Core Insights - The research published in the journal "Nature Geoscience" reveals that changes in ocean sulfate concentrations can alter methane consumption methods, shedding light on the carbon cycle mechanisms behind the extreme global warming and ocean acidification during the Paleocene-Eocene Thermal Maximum (PETM) 56 million years ago [1] Group 1: Methane Consumption and Carbon Cycle - Approximately 90% of methane in modern oceans is utilized by microorganisms in sediments under anoxic conditions, producing alkaline substances that mitigate ocean acidification [1] - During the PETM, the sulfate concentration in Arctic seawater was less than one-third of modern levels, leading to a shift where oxygen-loving bacteria began to "rapidly burn" methane, directly consuming oxygen and releasing carbon dioxide [1] - The reconstruction of carbon dioxide concentrations based on molecular traces from marine phytoplankton indicates that during the PETM recovery period, Arctic ocean CO2 levels were 200-700 ppm higher than the global average, indicating a transition from CO2 absorption to emission [1] Group 2: Implications for Arctic's Role in Carbon Cycle - The reduction in seawater salinity and sulfate led to methane being decomposed solely through "rapid burning," resulting in significant carbon dioxide production [1] - This fundamentally altered the Arctic's role in the global carbon cycle, transforming it from a carbon sink to a greenhouse gas emission source [1]

Core Insights - The research reveals a significant global warming event that occurred 56 million years ago, known as the Paleocene-Eocene Thermal Maximum (PETM), which was triggered by a rapid release of carbon dioxide [1][2] - The study highlights a precursor event, a carbon isotope negative anomaly (POE), which served as a warning signal before the PETM, indicating a complex relationship between these two events [1][2] Group 1: Research Findings - The research team utilized sedimentary layers from the Kuzi Gongsu profile in Xinjiang, China, to analyze historical climate data, confirming the synchronous nature of the POE on a global scale [2] - The POE event lasted a shorter duration with a minor carbon isotope negative shift of approximately 1‰ to 2‰, leading to slight warming, shallow marine acidification, and changes in microbial communities [2] - During the POE, the carbon emission rate was about 1 billion tons per year, comparable to the fossil fuel emissions of the 1960s, resulting in a 40% increase in atmospheric CO2 concentration over a century to a millennium [2] Group 2: Implications for Current Climate - The historical analysis serves as a natural experiment demonstrating the consequences of rapid carbon release, with a warning that current human activities are accelerating CO2 emissions at an even faster rate [3] - The research emphasizes the urgency of reducing carbon emissions before reaching a critical threshold that could lead to catastrophic climate events similar to the PETM [3]