Paper suggests warming will end up closer to double the IPCC estimates
Researchers reconstructed past 15 million years' atmospheric carbon dioxide levels using sterane and phytane compounds in California coast sediment. Findings suggest higher climate sensitivity than IPCC estimates, aiding climate trend modeling.
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Researchers have reconstructed the atmospheric carbon dioxide (pCO2) values over the past 15 million years using sterane and phytane compounds found in sediment. The study, conducted at a single continuous site on the California coast, shows a steady decline in pCO2 values from 650 ± 150 to 280 ± 75 ppmv, correlating with a global temperature decrease. These findings suggest an Earth system sensitivity of 13.9 °C and an equilibrium climate sensitivity of 7.2 °C per doubling of pCO2, higher than IPCC estimations. By analyzing phytoplankton biomarkers, the researchers aim to refine the understanding of the pCO2-temperature relationship from the mid-Miocene to late Pleistocene. The δ13C records of general phytoplankton biomarkers (GPBs) at the study site indicate a global signal for pCO2 levels over the past 15 million years. This approach using GPBs offers a promising tool to extend pCO2 proxies further back in time, potentially spanning the Phanerozoic era. The study highlights the importance of geologic data in providing insights into past climate conditions and modeling future climate trends.
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2 commentsAs the paper notes in its closing discussion (quoted below), it seems to support the theory that there is much more warming to come. This paper also reinforces the conclusions of Hansen et al.'s Global Warming in the Pipeline (linked below) and a growing (but admittedly controversial) body of academic literature which finds that we may indeed be heading to a "hothouse Earth" future.
When we again weigh each sensitivity by the percent-area for the Earth, our global average ECS is 7.2 °C per doubling of CO2, much higher than the most recent IPCC estimates of 2.3 to 4.5 °C and consistent with some of the latest state-of-the-art models which suggest ca. 5.2 °C
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