Imagine a giant dimmer switch for the planet — an emergency brake on global warming. Solar Radiation Management is a bold and controversial idea that aims to reflect a small fraction of sunlight back into space to cool the Earth. One leading approach involves injecting tiny aerosols into the upper atmosphere, mimicking the cooling effect of volcanic eruptions and enhancing the brightness of clouds. Could this be a powerful tool to buy time in the climate crisis? Or are we opening a Pandora’s box with unpredictable consequences?

Aerosol Research: A Key Discipline in Potential Geoengineering

Atmospheric and aerosol scientists are increasingly discussing the technical challenges and potential environmental impacts of such geoengineering approaches. This “cloud brightening” is often connected to artificially elevated levels of cloud condensation nuclei — small aerosol particles with diameters well below 1 μm (around 100 times smaller than a human hair). These particles are often formed when gaseous molecules cluster into small particles in the atmosphere.

At the 22^nd International Conference on Nucleation and Atmospheric Aerosols (ICNAA), opens an external URL in a new window, held in Vienna from August 24 to 28, 2025, international researchers from five continents will come together to discuss the latest scientific advances in aerosol formation and its role in cloud and ice cloud formation. The conference is jointly organized by research groups from the University of Vienna, opens an external URL in a new window and TU Wien — both leading institutions in these fields.

Geoengineering Goes Beyond the Technical Sciences: Time for Discussion

But the technical side is only one part of the picture: these ideas and the associated research must also be considered from broader perspectives, including geopolitics and the complex relationship between science and policy-making. Such a dramatic human intervention in the Earth system would be unprecedented. As an intentional countermeasure, it would differ fundamentally from previous unintentional interferences, such as anthropogenic CO₂ emissions or the destruction of the ozone layer by CFCs.

Therefore, Solar Radiation Management requires a broad public debate — not only about whether we should pursue it, but also about the implications if other global actors were to implement it without international consensus.

Public panel discussion: Experts from Politics, Sociology, and Natural Sciences Come Together

We invite you to attend a public panel discussion at Palais Eschenbach on August 27 at 7:00 PM, focusing on aerosol science and geoengineering. Prof. Markku Kulmala from the University of Helsinki — one of the most cited geoscientists in the world — will give an introductory talk on how small-scale processes are linked to global grand challenges.

This will be followed by a panel discussion, supported by the Environmental and Climate Research Hub (ECH) and the Vienna Science and Technology Fund (WWTF). The discussion will be moderated by Raffael Himmelsbach from the Ludwig Boltzmann Gesellschaft, who has extensive experience in policy analysis, science governance, and public engagement.

The panel consists of both conference participants and external experts: Prof. Ulrike Felt (University of Vienna), who brings perspectives from the sociology of science, focusing on innovations and the societal traces they leave behind; Simon Ellmauer-Klambauer, Head of the Department of General Climate Policy of the Republic of Austria, who will highlight the political dimensions of the topic; and two experts in the field of geoengineering, Dr. Blazs Gasparini, Senior Scientist at the University of Vienna, and Prof. Zoran Ristovski (Queensland University of Technology), who will complement the panel and be available to answer questions from the audience.

Do we need to darken the sun? 
27 August 2025, 7 p.m.
Palais Eschenbach
Eschenbachgasse 11, 1010 Vienna
Please register in advance: icnaa2025@univie.ac.at