“The Earth, a Planet like no Other” – Online Presentation with Anny Cazenave

This presentation was recorded on November 13, 2020 (on the occasion of ISSI’s 25th anniversary).

Abstract: The Earth is the only planet of the Solar System hosting evolved life. «How to build an habitable planet ?» has led to considerable scientific literature in the recent decades and has strongly motivated research on exoplanets. All along its history the Earth has displayed specific chemical and physical properties, including a relatively stable climate that a played major role in the evolution of living organisms. In this presentation we discuss the physical particularities of planet Earth, such as gravity and magnetic fields, rotation, mantle convection and plate tectonics, volcanism and water cycle, and their impacts on climates and life, from paleo times to present. Today, Homo Sapiens polulation is approaching 8 billions, a factor 8 times larger than 2 centuries ago, and an indirect consequence of fossil energy use and associated technological innovation. However, our present-day world is facing a number of new «Grand Challenges», as summarized by the United Nations (UN) 2030 Agenda for Sustainable Development. By providing invaluable information on the Earth system and its evolution under natural and anthropogenic forcing factors, Earth observation from space has a key role to play for reaching several of the 17 Sustainable Development Goals of the UN 2030 Agenda, in particular those related to current climate change, water resources, land and marine biodiversity and food security.

Anny Cazenave received her Ph.D. in geophysics in 1975 from the University of Toulouse. Subsequently, working at the French space agency CNES, she went into space geodesy, the use of satellites to track changes in Earth’s surface, gravity field and orientation in space. She first focused on the dynamics of the oceanic crust and the mechanically strong layer of the uppermost mantle below it. Among other things, she used early space- borne radars to show that the ocean surface is not flat, but follows the topography of the ocean floor. In other early work, she addressed questions about the rotation of Venus and the origins of the Mars moons, Phobos and Deimos. Towards the end of last century, European and American space agencies launched a new series of satellite radar altimeters capable of monitoring sea level everywhere in the world oceans in more or less real time. By the early part of the 21st century, it had been determined that global sea level was rising by at least about three millimetres a year. As one of the leading scientists in the joint French/American satellite altimetry missions, TOPEX/Poseidon, Jason-1, and the Ocean Surface Topography Mission, Anny Cazenave has contributed to a greater understanding of this sea level rise and its dependence on global warming. Besides a large number of publications, Anny was lead author of the sea level sections of the Intergovernmental Panel on Climate Change’s most recent full reports, in 2007 and 2014.

Since 2013, she has been director of Earth sciences at the International Space Science Institute in Bern. In 2020, she received the prestigious Vetlesen Prize, often referred to as the Nobel Prize in geophysics, for her pioneering work in using satellite data to chart and quantify rises in the surface of the oceans, and related changes in ice sheets, landmasses and freshwater bodies.