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Tipping point

The Palaeocene-Eocene Thermal Maximum: anatomy of a tipping point Mike Stephenson, Robert Knox, Melanie Leng, Chris Vane, Jim Riding. Tipping point. point at which a slow gradual change becomes irreversible and then proceeds with gathering pace

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Tipping point

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  1. The Palaeocene-Eocene Thermal Maximum: anatomy of a tipping pointMike Stephenson, Robert Knox, Melanie Leng, Chris Vane, Jim Riding

  2. Tipping point • point at which a slow gradual change becomes irreversible and then proceeds with gathering pace • point in the evolution of the earth's climate leading to irreversible change • When a small (unnoticed) thing happens which is enough to precipitate huge things happening….which we can’t repair

  3. Is the climate tipping? • Some scientists e.g. James Hansen, -tipping point already reached – CO2 at 385 ppm • Some say - tipping point difficult to predict for non-linear, complex system • Some say - political slogan - instil fear in policy makers and largesse in science funders

  4. Can we stop the tipping? • Man made global warming - changing the composition of atmosphere by emission of carbon dioxide and methane. • Remedial action - reduce greenhouse gas. • Is this a reasonable assumption?

  5. Research: understand tipping point • rates of change in biogeochemical cycles • change in extreme events not seen in the last 10k yrs • negative feedbacks that bring the system back to normal dynamic equilibrium

  6. Palaeocene-Eocene Thermal maximum: natural laboratory

  7. Palaeocene-Eocene Thermal Maximum: why it’s important • NOW - • injection CO2 into atmosphere. • changes predicted extreme, 5.6° C increase in the next one hundred years • CO2 atmospheric concentrations higher than at any time during the Quaternary. • PETM • similar magnitude CO2 and temperature increase • some of the remnants of the changes are preserved in the rocks. • Comparison follows

  8. Comparison: CO2 • Drax B - 7% of England's electricity; lifetime emission 1 Gt • China emissions 3 Gt/yr • Leman Sandstone Formation 3Gt storage capacity • Bunter Sandstone Formation 15 Gt • PETM caused by 1500 Gt of methane carbon from decomposing gas-hydrate reservoirs (Sluijs 2006) • PETM ~ equivalent of 4-8 times the anthropogenic carbon released since start of the industrial era

  9. What is preserved? Clay Layer Rocks/lithofacies Forams Dinoflagellates Various geochemical evidence

  10. What does it suggest?Temperature increase • TEX86 palaeothermometer • O isotope excursions in foram calcite and terrestrial carbonates • Increased Mg/Ca value in forams • Poleward migrations of tropical marine plankton, terrestrial plants, and mammal migrations

  11. Carbon cycle change • 2.5 – 6 ‰ carbon isotope excursion • Believed to represent rapid injection of 13C depleted carbon into the global carbon pool • Conjunction of warming and excursion: greenhouse gas cause?

  12. What does the CIE excursion look like? high low Gradual recovery Steep beginning

  13. Bass River, Sluijs (2006)warm phytoplantontemp riseboth precede the CIEOnly biogenic methane (C = -70‰ enough to create a CIE of this size Apectodinium peak and temperature rise (as indicated by TEX86) preceded the CIE Did heating trigger methane hydrate release leading to the CIE?

  14. BP Well 22/10a-4 Middle of N. Sea

  15. Well 22-10a/4 • North Sea well - probably the most expanded section known – chance to unravel the CIE • δ13Corg • Palynology/palynofacies • Detailed lithofacies • Organic geochemistry • Inorganic geochemistry

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