Polar amplification (PA) is a key uncertainty in climate projections. The factors that dominantly control PA are difficult to separate. Here we provide an estimate for the non-ice-related PA by reconstructing tropical ocean temperature variability from the ice-free early Eocene, which we compare to deep-ocean-derived high-latitude temperature variability across short-lived warming periods. We find a PA factor of 1.7–2.3 on 20 kyr timescales, which is somewhat larger than model estimates.

This paper examines benthic foraminifera, single-celled organisms, at Integrated Ocean Drilling Program Site U1506 in the Tasman Sea from the Late Miocene to the Early Pliocene (between 7.4 to 4.5 million years ago). We described and illustrated the 36 most common species; analysed the past ocean depth of the site; and investigated the environmental conditions at the seafloor during the Biogenic Bloom phenomenon, a global phase of high marine primary productivity.

We assembled a very accurate geological timescale from the interval 47.8 to 56.0 million years ago, also known as the Ypresian stage. We used cyclic variations in the data caused by periodic changes in Earthäs orbit around the sun as a metronome for timescale construction. Our new data compilation provides the first geological evidence for chaos in the long-term behavior of planetary orbits in the solar system, as postulated almost 30 years ago, and a possible link to plate tectonics events.

The symbiont-bearing planktic foraminiferal genera Morozovella and Acarinina were among the most important calcifiers of the early Paleogene tropical and subtropical oceans. However, a remarkable and permanent switch in the relative abundance of these genera happened in the early Eocene. We show that this switch occurred at low-latitude sites near the start of the Early Eocene Climatic Optimum (EECO), a multi-million-year interval when Earth surface temperatures reached their Cenozoic maximum.

In this paper we present records of stable C and O isotopes, CaCO₃ content, and changes in calcareous nannofossil assemblages in a upper Paleocene-lower Eocene rocks now exposed in northeast Italy. Modifications of nannoplankton assemblages and carbon isotopes are strictly linked one to each other and always display the same ranking and spacing. The integration of this two data sets represents a significative improvement in our capacity to correlate different sections at a very high resolution.