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Silicate rock weathering represents a negative feedback mechanism that regulates atmospheric CO₂ levels on geological timescales. Here, the authors show that a diminished silicate weathering feedback may have set the stage for greenhouse warming and ocean acidification during the Middle Eocene, ~40 million years ago.

High fidelity benthic foraminifera oxygen isotope records reveal that variations in Earth’s orbit are the primary pacemaker of change in early Antarctic ice ages and caused these ice ages to sometimes end abruptly.

The growth of ice on Antarctica about 34 million years ago affected sea level. A combination of modelling and marine sediment analyses shows that sea level near the developing ice sheet first fell and then rose as a result of crustal deformation imposed by the ice growth.

Exceptionally high resolution records of environmental change across the Palaeocene/Eocene boundary from two sediment sections in New Jersey find that the onset of environmental change and surface–ocean warming preceded the input of greenhouse gases by several thousand years. This sequence is consistent with the proposal that warming of the deep ocean caused the dissociation of submarine gas hydrates, which released massive amounts of methane.

The East Antarctic ice sheet is considered to be largely insensitive to temperature changes in the Southern Ocean. Marine sediment records indicate the East Antarctic ice sheet repeatedly retreated by several hundred kilometres during intervals of Pliocene warmth.

Deep-ocean oxygenation patterns consistent with an active Atlantic meridional overturning circulation emerged following the Eocene-Oligocene transition about 34 million years ago, according to biomarker records from the northwest North Atlantic.

A detailed reconstruction of the calcium carbonate compensation depth—at which calcium carbonate is dissolved—in the equatorial Pacific Ocean over the past 53 million years shows that it tracks ocean cooling, increasing as the ocean cools.

Northern and Southern hemisphere temperatures were decoupled during the Eocene/Oligocene transition, suggests a sea surface temperature record from the North Atlantic.

Multi-proxy core data and model simulations support the presence of temperate rainforests near the South Pole during mid-Cretaceous warmth, indicating very high CO₂ levels and the absence of Antarctic ice.

A reconstruction of temperatures along the Wilkes Land coast of Antarctica during the early Eocene epoch shows that the climate supported the growth of near-tropical forests and that winters were very mild and essentially frost-free.

Ocean heat is important in forcing ice sheet retreat, yet past ocean temperature data from proximal ice sheet locations are sparse. Here, the authors present temperature reconstructions from the Wilkes Land subglacial basin during the mid-Miocene, and show that warm waters sustained ice sheet retreat 17–14.8 Ma.

A 500,000-year-long period of warmth in the middle Eocene was marked by high atmospheric carbon dioxide concentrations and prolonged dissolution of carbonate in the deep oceans. Numerical simulations attempting to capture these features identify gaps in our understanding of the causes of this and similar perturbations.

Geophysical and geological data reveal increased ice-sheet variability and surface meltwater—possibly analogous to future conditions—offshore of the Aurora subglacial basin of East Antarctica during warm climate intervals of the past 50 million years.

A 26-million-year record of equatorial sea surface temperatures reveals synchronous changes of tropical and polar temperatures during the Eocene epoch forced by variations in concentrations of atmospheric carbon dioxide, with a constant degree of polar amplification.