“The Contemporary Global Carbon Cycle and the Impact of the COVID-19 Pandemic on CO2 Emissions” with Corinne Le Quéré  (University of East Anglia, UK)


Emissions of carbon dioxide (CO2) from human activities have caused the planet to warm and have set in motion a train of changes in the natural carbon cycle. Every year, the land and ocean natural carbon reservoirs, the so-called carbon ‘sinks’, absorb 55% on average of the CO2 emissions we put in the atmosphere from burning fossil fuels, deforestation, and other activities. The carbon sinks slow down the pace of climate change, but they respond themselves to a changing climate by leaving more CO2 in the atmosphere. The latest evidence on trends in emissions and sinks of carbon of the past 60 years reveals the limits of our understanding and the challenges we face to develop a planetary monitoring system that can keep track of the rapidly changing carbon cycle. The Covid-19 pandemic generated the need to monitor global emissions daily, something that was thought impossible before. From this need has arisen an explosion of new research methods on monitoring the carbon cycle. This presentation will provide a snapshot of current understanding and capacity to untangle changes in the Earth’s vital organic element: carbon.

Corinne Le Quéré is Royal Society Research Professor of climate change science at the University of East Anglia. She conducts research on the interactions between climate change and the carbon cycle. Her research has shown that climate change and variability affects the capacity of the Earth’s natural carbon reservoirs to take up carbon dioxide emitted to the atmosphere by human activities. Corinne Le Quéré instigated and led for 13 years the annual update of the global carbon budget, an international effort to inform global climate agreements. She was author of three assessments reports by the Intergovernmental Panel on Climate Change, which was awarded the Nobel price prize in 2007, and is former Director of the Tyndall Centre for Climate Change Research. Professor Le Quéré is Chair of France’s High Council on climate, an independent experts body that advises the French Government on its responses to climate change, and member of the UK Committee on Climate Change. She was elected Fellow of the UK Royal Society in 2016 and was appointed Commander of the Order of the British Empire (CBE) in 2019 for services to climate change science.

This webinar was recorded on July 22, 2021

“Testing the Massive Black Hole Paradigm with High Resolution Astronomy” with Reinhard Genzel (Max Planck Institute for Extraterrestrial Physics, Garching, Germany)

The discovery of the Quasars in the 1960s led to the ‘massive black hole paradigm’ in which most galaxies host massive black holes of masses between millions to billions of solar masses at their nuclei, which can become active galactic nuclei and quasars when they accrete gas and stars rapidly. I will discuss the major progress that has happened in the last decades to prove the massive black hole paradigm through ever more detailed, high resolution observations, in the center of our own Galaxy, as well as in external galaxies and even in distant quasars. In the Galactic Center such high resolution observations can also be used to test General Relativity in the regime of large masses and curvatures.
Reinhard Genzel is an infrared- and submillimetre astronomer. He and his group are also engaged in developing ground- and space-based instruments for astronomical observations. They use these to track the motions of stars at the centre of the Milky Way around Sagittarius A*, and showed that these stars are orbiting a very massive object, now known to be a black hole. Genzel and his group are also active in studies of the formation and evolution of galaxies and active galactic nuclei. Reinhard Genzel was awarded the 2020 Nobel Prize in Physics (jointly with Andrea Ghez and Roger Penrose) “for the discovery of a supermassive compact object at the centre of our galaxy”.
Genzel had studied at Freiburg University and Bonn University, finishing his PhD in 1978 at the Max Planck Institute for Radio Astronomy in Bonn. As a postdoc he worked at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts; he was a Miller Fellow, then Associate Professor and in 1981 he became Full Professor in the Department of Physics at the University of California, Berkeley. In 1986, Genzel became director at the Max Planck Institute for Extraterrestrial Physics in Garching (near Munich) and in 1988 also Honorary Professor at Ludwig-Maximilians-Universität München. From 1999 to 2016, he had a joint appointment as Full Professor at the University of California, Berkeley, where he is now emeritus professor. Prior to the Nobel prize, Reinhard Genzel had received numerous awards, among them the Herschel Medal of the Royal Astronomical Society (2016), the Tycho Brahe Prize of the European Astronomical Society (2012) and the Karl Schwarzschild Medal of Astronomische Gesellschaft (2011).

This webinar was recorded on July 15, 2021

“(Almost) 50 Years of Coronal Heating” with Joan Schmelz (USRA, USA)

The actual source of coronal heating may be one of the longest standing unsolved mysteries in all of astrophysics, but it is only in recent years that observations have begun making significant contributions. Coronal loops, their structure and sub-structure, their temperature and density details, and their evolution with time, may hold the key to solving this mystery. A loop had always been thought of as a simple magnetic flux tube, where each position along the loop is characterized by a single temperature and density. Recent results, however, including loops with unexpectedly high densities, ultra-long lifetimes, and multithermal cross-field temperatures, were not consistent with results expected from steady uniform heating models. A loop, however, may be a tangle of magnetic strands, like the structures revealed by the High-resolution Coronal Imager. Hi-C observed magnetic braids untwisting and reconnecting, dispersing enough energy to heat the surrounding plasma. The hot (T > 5 MK) plasma observed in most active regions also provides a key observation. The existence of multithermal, cooling loops and hot active region plasma do not yet prove that one particular mechanism heats the corona, but these results do provide observational constraints that all viable coronal heating models will need to explain.

Joan Schmelz is the director of the NASA Postdoctoral Program at Universities Space Research Association (USRA). She was the Associate Director for Science and Public Outreach at SOFIA, the Stratospheric Observatory for Infrared Astronomy (2018-19), and the deputy director of the Arecibo Observatory in Puerto Rico (2015-18). She was a program officer for the National Science Foundation’s Division of Astronomical Sciences (2013-15) and a professor at University of Memphis for over 20 years. Her research involves observations of solar coronal loops and developing constraints for coronal heating models. Schmelz has published papers on a variety of astronomical topics including magnetic fields, gas dynamics, and physical properties in stars, galaxies, interstellar matter, and the Sun using data from ground- and space-based telescopes at (almost) every band of the spectrum. She is the chair of USRA’s Diversity, Equity, and Inclusion Committee, a former Vice President of the American Astronomical Society, and a former chair of the Committee on the Status of Women in Astronomy. She won a teaching award from Rensselaer Polytechnic Institute, a service award from Gallaudet University, and a research award from the University of Memphis. She gives talks and writes articles on topics such as unconscious bias, stereotype threat, and the gender gap. She was honored in 2015 as one of Nature’s top ten people who made a difference in science for her work fighting sexual harassment.

This webinar was recorded on July 8, 2021


“Age and Formation of the Moon” with Thorsten Kleine (Münster University, Germany)

The Moon has been Earth’s steady companion ever since about 4.4 billion years ago. The age of the Moon and just how it formed is still a matter of intense scientific debate and research. Soon after the return of the first Apollo lunar samples, early hypotheses of the formation of the Moon (co-accretion, fission, and capture) have mostly been discarded in favor of the giant impact model, whereby a collision between a Mars-sized body with proto-Earth led to vaporization of the outer rock layers, expansion of the vapor cloud, and, ultimately, cooling and accretion of a comparatively iron-poor planetary body in orbit around Earth. Geophysical evidence for a small iron core and petrological evidence for an early lunar magma ocean lend credibility to the hypotheses. The giant impact model also predicts that the Moon consists predominantly of impactor mantle material. This implies that the Moon should be isotopically distinct from Earth, but isotope data for lunar samples have convincingly shown that it is not. This “lunar isotopic crisis” has led to the development of a new generation of giant impact models, in which the Moon either formed mostly from Earth’s mantle or isotopically equilibrated with the Earth after the giant impact. However, whether or not these models can account for the high degree of isotopic homogeneity of the Earth and Moon remains a matter of debate. 

The analyses of lunar samples not only provide clues to how but also when the Moon formed. Although the giant impact cannot be dated directly, the age of the Moon can be determined by dating the solidification of the lunar magma ocean. Yet, there is debate about how the ages of the distinct crystallization products of the magma ocean can be tied to the age of the Moon. The most recent results provide a Moon formation age of 4.425 ± 0.025 billion years, which is remarkably similar to the combined hafnium-tungsten and uranium-lead age for core formation on Earth. This suggests that the Moon-forming impact triggered the last major core formation event on Earth, as predicted in the giant impact model. 

Thorsten Kleine is a professor for Planetology at the University of Münster, Germany. He is a member of the North-Rhine Westphalian Academy of Sciences, Humanities and Arts, a fellow of the Meteoritical Society, recipient of the F.W. Clarke Award of the Geochemical Society, of the Victor Moritz Goldschmidt Award of the German Mineralogical Society, and of the Nier Prize of the Meteoritical Society. Thorsten Kleine specializes in isotopic studies of meteorites, lunar, martian and terrestrial rocks. His work is highly cited and is supported by an ERC Consolidator Grant. Since 2020 he is speaker of the DFG-funded collaborative research center “Late Accretion onto the Terrestrial Planets”, which investigates the late growth history of the Earth and Moon.

This webinar was recorded on July 1, 2021

“Weather Disasters in a Changing Climate” with Stephen Belcher (MET Office, Exeter, UK)

Weather and climate extremes such as heatwaves, heavy rainfall, drought, wind storms, flooding and wildfires have huge socio-economic and environmental costs. And climate change is already driving changes in weather extremes. Since the Paris Agreement in December 2015 there is a focus on the transition to net zero emissions, in order to limit the damage from climate change. Nevertheless, we are committed to further changes on the climate system, and so there remains a need to understand the impacts of further changes to the climate and to build resilience. As a result, the focus of climate science research at centres such as the Met Office has shifted to reflect these changing drivers: moving from proving that climate change is happening, to understanding the nature of the change and helping design solutions. This presentation will survey some of the inspirational new work that is being done to rise to this enormous challenge, including new observations, new modelling for projections, and new partnerships that are needed to move to building solutions.

Stephen Belcher obtained his PhD in fluid dynamics from the University of Cambridge (UK) in 1990 and has subsequently published over 100 peer-reviewed papers on the fluid dynamics of atmospheric and oceanic turbulence. Having completed his PhD he became a research fellow at Stanford and Cambridge Universities. In 1994 he moved to the Department of Meteorology at the University of Reading (UK), where he served as Head of the School of Mathematical and Physical Sciences between 2007 and 2010.  In 2010 he became the Joint Met Office Chair in Weather Systems. This role gave him a taster of working closely with the Met Office, and in 2012 he joined the Met Office as Director of the Met Office Hadley Centre (UK).Stephen led the evolution of the Met Office Hadley Centre to focus on climate science and services: motivated by the need to provide governments, industry and society with actionable advice, i.e. ‘climate services’. He was a driving force behind the initiation of the Newton Fund Climate Science for Service Partnership China (CSSP China), in which scientists from both China and the UK are now working together to develop fundamental climate science and climate services.

This webinar was recorded on June 24, 2021

“Do We Know What the Sun is Made of? The Puzzle of the Solar Composition” with Sarbani Basu (Yale University, USA)

All stars, including the Sun, are predominantly made of hydrogen and helium. However, the very small amount of the remaining elements, or “metals” as they are called, has a profound effect on the structure and evolution of a star. This is mainly because metals impede radiation – the higher the metallicity, the more opaque stellar material is. Given the proximity and ease of observing the Sun, solar metallicity is used as the reference for the metallicity of other stars. However, for the last two decades, there is no consensus about what the solar metallicity is.

In the early 2000s, the solar composition was revised downwards by about 30%, a result of analyses using 3D atmospheric models and non-LTE effects. While under most circumstances, this result would have been hailed as a triumph of using the best physics to analyze spectra, it created a problem – solar models constructed with the older metallicities matched the structure of the Sun, the models with the newer metallicities are extremely discrepant.

The structure of the Sun can be determined in a model-independent manner by analyzing the frequencies with which the Sun oscillates. All such analyses have shown that the lower abundances produce models that are discrepant. Although the metallicity estimates have increased since the original low ones, they are not high enough to result in solar models whose structures agree with that of the Sun.

In this talk, the speaker will review the problem and discuss how helioseismology, i.e., the study of solar oscillations, can be used to examine solar metallicity. She will also discuss attempts that have been made to change, as well as test, inputs to solar models in an attempt to reconcile the low abundances with helioseismic results. The speaker will end by discussing how solar neutrinos might provide the answer to the question of what the Sun is made of.

Sarbani Basu is the William K. Lanman Jr. Professor and Chair of the Department of Astronomy, Yale University. She is a global authority in helioseismology, or the study of the structure and dynamics of the sun using solar oscillations, her research also uses the sun as a laboratory to study the physics within it. She received the George Ellery Hale Prize of the American Astronomical Society in 2018 for her contributions to the understanding of the internal structure and dynamics of the Sun and stars. She served as the Chair for the panel on Starts, the Sun and Stellar Populations for the Astro2020 decadal survey; the survey will determine the direction of US astrophysics for the next decade.

This webinar was recorded on June 17, 2021

“The Merger History of the Milky Way – What Gaia Revealed” with Eva Grebel (ZAH, Heidelberg University, Germany)

The ESA Cornerstone Mission Gaia is revolutionizing our understanding of the assembly history of the Milky Way. Cosmological models suggest that Milky Way-like galaxies are made up in part of stars that formed in situ and in part of stars that formed in other, smaller galaxies and that were subsequently accreted. Most of the more massive merger events should have occurred more than nine or ten billion years ago. Such galactic cannibalism is believed to be the typical mode of growth of more massive galaxies. The surviving satellite galaxies, which all host ancient stellar populations, hold important clues to the properties of those early building blocks.

In combination with massive ground-based photometric and spectroscopic surveys, Gaia is confirming and refining the cosmological picture. Gaia data have uncovered numerous stellar tidal streams in our Galaxy, not all of which have known progenitors. Many come from disrupted dwarf galaxies, others from dissolving globular clusters – Gaia permits us to trace the detailed assembly history of our Galaxy, revealing the type of objects, their numbers, their properties, and the time of accretion. The most spectacular discovery is arguably that of the fairly massive dwarf galaxy Gaia-Enceladus or Gaia Sausage, which merged with the Milky Way about 10 Gyr ago. This event contributed many globular clusters and likely triggered the formation of the thick disk. In fact, Gaia data suggest that possibly half of our globular clusters come from merger events. Also, Gaia reveals the orbits of the surviving satellites, providing clues to their origins and future merger history.

Eva Grebel is professor of astronomy at Heidelberg University and director of the “Astronomisches Rechen-Institut”. She leads a collaborative research center (Sonderforschungsbereich) on the Milky Way system funded by the German Research Foundation (DFG).  She is a member of the Heidelberg Academy of Sciences, of the Hector Fellow Academy, and of the German National Academy of Sciences (Leopoldina).  For her work on galactic archaeology, she has received a number of scientific awards. A more detailed CV of Prof. Grebel can be found at https://wwwstaff.ari.uni-heidelberg.de/mitarbeiter/grebel/CV.html

This webinar was recorded on June 10, 2021

“Planet Formation and Evolution: Key Processes to Understand the Diversity of Planetary Systems” with Alessandro Morbidelli (Observatoire de la Cote d’Azur, Nice, France)

Prior to the detection of an ever-increasing multitude of exoplanetary systems, the solar system was held to be the proto-type of a planetary system. But the discovery of a large number of extrasolar planets has demonstrated that our own system is not “typical”. Exo-planetary systems can be very different from our own, and diverse from each other. Admittedly, there is an observational bias towards the detection of exoplanetary systems with close-in large planets, but the available data suggest that a real majority of systems are fundamentally different from our own. Understanding this diversity is a major goal of modern planetary science. The formation of planetary systems is not fully understood, but major advances have been obtained in the last 10 years. New concepts have been proposed, such as the streaming instability for the formation of planetesimals and pebble accretion for the formation of protoplanets. It is also now clear that planets forming in the proto-planetary disks have to migrate during theiraccretion, if their mass exceeds a few times the mass of Mars. Accretion and dynamical evolution are therefore very coupled processes. This leads to complex evolutions, very sensitive to initial conditions and fortuitous events, that are the key to understand the observed diversity of planetary systems. The early formation of Jupiter and its limited migration due to the formation of Saturn are two fundamental ingredients that determined the basic structure of the Solar System. The lack of early formation of giant planets typically leads to the formation of super-Earth planets on short period orbits. There is also evidence that the vast majority of planetary systems become unstable after the removal of the protoplanetary disk. The effects of this instabilityare very different depending on the masses of the planets involved. Our Solar System also experienced a global instability, but fortuitously our giant planets did not develop large orbital eccentricities.


Alessandro Morbidelli is a researcher in astronomy at the Observatoire de la Côte d’Azur in Nice, France. He is an Associate member of the French Academy of Science and of the Royal Academy of Belgium.  He specializes in celestial mechanics, the theory of Hamiltonian systems and the formation of planetary systems. He received the Prix Janssen of the Société Astronomique de France in 2018 and the CNRS silver medal in 2019. 

This webinar was recorded on June 3, 2021

“Terrestrial Planetary Seismology” with Philippe Lognonné (Institut de Physique du Globe de Paris, France)

Seismology is the ultimate tool for exploring the interior of planets but is technically extremely challenging as it requires the careful installation of highly sensitive sensors in an environment that is not always supportive. On the Earth, a large number of seismic stations and arrays has made a detailed tomographic mapping of the interior possible that even allows the imaging of the deep driving elements of surface plate tectonics and the detailed topography of e.g., the core mantle boundary. An array offour seismic stations has been operating for almost a decade on the lunar surface until it was shut off in 1977 and provided a wealth of data that is being studied even today by planetary seismologists. In 2018, the NASA InSight mission brought a highly sophisticated seismometer to Mars with three very broad band sensors and three sensors optimized short period signals. Because InSight is a single station – three stations are conventionally needed to locate a quake with travel times only – planetary seismologists adopted their inventory of interpreting tools to extensively use the data and compensate for the lack of additional stations. The method uses the individual runtimes of compressional, shear and, if detected, surface waves all generated by the same quake. Almost continuous monitoring of the seismic activity of Mars has confirmed that the planet is intermediate in activity between the larger Earth and the smaller Moon. The interpretation of the data has allowed to provide a layering in the crust underneath the landing site and is now constraining deeper structures, including the temperature profile in the mantle and core. The talk will be concluded on the future perspectives of planetary seismology in term of new mission toward the Moon, icy satellites and other terrestrial planets including Venus and Mars.


Philippe Lognonné is professor of planetary geophysics at the Université de Paris and perform his research in the Institut de physique du globe de Paris. He is a senior honorary member of the Institut Universitaire de France and a fellow of the American Geophysical Union. He is the instrument Principal Investigator of the SEIS experiment on the NASA InSight mission to Mars.


This webinar was recorded on May 27, 2021

“The Hubble Constant Controversy” with Adam Riess (Johns Hopkins University, USA)

The Hubble constant remains one of the most important parameters in the cosmological model which can be used to probe the nature of dark energy, the properties of neutrinos and the scale of departures from flat geometry.  By steadily improving the precision and accuracy of the Hubble constant, we now see evidence for significant deviations from the standard model, referred to as LambdaCDM, and thus the exciting chance, if true, of discovering new fundamental physics. In this online seminar, Adam Riess will review recent and expected progress.

Adam Riess is a distinguished professor at the Johns Hopkins University and the Space Telescope Science Institute (STScI) in Baltimore. He won the Nobel Prize in Physics in 2011 (jointly with Brian Schmidt and Saul Perlmutter) for the discovery that the expansion of the universe is accelerating. Riess had studied at MIT and received his PhD from Harvard University in 1996. He then moved to UC Berkeley as a Miller Fellow, afterwards he joined tSTScI. In 2006, he became a full professor at Johns Hopkins University. In 2016 he was awarded a Bloomberg Distinguished Professor there. Since 1998, Adam Riess had led the High-z Supernova Search Project jointly with Brian Schmidt. Through discovering and monitoring supernovae of Type Ia, they provided evidence that the universe’s expansion rate is accelerating. Adam Riess has received numerous prizes and awards for his research,  e.g.  the Astronomical Society of the Pacific’s Robert J. Trumpler Award in 1999, the American Astronomical Society’s Helen B. Warner Prize in 2003, the Raymond and Beverly Sackler Prize in 2004, the Shaw Prize in Astronomy in 2006 (jointly with Saul Perlmutter and Brian Schmidt), and the Gruber Cosmology Prize in 2007 (with the High-Z Team).

This webinar was recorded on May 20, 2021