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The European Union, the United States and China are currently funding research to better understand controversial and speculative technologies called Solar Radiation Management (SRM) as a climate change mitigation strategy.
A new report from the United Nations Environment Program (UNEP) warned that deploying SRM comes with environmental and social risks, which could occur in at least the next seven years.
SRM or solar geoengineering involves using technologies to cool the earth by reflecting sunlight into space. One strategy mimics volcanic eruptions, which release aerosols to block solar radiation.
Following the June 1991 volcanic eruption of Mount Pinatubo in the Philippines, global mean air temperatures dropped by up to 0.5 degree Celsius at the surface and 0.6°C in the troposphere, for some months in mid-1992. Other technologies involved whitening clouds or deploying sunshades in space to increase Earth’s reflectivity.
Some 24 per cent of experts believe that disruptions due to SRM are “very likely” to occur and another 29 per cent voted that this could 'likely' occur, according to the UNEP report, Navigating New Horizons -- A Global Foresight Report on Planetary Health and Human Wellbeing.
If SRM is deployed, the intensity of impact could be negative, with experts providing it a score of 2.1 on a scale of 1-3, where 1 is low and 3 is high.
SRM was ranked 16 on a perception score, which is determined by comparing it with 17 other potential signals of change like artificial intelligence and emerging zoonotic diseases.
The report is based on nearly 1,200 responses submitted by 790 respondents to a survey conducted in May 2023. This exercise identified 280 specific signals of change.
The Foresight Expert Panel – comprising 22 distinguished members of the scientific community from developing and industrialised countries – further shortlisted the signals.
“Today, with climate impacts rising and becoming more severe and frequent, concerns over the apparent inability to drastically cut emissions and scale up carbon dioxide removal are driving scientific research, investments, and development, as well as political and public interest, on the topic of SRM,” read the report.
Some of the concerns around SRM include potential extreme events, acid rain and altered precipitation patterns.
The other risk is termination shock, which is a rapid and substantial rise in global temperatures, after the technology is suddenly paused.
Other impacts and unintended environmental consequences include a delay in the closing of the ozone hole, warming of polar regions and cooling of the tropics.
Then there are concerns over what this could mean for geopolitics as experts fear it could lead to security risks. It could help developed countries at the expense of developing ones, which are already in distress due to changes to the environment and climate.
One of the biggest criticisms is that these technologies do not solve the underlying causes of climate change.
Currently, the UNEP report stresses that SRM technologies remain speculative and highly contentious, calling for scientific scrutiny and more inclusive public discourse on the implications of SRM.
“Choosing to ignore SRM altogether at this stage, could carry its own risks— leaving society and decision-makers ill-prepared and potentially misguided,” it read.
In 2023, a group of scientists advocated for an International Non-Use Agreement on Solar Geoengineering, targeting the development and deployment of such technology. They called for banning outdoor experiments and urged governments to prohibit funding.
The scientists cited several reasons, including that the risks of solar geoengineering are poorly understood, that these technologies threaten commitments to act against climate change and that the current global governance system is unfit to maintain fair, inclusive and effective political control over solar geoengineering deployment.