Solar Radiation Modification (SRM) technologies—such as Stratospheric Aerosol Injection (SAI) and Marine Cloud Brightening (MCB) are speculative concepts that aim to temporarily lower global temperatures by reflecting solar radiation back into space. These approaches do not reduce greenhouse gas concentrations—the root cause of climate change—nor do they address its impacts. These technologies also represent different levels of readiness and have been subject to a great deal of political and scientific controversy. Sometimes cast as an emergency tool, SRM remains poorly understood and fraught with uncertainties and risks and is no substitute for mitigation or stronger adaptation. For now, SRM is largely confined to models, simulations and theory. The unintended consequences include disruptions to climate patterns, biodiversity and the ozone layer, with regional hydrological impacts modelled as being uneven.
This Issues Note provides a review of the latest literature on specific topics that are of relevance to UNEP’s mandate. It also presents a set of agreed approaches and recommendations regarding UNEP’s communication of the subject matter. It is meant to ensure consistency in messaging across the organization on this topic.
