Dan Lunt EGU 2013Dan Lunt
Can Cretaceous and Eocene Data Inform Estimates of Future Climate Sensitivity?
Dan Lunt, Claire Loptson, Paul Markwick
Introduction Using the palaeo to inform the future The Cretaceous and Eocene Questions to be addressed
Results Experimental Design Results
Summary and future directions
Dan Lunt EGU 2013Dan Lunt
Introduction – using the palaeo to inform the future
QUALITATIVE INFORMATION
QUANTITATIVE INFORMATION
PALAEO DATAe.g. existence of fossilised leaves in Cretaceous Antarctica
e.g. ice core CO2 records
e.g. proxy reconstructions of temperature and CO2
provide estimates of past climate sensitivity[see Rohling et al, 2012]
PALAEO MODEL-DATA COMPARISONS
e.g. model-data comparisons reveal model strengths and weaknesses
e.g. weighting future model simulations according to palaeo model-data comparisons
+ ‘analogues’ and representation of long-term feedbacks in models
Dan Lunt EGU 2013Dan Lunt
Introduction – using the palaeo to inform the future
QUALITATIVE INFORMATION
QUANTITATIVE INFORMATION
PALAEO DATAe.g. existence of fossilised leaves in Cretaceous Antarctica
e.g. ice core CO2 records
e.g. proxy reconstructions of temperature and CO2
provide estimates of past climate sensitivity[see Rohling et al, 2012]
PALAEO MODEL-DATA COMPARISONS
e.g. model-data comparisons reveal model strengths and weaknesses
e.g. weighting future model simulations according to palaeo model-data comparisons
+ ‘analogues’ and representation of long-term feedbacks in models
Dan Lunt EGU 2013Dan Lunt
“Warm Climates of the Past – A lesson for the future?”
Special Issue of Phil Trans A
All papers now ‘in press’
Including contribtions from:DeConto, Dowsett, Foster, Hansen, Haywood, Kiehl, Lunt, Otto-Bliesner, Pagani, Pancost, Pearson, Valdes, Zachos, Zeebe.
Early Eocene, ~55 - 50 Ma
Mid-Pliocene, ~3.3 - 3 Ma
Last Interglacial, 135-130 ka
...future, 2100
Introduction – using the palaeo to inform the future
Dan Lunt EGU 2013Friedrich et al (2012) and Zachos et al (2008)
Global temperature evolution over the last ~100 million years
Introduction – Cretaceous and Eocene
Dan Lunt EGU 2013
mid-Cretaceous, ~ 100 million years ago © Bob Nicholls. A depiction of Alexander Island, Antarctica, during the Cretaceous
early Eocene, ~50 million years ago
Introduction – Cretaceous and Eocene
Lunt et al, 2012; Data compiled by Tom Dunkley Jones
Dan Lunt EGU 2013Dan Lunt
Introduction – Cretaceous and Eocene
CO2 forcing[Honisch et al, 2012]
Solar forcing[Gough, 1981]
Dan Lunt EGU 2013Dan Lunt
Introduction – Cretaceous and Eocene
Research Questions....
(1)How does baseline climate change through these ‘deep time’ periods?
(2)How does Cretaceous/Eocene climate sensitivity compare with modern?
(3) What are the implications of the above for proxy reconstructions of climate sensitivity at specific core sites?
Dan Lunt EGU 2013Dan Lunt
Results – Experimental Design
HadCM3L (3.75 x 2.5 degrees in atmosphere and ocean)
Initial ocean condition = idealised cosine in temperature and salinity; ocean at rest
TRIFFID dynamic vegetation
Dan Lunt EGU 2013Dan Lunt
CO2 forcing[Honisch et al]
Results – Experimental Design
Dan Lunt EGU 2013Dan Lunt
Results – Cretaceous global mean temperature
Puceat et al, 2003
Dan Lunt EGU 2013Dan Lunt
Results – Cretaceous temperature variations at a single site
Dan Lunt EGU 2013Dan Lunt
Results – Cretaceous/Eocene/modern climate sensitivity
Eocene (4.7 oC) Maasthrichtian (2.5 oC)
Future (4.4 oC)
Dan Lunt EGU 2013Dan Lunt
Conclusions
There is a state dependence of climate through the Cretaceous (~ 1.5 oC).
There is a state dependence of climate sensitivity through the Cretaceous and Eocene (~ 2 oC)
For these time periods....
(1) Inferring climate trends from single paleo data points is dangerous. Depending on region, the error (even after correcting for paleolat/lon) can be as much as 8 oC.
(2) Inferring climate sensitivity from paleo data is dangerous, Depending on time period, the error (even if you can estimate the global mean and forcing correctly), can be as much as x2.
Dan Lunt EGU 2013Dan Lunt
Introduction – using the palaeo to inform the future
QUALITATIVE INFORMATION
QUANTITATIVE INFORMATION
PALAEO DATAe.g. existence of fossilised leaves in Cretaceous Antarctica
e.g. ice core CO2 records
e.g. proxy reconstructions of temperature and CO2
provide estimates of past climate sensitivity[see Rohling et al, 2012]
PALAEO MODEL-DATA COMPARISONS
e.g. model-data comparisons reveal model strengths and weaknesses
e.g. weighting future model simulations according to palaeo model-data comparisons
+ ‘analogues’ and representation of long-term feedbacks in models
Dan Lunt EGU 2013Dan Lunt
Future Work
Much still to do....
Complete ‘matrix’ of 2x and 4x simulations through Cretaceous to modern.
Ensure full consistency between all simulations.
Explore other uncertainties (e.g. parametric (ensembles), structural (e.g. CCSM), boundary conditions...etc )
Model-data comparisons where possible.
Then....possible weighting of future simulations
+ (most importantly??!!)
Process-based understanding of simulations.