# Maureen Raymo

Maureen E. Raymo (born 1959) is an American paleoclimatologist and marine geologist. She is the Co-Founding Dean Emerita of the Columbia Climate School and the G. Unger Vetlesen Professor of Earth & Environmental Sciences at Columbia University. From 2011 to 2022, she was also Director of Lamont-Doherty Earth Observatory's (LDEO) Core Repository and, until 2024, was the Founding Director of the LDEO Hudson River Field Station. From 2020 to 2023, she was first Interim Director then Director of Lamont-Doherty Earth Observatory, the first climate scientist and first female scientist to head the institution.
Raymo has done pioneering work on the origin of the ice ages, the geologic temperature record of the Earth, and past sea level change, publishing over 100 peer-reviewed scientific articles. Her work underlies fundamental ideas in paleoceanography including the uplift weathering hypothesis, the "41,000-year problem," the Pliocene sea-level paradox, and the Lisiecki-Raymo δ18O stack.
In 2014, Raymo became the first woman to win the Wollaston Medal for geology, which had been awarded for 183 years at the time. She was described in her nomination as "one of the foremost and influential figures in the last 30 years."

## Early life and education

Raymo was born in Los Angeles, and at the age of eight she sailed with her family to Europe on the ocean liner S.S. United States and resolved to dedicate her life to studying the ocean. The books and films of Jacques Cousteau were also important early influences. Raymo attended Oliver Ames High School in Easton, Massachusetts, where she graduated with the Bausch and Lomb Honorary Science Award, and then attended Brown University, receiving her Sc.B. Geology in 1982. After a brief stint working in a lab, she then attended Columbia University, where she earned her M.A. in geological sciences in 1985, her M.Phil. in geology in 1988, and her Ph.D. in geology in 1989.

## Career
### Early climate research

Raymo is known for developing (along with William Ruddiman and Philip Froelich) the Uplift-Weathering Hypothesis. According to this hypothesis, tectonic uplift of areas such as the Himalayas and Tibetan plateau over the last 40 million years contributed to surface cooling and thus the Ice Ages. Mountain uplift enhances the chemical weathering of minerals, a process that removes carbon dioxide from the atmosphere. The resulting cooling led to the growth of large ice sheets at both poles. Raymo and her colleagues initially suggested that measuring the proportions of isotopes of strontium (Sr) in deep ocean sediments could substantiate the Uplift-Weathering Hypothesis but soon recognized that ambiguities in the sources of strontium to the ocean existed. Over 35 years later, the hypothesis continues to be debated and studied with many new lines of evidence proposed. Their proposed mechanism of CO$_2$ removal, the chemical weathering of mechanically crushed rock, is also the scientific basis behind projects which aim to remove anthropogenic CO$_2$ from the atmosphere via artificially enhanced chemical weathering.
Raymo is known for her research using sedimentological and geochemical data from deep sea cores to better understand how the ocean's thermohaline circulation changed in the past, as well as how Earth's Milankovitch cycles have influenced the pacing of ice ages over the Pleistocene and Pliocene. Raymo's Anti-phase Hypothesis explains the 41,000 year pacing of Earth's climate cycles from 3 to 1 million years ago as due to the out-of-phase response of the northern and southern polar ice sheets to orbital precession at this time.
Raymo has also made contributions to the stratigraphy and dating of the past by means of oxygen isotope analysis of foraminifera from deep ocean sediments. This included publishing the first continuous oxygen isotope stratigraphy and time scale of the northern hemisphere Ice Ages from DSDP Site 607. In 2005, with her post-doc Lorraine Lisiecki who led the project, Raymo published the widely adopted 5-million-year LR04 benthic isotope stack which defines Marine isotope stages and continues to be the chronological benchmark against which most studies of the last 5.5 Ma are measured.
In 1996, Raymo published the first paleo-CO$_2$ estimate for the Middle Pliocene Warm Period using carbon isotopes of marine organic matter. This was a time three million years ago when global temperatures were about 2-3 °C above preindustrial levels and their CO$_2$ estimate, between 350 and 400 ppm, later became the inspiration for the name of the activist organization 350.org which advocates for a return to 350 ppm as a safe level of carbon dioxide in the atmosphere.

### Sea level research

In an analysis of collapsed polar ice sheets during the stage 11 Marine Isotope Interglacial (MIS), Raymo and Jerry X. Mitrovica computed global sea-level variations over the past 500 kyr. In their analysis, they assumed that the melting of the East Antarctic Ice Sheet (EAIS) and the Greenland Ice Sheet (GIS) happened towards the end of this interglacial period. One of the methods they used in their examination involved using a “gravitationally self-consistent theory”. Additionally, the researchers performed a Monte Carlo parameter where they observed mantle viscosity, lithospheric thickness, and the duration of the break during MIS 11 (Raymo & Mitrovica, 2012). Raymo and Mitrovica have said that employing this method “yields a preferred bound on the peak eustatic sea level (ESL) during MIS 11”. Understanding the durability of existing ice sheets amidst climate change remains a significant concern for societal safety.
During the PLIOMAX project, Raymo formulated a method for correcting shorelines during the Pliocene period, for post-depositional isostatic changes (PLIOMAX, n.d.). One of the main hurdles the PLIOMAX project faced was the ability to adjust and verify the model performance under CO$_2$ and climate conditions (PLIOMAX, n.d.). The accuracy of accessible paleoclimate data hindered these factors as mentioned earlier (PLIOMAX, n.d.). In another analysis, Raymo and her colleagues examined how polar ice sheets evolved during previous warm periods, specifically during the Pliocene period. For their research, the scientists examined existing evidence of previous sea levels and ice sheet constructions (Dutton et al., 2015). Despite many geological advances in the understanding of global mean sea level during previous warm periods, potential research hindrances still exist for future paleoclimate researchers. For instance, the peak heat temperatures during previous warm periods may have varied on the span of the respective interglacial period, which suggests that warm periods that lasted thousands of years may not represent “equilibrium conditions for the climate-cryosphere system” (Dutton et al., 2015). Additionally, it is currently not possible for researchers and scientists to make exact estimates of peak global mean sea level during the Pliocene period.
In a research paper by Raymo and her colleagues, they explained that the majority of existing sea level projections focus on shorter timelines of less than 2000 years, however, longer timeline projections are critical for predicting potential future sea-level heights to effectively develop long-term sea level defense infrastructure (Kemp et al., 2015). The demand to present location-specific details regarding future sea level projections in the midst of climate change is a critical aspect of climatology research because of the growing concentration of socioeconomic and residential activity along global coastlines.

## Awards and honors

In 2002, she was included by the illustrated magazine Discover in a list of the 50 most important women in science and in her nomination for the Wollaston Medal, Professor James Scourse described her as "one of the foremost and influential figures in the last 30 years...She's been an important role model to women scientists—you can get to the top. "$^.$ Following this, in 2003 she became a fellow of John Simons.
Raymo has won various prizes for her scientific work, including becoming in 2014 the first woman to be awarded the prestigious Wollaston Medal - the highest award of the Geological Society of London. In 2014, she received the Milutin Milankovic Medal at the European Geosciences Union’s annual meeting for her use of geochemistry, geology and geophysics to solve paleoclimatology’s big problems. In 2016 she was elected a member of the National Academy of Sciences. As well, in 2017 Raymo became a fellow of the Explores Club and became and received the Honoris Causa from the University of Lancaster, Great Britain. In 2019 she was awarded the Maurice Ewing Medal by the American Geophysical Union. Raymo is a fellow of the American Geophysical Union and the American Association for the Advancement of Science. In 2022 she was elected as a Member of the Royal Swedish Academy of Sciences, Class for Geosciences.