François-Marie BréonAvenir Commun Durable (2024-2025)Collège de FranceAnnée 2024-2025Colloque - Regards croisés sur la géo-ingénierie : Évaluation de la géo-ingénierie à l'Académie des sciencesFrancis AlbarèdeGéologue et géochimiste, professeur émérite, membre de l'Académie des sciencesRésuméThis presentation explores geoengineering – a set of ideas aimed at cooling the planet if cutting greenhouse gas emissions isn't enough to stop climate change. It looks at two main strategies: Solar Radiation Management (SRM) and Carbon Dioxide Removal (CDR).SRM methods try to reflect more sunlight away from the Earth. These include techniques like injecting particles into the upper atmosphere, making clouds more reflective, or thinning certain types of clouds. While these could cool the planet, they also come with risks, such as changing rainfall patterns or affecting the ozone layer.CDR approaches focus on removing carbon dioxide (CO₂) from the atmosphere. This might involve planting coastal vegetation, spreading crushed rock on land, or making the oceans more alkaline so they absorb more CO₂.The presentation makes it clear that geoengineering is not a substitute for cutting emissions, but something to consider if those cuts fall short. These technologies raise big scientific and ethical questions, and this talk aims to provide a framework for understanding them and starting a public conversation about their future use.Francis AlbarèdeFrancis Albarède is a French geochemist internationally recognized for his work in isotope geochemistry and the application of mass spectrometry to Earth sciences.He has made major contributions to understanding the origin and differentiation of the Earth's mantle and crust, the cycling of elements in oceans, and the formation of ore deposits. In the 1990s, he played a pivotal role in advancing high-precision isotope analysis by acquiring one of the first commercial multi-collector inductively coupled plasma mass spectrometers (MC-ICP-MS), a technology that revolutionized the field.Albarède's research spans geochemistry, volcanology, paleoclimatology, and planetary science, with studies ranging from the isotopic signatures of ancient oceans to the composition of Martian meteorites. He is also known for integrating quantitative models with geochemical observations, applying a physicist's precision to Earth science problems. His interdisciplinary work, notably on metal isotopes in medicine and archaeology, has gained wide recognition.He is currently professor emeritus at the École Normale Supérieure de Lyon and a visiting scientist at Rice University. Among many distinctions, he has been elected to the Académie des sciences and awarded the Nemmers Prize in Earth Sciences and the V.M. Goldschmidt Award.

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