Climate change has become a much more salient issue for publics around the world over the past few years with the highest recorded temperatures being set and an increase in events such as heatwaves, flooding, drought, and wildfires. Unless rapid and challenging policy changes are made, it is unlikely that the aspiration of the Paris agreement to limit global average temperature increase to close to 1.5 °C will be achieved (IPCC 2018). In particular, in order to approach a goal of net zero carbon emissions, urgent action across all levels of society is required, action which is likely to include at least some use of Carbon Dioxide Removal (CDR) technologies (National Academy of Sciences, 2019; Ripple et al., 2019; Royal Society and RAEng, 2018). The current study examined public understanding and risk perceptions of terrestrial enhanced weathering (EW), a potential CDR strategy that is currently being researched as part of approaches to reduce climate change. There are several different forms of enhanced weathering, but this study focused on application of silicate minerals (e.g. basalt) onto agricultural land, an approach which has gained considerable scientific and media attention in recent years. Biogeochemical reactions within soil ecosystems transform atmospheric carbon dioxide into carbonates, which become sequestered in soils and the oceans on a long-term scale. Some estimates suggest such terrestrial weathering could indeed, if applied at global scale, contribute significantly towards global CDR goals (Beerling et al., 2020; Kelland et al., 2020). Aside from removing carbon dioxide from the atmosphere, terrestrial enhanced weathering may have co-benefits including slowing ocean acidification, benefitting croplands, and improving soils (Hartmann et al., 2013; Beerling et al., 2018). Research has shown that in controlled environmental settings, adding basalt to crops increased soil potential to store four times as much carbon dioxide and also increased crop yields by up to 20% (Kelland et al. 2020; Beerling et al. 2020). However, there are numerous considerations that are likely to affect the efficiency and feasibility of enhanced weathering as a sequestration technique. For example, there are high energy costs associated with mining, grinding, and spreading minerals, thereby reducing the potential for net CO2 removal (Moosdorf et al. 2014), with these processes likely having additional environmental and ecological consequences. There are also a range of ethical and social concerns; most of which are also common to other CDR strategies, including spatial and inter-generational inequalities in the risks associated with deployment. For example, those living where this strategy is likely to be most effective at scale (e.g. in countries in the Global South) are the least responsible for historical emissions (Cox et al., 2018; Lawford-Smith and Currie, 2017).
Many CDR approaches, including terrestrial enhanced weathering, have uncertainties over their environmental impacts, potentially altered ecosystems, financial costs, and the need for land and space to build facilities and store emissions (Lomax et al. 2015). CDR approaches range from established land-use change such as afforestation or peatland restoration through to more novel strategies including bio-energy with carbon capture and storage (BECCS), enhanced weathering, or even direct chemical capture of CO2 from the air (Fuss et al. 2016). Many of these technologies are still in the very early stages of development, with enhanced weathering currently undergoing field-scale research trials. For new technologies, recommendations for ‘upstream engagement’ demonstrate that constructive societal dialogue should be carried out while research and development are still in the early phases, with deliberations amongst relevant parties helping to shape technologies, identify concerns, and inform decision-making (Wilsdon and Willis 2004; Rogers-Hayden and Pidgeon 2007; Macnaghten 2020). Currently there is limited public awareness and even less research into public perceptions of CDR approaches and technologies. It is clear that if these technologies are ever to be deployed at scale, a range of ethical, legal and moral issues will first need resolution, and many of these issues will impact upon societies and publics (Corner and Pidgeon 2010; Cox et al. 2018). Accordingly, inclusion of public voices in debates about CDR is essential to determine preferences for these emerging technologies, to assess what might influence public acceptability and support, and to ensure that any innovation pathways and governance systems adopted are responsive to societal concerns (Parkhill et al., 2013; Pidgeon, 1998; Rayner et al., 2013).
The CDR strategies described above are commonly defined as a sub-set of ‘geoengineering’, which refers to deliberate large-scale manipulation of the Earth’s climate that could either be through solar radiation management (SRM) or carbon dioxide removal (CDR) (Royal Society, 2009). SRM technologies involve reflecting sunlight back into space away from Earth and are considered particularly controversial because of their significant uncertainties and possible environmental consequences, as well as the fact that they do not directly reduce CO2 (Bellamy et al. 2013; Pidgeon et al. 2013). There is not one broad public perception towards climate engineering but a range of possible responses depending on the specific technology type, its governance arrangements, and associated risks and challenges which will vary for each. It is important that these strategies should be considered separately, and broad categorisations avoided, such that public discourse and governance can be made more useful and relevant to future decisions about specific strategies (Colvin et al. 2020). As research into many of the more ‘upstream’ approaches is still in its initial stages, it is necessary to ascertain what shapes public perceptions of climate engineering and emerging technologies to help predict what could help inform public understandings of individual technologies and proposals.
Early work into public perceptions of climate engineering has shown generally low levels of awareness, with some evidence that those who are more concerned about climate change are more supportive of climate engineering (Pidgeon et al., 2012). In addition there is commonly a preference for CDR methods over SRM (Pidgeon et al., 2012; Scheer and Renn, 2014). Some of the previous literature has focused specifically on SRM, generally showing low levels of acceptance and support (Mercer et al. 2011; Macnaghten and Szerszynski 2013; Visschers et al. 2017), with risks generally perceived to be greater than benefits (Sütterlin and Siegrist 2017).
As the debate about the potential need for climate engineering becomes more intense, there is an increase in work exploring what predicts public support for specific types of strategy across both SRM and CDR. Corner et al. (2013) demonstrate how climate engineering evokes a complex set of ‘messing with nature’ narratives. In particular, people often view it as simply interfering with natural processes and ultimately not dealing with the main cause of climate change: anthropogenic carbon emissions. Wolske et al. (2019) have also explored the extent to which specific CDR strategies are perceived to be tampering with nature, finding greater support for afforestation and reforestation (AR) over BECCS and DAC (direct air capture), with AR perceived to mess with nature to a lesser extent. This effect was stronger in participants who were against human intervention in natural processes. This preference for AR is common, in part because it is perceived to be a more ‘natural’ approach as compared to other more technological strategies (Corner and Pidgeon 2015; Campbell-Arvai et al. 2017).
One common methodological consideration across much of this risk perceptions work is the need to provide study participants with information about each technique due to low levels of familiarity, which may include giving information about potential risks and/or benefits. Usually this information is made as neutral and balanced as possible to avoid framing effects. When awareness is low, however, information provision is likely to influence level of support as both perceived risks and benefits contribute to attitude formation, with those perceiving greater risks than benefits tending to be more opposed to new technologies (Slovic 2000). There is evidence that providing further information about both the risks and benefits of different climate engineering strategies, as opposed to merely providing a description of techniques, tends to result in reduced support (Braun et al. 2017; Wolske et al. 2019), and this has been attributed to how serious respondents perceived climate change to be, or alternatively the extent to which a particular strategy is thought to be tampering with nature. In the Braun et al. study, those who saw climate change as more serious were more accepting of measures but perceived the information more negatively than those who did not perceive climate change as a serious issue. Wolske et al. (2019) likewise found that after respondents had read further information about three CDR strategies, BECCS was seen as most likely to tamper with nature and therefore had reduced levels of support.
Another important component of risk perception is the role of affect: the positive or negative feeling instinctively associated with a risk issue or technology (Slovic et al. 2007). For example, Merk and Pönitzsch (2017) clearly showed that those who felt more positive about stratospheric aerosol injection (one type of SRM) had an increased benefit perception and decreased risk perception, and the reverse for those with negative affect. The affect heuristic allows people to evaluate novel technologies with limited to no knowledge about the topic. Sütterlin and Siegrist (2017) show that even with limited information, people evaluate SRM negatively, with this producing a stronger negative affective response in those given further information about possible risks. The authors surmise that people no longer only have their affective evaluation of climate change to rely on but can now utilise the information received about SRM, which means how technology is described will likely predict the relation between climate change concern and perceptions of climate engineering.
Public perceptions of enhanced terrestrial weathering
Most recent public perceptions literature has focussed on a range of climate engineering strategies, across both CDR and SRM, allowing for comparisons between specific strategies. However, there are very few survey studies that have included enhanced weathering, which is the key focus of this research. Wright et al. (2014) did include enhanced weathering in a survey investigating perceptions of six climate engineering strategies (three CDR and three SRM) in New Zealand and Australia. There were higher net positive associations made with the CDR strategies, all being judged as more controllable and sustainable than SRM. This was also true for enhanced weathering, although in this study it was not viewed as a very distinct concept by respondents: in other words, it did not produce particularly positive or negative associations when considered by people, in comparison to the other climate engineering strategies judged. Follow-up work included a further two countries (the UK and USA) replicating this finding, but also explored support for small-scale field trials (Carlisle et al. 2020). Results illustrated mixed support for trials with a similar pattern across all four countries consistent with earlier studies. CDR was more supported than SRM. Participants also displayed considerable ambivalence around supporting trials for all strategies, with many neither agreeing nor disagreeing that trials should occur, including in the case of enhanced weathering. Jobin and Siegrist (2020) also recently explored the key drivers of public support for 10 different climate engineering strategies (seven CDR and three SRM) finding highest support for afforestation and lowest support for SRM. Specific to enhanced weathering (alongside other soil-based CDR strategies), there were low levels of public knowledge. With regard to general support, higher perceived benefits increased support for use of enhanced weathering and higher perceived risks (and perceptions of tampering with nature) decreased support for deployment.
The studies to date provide an indication of how the public perceive different CDR strategies compared to each other, including the few studies described above incorporating enhanced weathering. However, building understanding of risk perceptions of any single CDR technology also requires investigating specific approaches in greater detail. This more targeted approach allows for greater provision of technology-specific information and survey questions and scales which are tailored to the technology under consideration. Accordingly, the present study examined perceptions towards enhanced weathering as one possible CDR strategy to help mitigate climate change, building on previous survey work with respondents from the UK (Pidgeon and Spence, 2017). This earlier work, utilising a limited range of technology specific items, confirmed that, as with other climate engineering approaches, enhanced weathering was unfamiliar to most respondents, while those who were more supportive of the approach also felt greater positive affect and perceived more benefits than risks of the approach.
The current cross-national study
To extend previous work, we surveyed the populations of three Westernised countries where small-scale field trials of the enhanced weathering techniques described previously are already occurring (the UK, the USA, and Australia). The survey examined what influences support for deployment of enhanced weathering and whether this differs between countries, and the extent to which support is related to people’s beliefs about climate change. All three countries have seen significant increases in climate concern in recent years. In Australia, following several extreme heat and wildfire seasons over recent summers, the percentage of respondents very concerned about climate change increased to 47% in January 2020 (TAI 2020), a percentage which has almost doubled since 2010 (Reser et al. 2012). In the UK, 40% expressed being ‘very’ or ‘extremely’ worried in late 2019, a figure which had doubled since 2016 (Steentjes et al. 2020). In the USA, there had likewise been an increase in those most worried about climate change with 31% in 2019 classified as ‘alarmed’, a segment of the US population that had tripled between 2014 and 2019 (Leiserowitz et al., 2020). Accordingly, this is the first study to explore public perceptions of enhanced weathering in detail across these three countries in light of increases in climate concern, and will help provide initial insights into how people rationalise their support for such a novel CO2 removal approach.
We hypothesised that people would be unfamiliar with enhanced weathering, as it is a novel approach to CO2 removal (Wright et al. 2014; Carlisle et al. 2020), while both positive affect and concern about climate change would be positively related to support for enhanced weathering (Pidgeon and Spence, 2017), and that those who perceived more benefits would also be more supportive (Merk and Pönitzsch 2017). We also included an option eliciting open-ended responses to help explain why people would or would not support development of enhanced weathering, as here we expected a high degree of ambivalence (Carlisle et al., 2020; Pidgeon and Spence, 2017).