Organic Solar Radiation Modification

[Geoengineering News]

https://tellusjournal.org/articles/10.16993/tellus.4133

Authors: Markku Kulmala, Anton Laakso, Mikael Ehn, Katrianne Lehtipalo, Veli-Matti Kerminen

10 April 2026

Abstract

Despite the urgency to mitigate climate change, global greenhouse gas concentrations are still increasing, and even global emissions are still growing. Furthermore, the global sinks—both natural and technical—are not improving rapidly enough. Therefore, discussion and investigations to utilize solar radiation modification (SRM) have resurfaced. Stratospheric Aerosol Injection (SAI) is one of the most studied methods, particularly using sulfate aerosols. However, sulfate SAI includes several risks, such as deposition of acidic aerosol particles on the Earth’s surface, increasing acidification and ozone depletion, and changing weather patterns. Here we propose an alternative approach, namely Organic Stratospheric Aerosol Injection (OSAI). The OSAI is initiated by an injection of isoprene or monoterpenes, which, according to our conceptual investigations and global model simulations, seem to be plausible candidates for this purpose. The organic SAI is likely to avoid some of the problems inherent to sulfate SAI, even though further research is needed in terms of its potential influences on stratospheric heating and the ozone layer. While SRM is still preferably avoided, our results suggest that organic aerosols may be an alternative to sulfate for further consideration if it is deemed a viable and necessary option.

Source: Tellus

[Renaud de RICHTER]

The authors did not mention the effects of the additional water generated in the stratosphere (VOCs → O₂ + H₂O). It appears they completely overlooked the chemistry of halogens in the stratosphere. For example, chlorine atoms (from anthropogenic CFC emissions and biogenic emissions of halogenated molecules) react nearly 100 times faster than OH radicals with VOCs, and their overall lifetime is therefore much shorter.

Short excerpt from the article:

The summary of the OSAI concept consists of the following steps (see also Figure 1):

1) A suitable organic vapor (e.g., isoprene/monoterpene/sesquiterpene) injected/transported to the lower stratosphere
2) Oxidation of the organic vapor by stratospheric O3 and OH to produce ELVOCs
3) Clustering of ELVOCs to form new aerosol particles (nucleation)
4) Growth of the initial ~1 nm particles to 300–600 nm (SOA formation)
5) Scattering of radiation back to space by the formed SOA particles

6) Further oxidation making more volatile compounds and evaporation of the particles. The end product is CO2, and the produced amount of CO2 is less than 0.1% of current global anthropogenic CO2 emissions.

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