1. AGU, San Francisco, 2013 Modelled insights into climate dynamics of the Cretaceous and Paleogene greenhouse Dan Lunt, Claire Loptson, Alex Farnsworth, Paul Markwick (1)What is the role of palaeogeography across the Cretaceous and Paleogene? (2)Where can new data be targetted to obtain a ‘pure’ climate signal? (3)How does palaeogeography influence Climate Sensitivity?

2. AGU, San Francisco, 2013 Data from Friedrich et al (2012) (1) Introduction What is the role of solar forcing vs. palaeogeographic (including gateways) forcing vs. carbon cycle forcing? Last 150 Ma: Major climate trends, + variability + ‘events’

3. AGU, San Francisco, 2013 (2) Questions to be addressed Current paradigm:  Paleogeographical / gateway changes less important than greenhouse gas forcing. BUT:  Work mostly focussed on a limited number of time periods  Lack of consistency across simulations  Coarse palaeogeographies  Models have improved SO: (1) What is the role of palaeogeography (including gateways) across the Cretaceous/Paleogene? (2) Where can new data be targetted to obtain a ‘pure’ climate signal? (3) How does palaeogeography influence Climate Sensitivity? (i.e. “state dependency”).

4. AGU, San Francisco, 2013 (3) Experimental Design Palaeogeographies provided by Getech and Paul Markwick Created using similar techniques to those outlined in Markwick (2007), based on published lithologic, tectonic and fossil studies, the lithologic databases of the Paleogeographic Atlas Project (University of Chicago), and deep sea (DSDP/ODP) data. Extensively updated from Markwick (2007), e.g. bathymetry, new rotations, more underlying data. Paleogeographies removed

5. AGU, San Francisco, 2013 (3b) Experimental Design

6. AGU, San Francisco, 2013 (3b) Experimental Design The model: HadCM3L (with vegetation) “state-of-the-art”....not.

7. AGU, San Francisco, 2013 (3b) Experimental Design The model: HadCM3L How good is it for the palaeo? Lunt et al, Clim. Past (2012) Data compiled by Tom Dunkley Jones.

8. AGU, San Francisco, 2013 Phase 1Phase 2Phase 3Phase 4 Deep ocean temperature 50-years400-years 57-years 500-1000 years Pre-industrial CO 2 Pre-industrial SSTs Paleogeography's Uniform Veg Lakes4xCO 2 TRIFFID Solar constants Ozone concentrations Creation of islands Baratropic stremfunction No Ice + 2 x CO 2 Ice + 2 x CO 2 Ice + 4 x CO 2 (3b) Experimental Design (consistent across all simulations) Simulation spinup – from Alex Farnsworth

9. AGU, San Francisco, 2013 (4) Results Global means...

10. AGU, San Francisco, 2013 (4) Results SSTs... e.g. Maximum warmth shifts from W. Pacific to E. Indian ocean in Late Eocene. Zonal mean relatively constant. ENSO is a constant feature. Winter Arctic and Southern Ocean seaice for all time periods. Animations removed

11. AGU, San Francisco, 2013 (4) Results Regions of deep water formation... e.g. N. Pacific deep water formation in earliest Cretaceous, gone by Middle Cretaceous. Mid and late Cretaceous and early Eocene little mixing. North Atlantic deep water formation kicks off ~40 Ma. Animations removed

12. AGU, San Francisco, 2013 (4) Results Vegetation... e.g. Expansive N and S American deserts in early Cretaceous. ‘Green’ Sahara develops in late Eocene. Animations removed

13. AGU, San Francisco, 2013 (4) Results Single sites...

14. AGU, San Francisco, 2013 (4) Results Implications for site targetting... Where are the locations with least paleography-related change; i.e. Where to go for a ‘pure’ CO2 signal: MarineTerrestrial

15. AGU, San Francisco, 2013 (4) Results Climate Sensitivity

16. AGU, San Francisco, 2013 (4) Results Climate Sensitivity 3.3 o C2.8 o C3.0 o C2.8 o C 3.0 o C3.2 o C2.5 o C

17. AGU, San Francisco, 2013 Summary  Cretaceous and Paleogene simulations broadly support the paradigm that carbon cycle dominates over palaeogeography forcing.  BUT, at single sites, the temperature changes due to palaeogeography alone can be very large.  AND, other aspects of the system, such as ocean circulation and vegetation, can also show very large palaeogeographically-driven changes.  Simulations can point to where a ‘pure’ CO 2 signal could be obtained.  Climate Sensitivity is a function of palaeography, varying by 30% through the late and mid Cretaceous.

18. AGU, San Francisco, 2013 (5) Future work CESM simulations Early Cretaceous gridLate Cretaceous grid Modern DMS emissions “paleo-tised” Early Cretaceous DMS emissions Late Cretaceous DMS emissions

19. AGU, San Francisco, 2013 (5) Future work NERC project: Cretaceous-Paleocene-Eocene: Exploring Climate and Climate Sensitivity  Complete CO 2 sensitivities  Ice sheets [e.g. role of CO 2, gateways and ice sheets at E-O boundary]  Model internal parameter sensitivity studies.  Data compilations (Stuart Robinson, Oxford).  Back-out model-derived CO 2 record  Equivalent future simulations Sagoo et al, Phil Trans, in press. Kiehl et al, Phil Trans, in press. Lunt et al, Phil Trans, in press..

20. AGU, San Francisco, 2013 (5) Future work  Complete Neogene simulations.  Role of orbital forcing PMIP working group on ‘pre-Pliocene climates’ Joint venture between data and modelling communities Model output available. Email: d.j.lunt@bristol.ac.uk

21. AGU, San Francisco, 2013Dan Lunt “Warm Climates of the Past – A lesson for the future?” Special Issue of Phil Trans A All papers now ‘in press’ Including contributions from: Badger, DeConto, Dowsett, Foster, Hansen, Haywood, John, Kiehl, Lunt, Otto- Bliesner, Pagani, Pancost, Pearson, Sagoo, Valdes, Zachos, Zeebe, Zhang. Early Eocene, ~55 - 50 Ma Mid-Pliocene, ~3.3 - 3 Ma Last Interglacial, 135-130 ka...future, 2100 Using the palaeo to inform the future http://www.paleo.bris.ac.uk/~ggdjl/warm_climates.html