Publications by authors named "Richard E Zeebe"
Article Synopsis
- The late Paleocene and early Eocene periods were marked by long-term global warming and short, abrupt warming events called hyperthermals, largely influenced by greenhouse gases but possibly affected by other factors like tectonics.
- Researchers analyzed data from planktic foraminifera to reconstruct sea surface temperatures and CO levels, focusing on key events such as the Paleocene-Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM-2).
- Findings indicate a strong connection between CO and temperature, with different carbon sources contributing to the CO increases during these periods, and the emissions from these events are comparable to future projections, highlighting their relevance to current climate change discussions.
The Cenozoic era (66 to 0 million years) is marked by long-term aberrations in carbon cycling and large climatic shifts, some of which challenge the current understanding of carbon cycle dynamics. Here, we investigate possible mechanisms responsible for the observed long-term trends by using a novel approach that features a full-fledged ocean carbonate chemistry model. Using a compilation of pCO, pH, and calcite compensation depth (CCD) observational evidence and a suite of simulations, we reconcile long-term Cenozoic climate and CCD trends.
View Article and Find Full Text PDFAstronomical calculations reveal the Solar System's dynamical evolution, including its chaoticity, and represent the backbone of cyclostratigraphy and astrochronology. An absolute, fully calibrated astronomical time scale has hitherto been hampered beyond ~50 million years before the present (Ma) because orbital calculations disagree before that age. Here, we present geologic data and a new astronomical solution (ZB18a) showing exceptional agreement from ~58 to 53 Ma.
View Article and Find Full Text PDFPlate tectonic controls on atmospheric CO2 levels since the Triassic.
Proc Natl Acad Sci U S A
March 2014
Climate trends on timescales of 10s to 100s of millions of years are controlled by changes in solar luminosity, continent distribution, and atmosphere composition. Plate tectonics affect geography, but also atmosphere composition through volcanic degassing of CO2 at subduction zones and midocean ridges. So far, such degassing estimates were based on reconstructions of ocean floor production for the last 150 My and indirectly, through sea level inversion before 150 My.
View Article and Find Full Text PDFLong-term legacy of massive carbon input to the Earth system: Anthropocene versus Eocene.
Philos Trans A Math Phys Eng Sci
October 2013
Over the next few centuries, with unabated emissions of anthropogenic carbon dioxide (CO2), a total of 5000 Pg C may enter the atmosphere, causing CO2 concentrations to rise to approximately 2000 ppmv, global temperature to warm by more than 8(°)C and surface ocean pH to decline by approximately 0.7 units. A carbon release of this magnitude is unprecedented during the past 56 million years-and the outcome accordingly difficult to predict.
View Article and Find Full Text PDFTime-dependent climate sensitivity and the legacy of anthropogenic greenhouse gas emissions.
Proc Natl Acad Sci U S A
August 2013
Climate sensitivity measures the response of Earth's surface temperature to changes in forcing. The response depends on various climate processes that feed back on the initial forcing on different timescales. Understanding climate sensitivity is fundamental to reconstructing Earth's climatic history as well as predicting future climate change.
View Article and Find Full Text PDFArticle Synopsis
- Atmospheric carbon dioxide levels and climate changes over geological times are influenced by volcanic outgassing and weathering processes, specifically the breakdown of silicate and organic-carbon rocks.
- A study presented a 53-million-year record of carbonate accumulation from the equatorial Pacific Ocean, showing that the calcium carbonate compensation depth has increased from approximately 3.0-3.5 km to 4.6 km over time, indicating long-term ocean cooling and increased weathering.
- The research identified significant fluctuations in the carbonate compensation depth during the middle and late Eocene, attributing these changes to variations in weathering and how organic carbon was delivered to the oceans.