Collapse

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This is the place for discussing the potential collapse of modern civilization and the environment.

Collapse, in this context, refers to the significant loss of an established level or complexity towards a much simpler state. It can occur differently within many areas, orderly or chaotically, and be willing or unwilling. It does not necessarily imply human extinction or a singular, global event. Although, the longer the duration, the more it resembles a ‘decline’ instead of collapse.

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Continuous sterane and phytane δ13C record reveals a substantial pCO2 decline since the mid-Miocene - Nature Communications (www.nature.com)

submitted 3 months ago* (last edited 3 months ago) by eleitl@lemm.ee to c/collapse@lemm.ee

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Abstract

Constraining the relationship between temperature and atmospheric concentrations of carbon dioxide (pCO2) is essential to model near-future climate. Here, we reconstruct pCO2 values over the past 15 million years (Myr), providing a series of analogues for possible near-future temperatures and pCO2, from a single continuous site (DSDP Site 467, California coast). We reconstruct pCO2 values using sterane and phytane, compounds that many phytoplankton produce and then become fossilised in sediment. From 15.0-0.3 Myr ago, our reconstructed pCO2 values steadily decline from 650 ± 150 to 280 ± 75 ppmv, mirroring global temperature decline. Using our new range of pCO2 values, we calculate average Earth system sensitivity and equilibrium climate sensitivity, resulting in 13.9 °C and 7.2 °C per doubling of pCO2, respectively. These values are significantly higher than IPCC global warming estimations, consistent or higher than some recent state-of-the-art climate models, and consistent with other proxy-based estimates.

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[–] eleitl@lemm.ee 1 points 3 months ago

Discussion https://phys.org/news/2024-06-heavier-temperature-previously-thought-analysis.html