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?
ICP, Sitges, 2013
(1) Introduction
Last 150 Ma:
Major climate trends,
+ ‘events’
What is the role of
solar forcing vs.
palaeogeographic
forcing vs. carbon
cycle forcing?
Data from Friedrich et al (2012)
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(1) Introduction
CO2 proxies
Palaeogeography
Solar forcing
Maps from Scotese’s ‘Paleomap’
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(2a) Previous modelling work
(paleogeography)
‘Real’ models...
e.g. Westward flow through Tethys.
Luyendyk et al, (1972)
e.g. significant effect on temperature
due to continental area (i.e. sea
level), and potential importance of
desert regions.
Energy balance
models...
Barron et al (1980)
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(2a) Previous modelling work
(paleogeography)
Atmosphere-only
models...
e.g. changes in high latitude land
area and topography most important
drivers...
Barron and Washington (1984)
e.g. Eastward flow through Tethys.
Barron and Peterson (1990)
Ocean-only
models...
e.g. Eocene
(from SH)
vs. Miocene
(from NH)
ocean
overturning
Bice et al (2000)
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(2a) Previous modelling work
(paleogeography)
e.g. Atlantic rifting leads to
warming, plus salinity
changes usually interpreted
as signalling middle
Cretaceous warmth.
Poulsen et al (2003)
Intermediate
complexity
models...
e.g. break-up of continent
leads to increased seasonality
Donnadieu et al (2006)
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(2a) Previous modelling work
(paleogeography)
Atmosphere-ocean
models...
e.g. modelled Eocene meridional
temperature gradients interpreted as
being too great.
Huber and Sloan (2001)
e.g. modelled seasonality too large
wrt. CLAMP, for 3 different
Cretaceous palaeogeographies
Spicer et al (2008)
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(2a) Previous modelling work (CO2)
e.g. Eocene climate sensitivity
increases at higher temperatures –
due to non-linearities in both forcing
and cloud feedbacks.
Caballero and Huber (in press)
e.g. Cretaceous climate sensitivity
enhanced due to vegetation
feedbacks. Zhou et al (2012)
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(3a) Questions to be addressed
Current paradigm:
Paleogeographical 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 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”).
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(3b) Experimental Design
Palaeogeographies
provided by Getech
and Paul Markwick
Animation removed.
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.
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(3b) Experimental Design
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(3b) Experimental Design
The model: HadCM3L (with vegetation)
“state-of-the-art”....not.
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(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.
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(3b) Experimental Design (consistent across all simulations)
Phase 2
Phase 3
Phase 4
50-years
400-years
57-years
500-1000 years
4xCO2
TRIFFID
Solar constants
Ozone
concentrations
Lakes
Deep ocean temperature
Phase 1
Pre-industrial CO2
Pre-industrial SSTs
Paleogeography's
Uniform Veg
Creation of islands
Baratropic
stremfunction
No Ice + 2 x CO2
Ice + 2 x CO2
Ice + 4 x CO2
Simulation spinup – from Alex Farnsworth
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(4) Results
Global means...
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(4) Results
SSTs...
e.g.
Maximum warmth
shifts from W. Pacific
to E. Indian ocean in
Late Eocene.
Animation removed.
Zonal mean relatively
constant.
ENSO is a constant
feature.
Winter Arctic and
Southern Ocean
seaice for all time
periods.
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(4) Results
Regions of deep water formation...
e.g.
N. Pacific deep water
formation in earliest
Cretaceous, gone by
Middle Cretaceous.
Animation removed.
Mid and late
Cretaceous and early
Eocene little mixing.
North Atlantic deep
water formation kicks
off ~40 Ma.
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(4) Results
Vegetation...
e.g.
Expansive N and S
American deserts in
early Cretaceous.
Animation removed.
‘Green’ Sahara
develops in late
Eocene.
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(4) Results
Single sites...
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(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:
Marine
Terrestrial
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(4) Results
Climate Sensitivity
Only one (two) ‘true’ sensitivity –
Earth System Sensitivity. Either to (a) Wm-2 or (b) ΔCO2
This is neither! Modellers’ imagination ‘Charney’+vegetation.
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(4) Results
Climate Sensitivity
3.3oC
2.8oC
3.0oC
3.0oC
3.2oC
2.8oC
2.5oC
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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’ CO2 signal could be
obtained.
 Climate Sensitivity is a function of palaeography, varying by 30%
through the late and mid Cretaceous.
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(5) Future work
CESM simulations
Early Cretaceous grid
Late Cretaceous grid
Early Cretaceous DMS emissions
Modern DMS emissions
Modern DMS emissions
“paleo-tised”
Late Cretaceous DMS emissions
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(5) Future work
NERC project:
Cretaceous-Paleocene-Eocene: Exploring Climate and Climate Sensitivity
 Complete CO2 sensitivities
 Ice sheets [e.g. role of CO2, gateways and ice sheets at E-O boundary]
 Model internal parameter sensitivity studies.
 Data compilations (Stuart Robinson, Oxford).
Back-out model-derived CO2 record
Sagoo et al, Phil Trans, in press.
Kiehl et al, Phil Trans, in press.
Lunt et al, Phil Trans, in press.
.
 Equivalent future simulations
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(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
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Using the palaeo to inform the future
Early Eocene, ~55 - 50 Ma
Mid-Pliocene, ~3.3 - 3 Ma
“Warm Climates of the Past –
A lesson for the future?”
Last Interglacial, 135-130 ka
Special Issue of Phil Trans A
All papers now ‘in press’
...future, 2100
Including contributions from:
Badger, DeConto, Dowsett, Foster,
Hansen, Haywood, John, Kiehl, Lunt, OttoBliesner, Pagani, Pancost, Pearson,
Sagoo, Valdes, Zachos, Zeebe, Zhang.
Dan Lunt
http://www.paleo.bris.ac.uk/~ggdjl/warm_climates.html
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(4) Results
Precipitation...
e.g.
Amazon desiccates in
late Oligocene.
East Asian monsoon
system initiates in
middle Eocene.
Animation removed.
North Atlantic storm
tracks intensify in late
Eocene.
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