Governments have previously sought to reduce climate-change inducing concentrations of carbon dioxide (CO2) in the earth’s atmosphere through mitigation and adaptation activities, but are now exploring other measures. Negative emissions technologies (NET) are aimed carbon dioxide removal (CDR) to a level consistent with a desired temperature, while solar geoengineering, also known as solar radiation management, or modification (SRM) seeks to reflect sunlight away from earth and thereby reduce global temperatures. Existing measures to combat rising emissions have not been entirely successful, and CDR and SRM have consequently gained increased policy traction in recent years. Emerging technologies include bioenergy, carbon capture and storage (BECCS) and stratospheric aerosol injection (SAI). A careful, unbiased, and knowledge-driven assessment of the risks of these technologies is required, and that robust governance systems should be put in place before they are implemented any further.

CDR was investigated in an IPCC special report in 2005. The technology was acknowledged as one of the options for removing CO2 from the atmosphere arising from the combustion of fossil fuels for energy production and the burning of forests. Solar geoengineering has emerged as a supplement to CDR as a consequence of concerns that global GHG emissions are still increasing, and may result in an increase to 1.5 degrees warming as early as 2030, which partly explains the growing interest in more radical technologies to reduce risks of climate change.

BECCS was originally envisioned only as a backstop under an extreme climate scenario should ambitious emissions reductions prove unfeasible, in the context of commensurate broad-scale forest restoration and replanting, and as a risk management option. Nonetheless the technology has gained traction because of a loophole under the Kyoto Protocol which exempted forest loss from being counted as an emission, under the accounting logic that if the cleared area regrows, or is converted to another land-use (such as agricultural crops) it continues to take up carbon. The problem with the implementation of the technology is that initial modelling and pilot projects assumed fuels would come mostly from energy crops and that if residues were used, they would all have similar emissions profiles. In reality, wood pellets are the most common energy source, and are not made from residues, but trees, with a measurably larger, and longer-term net emissions impact (NEI) than other sources. Countries have developed renewable energy policies on the basis of these prior assumptions, as was the case in the UK in 2015, where the government committed over £800 million in subsidies to biomass energy, while phasing out support for offshore wind power, and extending the life of coal-fired power stations using forests in their energy-mix, and net emissions are replacing zero emissions as a policy outcome

SRM, is a set of emerging technologies aimed at altering the Earth’s radiative balance, reducing the amount of climate change caused by greenhouse gases. Space-based techniques and stratospheric aerosol scattering have the potential to block or reflect a small portion of incoming sunlight, cooling the planet and thus reducing the risks of climate change. The leading suggested method is to mimic volcanic activity, whereby fine dust naturally lowers global temperatures for a year or two after large eruptions such as Mount Pinatubo in 1991. Another method involves spraying seawater upwards as fine droplets, which could brighten low-lying marine clouds, thereby reflecting more sunlight. This particular technology has been identified as the source for a range of popular conspiracy theories, including the belief that world governments were filling the atmosphere with toxic pollutants (‘chemtrails’). Although the injection of aerosols into the atmosphere might reduce heat stress on agricultural crops, the resulting reduction in sunlight could have other less positive impacts. Models replicating the impacts of sulfur in the atmosphere from volcanic eruptions, on which this technology are based, indicate the apparent benefits of planetary cooling are outweighed by a reduction in crop yields, while the effects on ecosystem function and human health are unknown.

Despite, or indeed, because of, the IPCC’s previous recognition of the need to give consideration to such technologies, it must continue be emphasized that the most effective approach to reducing climate change risks remains the prevention of greenhouse gas emissions in the first place, and where this is not possible, the reliable, safe and environmentally benign removal of CO2 from the atmosphere. In the case of BECCS there are issues of scale; with the appropriate feedstock and the correct energy mix of wind, solar and bioenergy, there are few adverse impacts. But if scaling up results in the destruction of the world’s remaining primary forests, or taking away land for agricultural production, scale becomes critical and the technology unfeasible. SRM might not only affect the radiation balance but atmospheric chemistry and rain patterns as well. In addition, such techniques do not address the root causes of climate change and other negative effects of high atmospheric CO2 concentrations would persist, including ocean acidification and changes to ecosystems. In other words, business as usual could continue, including the combustion of fossil fuels, while reducing some of the impacts of solar radiation through such techno-fixes, and if solar radiation management should cease as a result of economic or political crises, the result would be a rapid increase in global temperatures, as the GHGs would still be in the atmosphere.

It is the nation-states that will ultimately have to address risks posed by climate change — for good or ill. Global collaboration is key to speeding up efforts to address climate change risks; failure in co-operation, notably between the main emitting countries such as US and China, will quickly translate into a significant increase of climate change, and many more people will have to suffer than are already affected. The dangers inherent in emerging technologies are not always clear, but appropriate responses to the challenges of climate change depend very much on the careful consideration and effective implementation of any additional measures identified by the scientific community as necessary. In order to conserve human society and biodiversity, an unbiased and knowledge-driven assessment of the risks posed by engineering the climate, as well as robust governance systems, are required.

Lastly, no examination of emerging technologies for CDR and SRM is complete without recognising the risks that accompany the mitigation of, and adaptation to, climate change. These have their own inherent problems, notably around the use of market mechanisms, and other approaches that are being negotiated under the Paris Agreement. To ignore the existing tensions in the climate change debate by turning to geoengineering as a panacea could make the current climate emergency even worse.

For a full version, including references, see: Radunsky, K., & Cadman, T. (2019). Governing the Sun, The International Journal of Social Quality, 9(2), 19-34, which, due to the corona virus outbreak, is currently open source:


Tim Cadman, Research Fellow, [email protected]

Klaus Radunsky, Chair, ISO TC207 SC7 Mirror Committee, Austrian Standardization Institute (ASI)