered in tandem with the science of carbon dioxide removal. The only way this will be achieved is through effective dialogue between policy-makers, the scientific community and the public. While combatting climate change is a complex issue, the simplest way to start solving it is to engage in the debate. No solution will ever be perfect, but we can’t carry on as we are. At least with geoengineering, hope still exists for staving off some of climate change’s most devastating impacts.


- To find out more about geoengineering, see the Oxford Geoengineering Program, the New Yorker's "Can carbon-dioxide removal save the world?", The Economist's "Greenhouse gases must be scrubbed from the air", and "What they don't tell you about climate change".


Illustration by Rory MacLean


Sophie Gill reads a DPhil in Earth Sciences at Linacre. She works on the ocean's biological response to geoengineering techniques.

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