Climate of the Past 20th Anniversary: Greenhouse Gases and Climate Sensitivity

To mark its 20th anniversary, Climate of the Past, an interactive journal of the European Geosciences Union, is launching a special webinar series celebrating two decades of leading paleoclimate science.

Each webinar will emphasize the journal’s scientific diversity and impact, featuring two invited talks of 30 minutes from leading researchers across different areas of paleoclimate science. Talks will be followed by a live 30 minutes Q&A session, allowing for discussion and engagement with the broader community.

Earth’s climate and environmental conditions have changed dramatically through geologic time, and the concentration of atmospheric greenhouse gases is an important driver of such change. Ice-core and proxy-based reconstructions of past carbon dioxide levels allow a better understanding of its role in past natural climate change and the dynamics of the Earth system.

Climate sensitivity, commonly defined as the global average warming resulting from a doubling of atmospheric CO₂, depends on a series of complex feedback processes that include changes to cloud formation, vegetation, and ice cover. Coupled changes in past climate and radiative forcing can be used to provide direct empirical constraints on Earth’s climate sensitivity — the most important parameter in projecting future climate change from anthropogenic carbon emission.

Talks:

James Rae (University of St. Andrews) - Refining reconstructions of atmospheric CO₂ and climate sensitivity from climates of the past.

Climates of the past provide invaluable insights into global change under elevated CO₂, including modes of Earth system functioning and climate sensitivity. CO₂ reconstructions are central to these efforts and have seen concerted development in recent years.

Here I present an overview of the current state of CO₂ reconstruction from the mid-Pleistocene to the PETM and beyond. These studies demonstrate CO2’s pervasive control on global climate, including the coupling of declining CO₂ levels and glacial intensification in both the Pleistocene and the Ordovician, while highlighting the need for further research to better resolve and refine our fossil record of the atmosphere.

Jessica Tierney (The University of Arizona) – Estimating climate sensitivity from the paleoclimate record.

Paleoclimates are crucial for constraining Earth’s climate sensitivity (ECS), especially the upper tail of the distribution which is not well constrained by historical observations. However, changing boundary conditions (ice sheets, vegetation, and continental configuration) complicate how we use past climates to infer present-day ECS.

In this talk I’ll discuss recent approaches we’ve taken to tackle this problem including addressing the paleo- “pattern effect”. So far, we’ve discovered ancient climates have more amplifying feedbacks than the present day, which raises a question as to whether the present climate sits represents an ECS minimum.

Conveners:

Christo Buizert & Eric Wolff.

Speakers:

James Rae (University of St. Andrews) - My research focuses on reconstructing past climate change and its causes. I'm particularly interested in the cause of recent glacial-interglacial cycles, and climate changes over the Cenozoic. To study these questions I use geochemical measurements on fossils, sediments, water and ice, with a special focus on the boron isotope proxy for pH. I interpret these data with the help of a variety of numerical models. I'm also fascinated by biomineralisation processes in corals and foraminifera, and the insights that geochemistry offers into calcification and ocean acidification.

Jessica Tierney (The University of Arizona) - I study past climate change (paleoclimatology) to learn about how the Earth system works and what's in store for the future. My research group focuses on studying past climates over a variety of timescales, using organic geochemical techniques and statistical climate reconstruction. I'm proud to be a Packard Foundation Fellow, an American Geophysical Union Fellow, a recipient of the National Science Foundation Alan T. Waterman award and a lead author on the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment report.

Register for this online event here.

If you have any questions about ‘Climate of the Past 20th Anniversary: Greenhouse Gases and Climate Sensitivity’, please contact us via webinars@egu.eu.