RCN: Improving reconstructions of Cenozoic pCO2 and temperature change

Lead PI: Dr. Baerbel Hoenisch, Pratigya Polissar

Unit Affiliation: Geochemistry, Lamont-Doherty Earth Observatory (LDEO)

October 2016 - September 2020
Project Type: Research

DESCRIPTION: The contribution of atmospheric carbon dioxide (pCO2) to Earth's greenhouse effect has been known for more than a century, yet the detailed impacts of higher atmospheric CO2 concentrations on climate, terrestrial, and marine ecosystems are still subject to uncertainty. Earth history can aide scientists in improving their understanding of the interaction between pCO2 and global climate change, by providing records of past variations in pCO2 and climate recorded in the chemical composition of fossil shells and molecules. In the geologic past, Earth experienced profound changes in pCO2 and climate, but reconstructions remain challenging. This is due to the fact that many of the fossil-producing organisms are now extinct, landscapes have changed, and the chemical composition of the oceans and atmosphere have changed. While researchers actively explore individual archives and model sensitivities, less effort has been spent on developing a broader view of relative strengths and weaknesses of different approaches. This research coordination network will bring the paleoclimate/palcoeanographic research community together with the goal of openly recognizing uncertainties, constructively and jointly working to reduce them, and advancing the understanding of past and future climate change. To achieve this goal, two workshops will be held, which will bring together established and future specialists in reconstructing and modeling paleo-pCO2 from terrestrial and marine archives. The workshops will focus on validation opportunities for pCO2 proxies and carbon cycle models over the last 65 million years of earth history. Particular attention will be paid to proxy and model cross-calibrations and sensitivity studies in select time periods. A paleo-pCO2 database will be established, and position papers on best practices guidelines will be published. Opportunities will be discussed for carbon cycle and biogeochemical models to improve data syntheses and identify regions for desirable data additions. To improve capacity building within the US, up to four US scientists per year will be provided with an opportunity to enter an analytical and model training program, where they will learn new techniques from experts in the field. To ascertain that all research aspects and demographics are appropriately covered, a 16-member steering committee will both nominate expert workshop participants but also select promising but less well established candidates from an (inter-)national applicant pool.

OUTCOMES: A paleo-CO2 database has been established in NOAA's NCDC, including all publiushed Cenozoic paleo-CO2 estimates from terrestrial and marine archives. This database is now being evaluated by a group of experts under a follow-up study funded by the Heising-Simons Foundation, which also funds the development of a website explaing the data.