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The role of palaeogeography in ‘mid-Pliocene warmth’ (Lunt et al, 2012, EPSL)

The role of palaeogeography in controlling Pliocene climate and climate variability Dan Lunt, Paul Markwick Gavin Foster, Alan Haywood, Claire Loptson, Ulrich Salzmann, Gavin Schmidt, Paul Valdes. The role of palaeogeography in ‘mid-Pliocene warmth’ (Lunt et al, 2012, EPSL)

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The role of palaeogeography in ‘mid-Pliocene warmth’ (Lunt et al, 2012, EPSL)

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  1. The role of palaeogeography in controlling Pliocene climate and climate variabilityDan Lunt, Paul Markwick Gavin Foster, Alan Haywood, Claire Loptson, Ulrich Salzmann, Gavin Schmidt, Paul Valdes • The role of palaeogeography in ‘mid-Pliocene warmth’ (Lunt et al, 2012, EPSL) • How the above “could be improved”. • New work

  2. What is the relative contribution to mid-Pliocene warmth from: • CO2 • Orography • Vegetation • Ice sheets

  3. “PreIndustrial World”: E CO2 = 280 ppmv “Mid-Pliocene World”: Eociv CO2 = 400 ppmv

  4. Set up a number of ‘hybrid’ simulations…. e.g. “Mid-Pliocene World but with pre-industrial ice”: Eocv Factorisation methodology…. our approach “linear approach” “Stein and Alpert (1993) approach”

  5. DT=3.3oC dTco2 = 1.6oC dTorog = 0.7oC dTveg = 0.3oC dTice = 0.7oC

  6. Palaeobotanical data CO2 highly uncertain…but likely below 400ppm BUT…. Better vegetation data… Better palaeogeographic data IPCC (2013) statement on sea level: “Together, the evidence suggests that GMSL was above present levels at that time, but did not exceed 20 m above present (high confidence).”

  7. More realistic paleogeography study… Orographic change: Response of the system: Temperature Precipitation Foster et al, 2010

  8. New paleogeography study… Paleogeographies removed

  9. New paleogeography study…

  10. Temperature: Late Pliocene minus Early Pliocene (paleogeography alone )

  11. BUT, are we even asking the right question? Foster et al, 2010

  12. Conclusions • New factorisation metholodology can be used to determine relative importance of different boundary conditions • Work with old boundary conditions gives: CO2 = 50%, topo = 20%, ice = 20%, veg = 10% • Availability of new boundary conditions means this work should be revisited • Potential for paleogeography to play a role in long-term evolution of Miocene-Pliocene climate change, and timing of onset of Northern Hemisphere Glaciation • More focus on glacial Pliocene climates

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