Solar radiation management – risks from reversing climate change

Solar radiation management (SRM) is an umbrella term for approaches to reduce global warming by intentionally reflecting increasing amounts of incoming sunlight back to space. SRM does not impact the root-cause of global warming, namely greenhouse gas (GHG) emissions. Its utility is to lower temperatures. However, if implemented and then suddenly terminated, the result of SRM could be fast temperature increases, bringing on related weather effects.¹

SRM approaches include Cirrus Cloud Thinning (CCT), Ground-based Albedo Modification (GBAM), Marine Cloud Brightening (MCB) and space-based approaches involving placing mirrors, shades or reflecting particles in the space between the sun and the earth.

To date, one of the most-studied SRM options is the stratospheric aerosol injection (SAI). SAI is the intentional release of highly reflective fine particles or their precursors at an altitude of 20–25 km. The effect would be similar to the Mount Pinatubo eruption on 15 June 2001. The volcano threw about 15 million tons of sulphur dioxide into the stratosphere, where it reacted with water to form a hazy layer of aerosol particles. Strong stratospheric winds spread these aerosol particles around the globe. Over the next 15 months, the average global temperature dropped by about 0.60 °C.²

The risks and benefits of SRM ³

Unintended climate changes. SRM is essentially climate change in reverse: it cools the earth. Just as current temperature increases are likely fuelling changes in climate (drought, wet seasons) and extreme weather events (storms, flooding), so too will cooling via SRM. To predict the effects of cooling, new models are needed reflecting where, what cooling agent is used and how much, and for how long it is injected into the stratosphere.⁵ As models are currently under development, it is difficult to say which countries/regions would benefit or be harmed by consequent changes in climate and weather patterns. Any pattern changes, however, could lead to unanticipated losses for insurers.⁶ One example of this could be a shift in the geographical range of communicable diseases like malaria, which could redistribute in developing countries.⁷ It could also lead to an increase or geographical shift of extreme weather events like droughts or hurricanes.⁸ In general benefits and risks would most likely not be fairly distributed globally. Hence, the question is how to compensate those experiencing negative effects.

Potential disruption of ecosystem services.⁹ SRM could change many climate variables other than temperature that are important for ecological systems. These include key ecological drivers, such as the ratio of diffuse to direct radiation, ultraviolet (UV) radiation, the connection between temperature and CO₂, precipitation distribution, seasonality, acid precipitation, air quality and changes to surface ozone to name just a few. The resulting possible consequences of SRM implementation are wide ranging, from species decline and relocation, to populations stabilisation and even growth, changes to ecosystem processes and the emergence of novel ecological communities adapting to new climates. In turn, these could trigger agricultural losses, health problems (ozone and UV radiation) and migration, bringing also insurance losses.¹⁰

Potential for international conflict. Some countries may pursue climate engineering while others condemn the practice. This would likely see “winners and losers”: some nations would gain relative to a world without climate engineering, some would lose, and none would be unaffected.¹¹ The result could be cross-border conflicts, leading to economic contraction.

Societal risks. Considerable amounts of SRM must take place over a longer time,¹² and this requires substantial finances. It is possible that non-state actors will start SRM on their own, either because they see climate change as the ultimate threat or, conversely, as a business opportunity. One company is already trying to develop a business out of SRM. A first small-scale trial of a start-up to show a “proof of concept” to later sell cooling credits has already taken place.¹³ The cooling credits could be sold as offsets to GHG emitters.

Legal and regulatory risk. Solar geo-engineering proposes a regime of intentional, planetary climate modification. In theory this would require a planetary governance body, which does not currently exist. Instead, international law is decentralised, relying on state cooperation, obedience and internalisation of those rules for their enforcement.¹⁴ There are some international treaties ¹⁵ – most notably the Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD),¹⁶ – but none address the issue fully. Hence, it is not clear what kind of legal framework would apply in a case of insured losses due to SRM being disputed, be it between states, private entities or all these parties. Issues like this are already important to losses, as demonstrated in current cases of climate change litigation.¹⁷

Missing out on benefits of lowering GHG concentrations in the atmosphere. Cooling the earth via SRM may lower the earth’s temperature. But SRM does nothing to reduce GHG concentrations in the atmosphere.¹⁸

With acknowledgment of the very large costs associated with climate change, governments are looking into SRM to assess technical feasibility. Academic research is ongoing in Canada, India, Japan, Australia, Germany and the UK. The US is considering a five-year study into the technologies.¹⁹ Research programs in China are also modelling the climate effects.²⁰ Insurers should follow these developments carefully. Global warming can be expensive: the same could be true for man-made global cooling.