Ringberg 2015

WCRP Grand Challenge Workshop: Earth's Climate Sensitivities

March 23-27, 2015

Schloss Ringberg
3700 Rottach-Egern, Germany


Bjorn Stevens, Ayako Abe-Ouche, Sandrine Bony, Gabi Hegerl, Gavin Schmidt, Steve Sherwood and Mark Webb

Participants:   Initiates file download>>> (pdf)
Agenda:          Initiates file download>>> (pdf)

Talks:               >>>

Board Shots:   Initiates file download1  /  Initiates file download2  /  Initiates file download3  /  Initiates file download4  /  Initiates file download5 

Final Report:   Initiates file download>>> (pdf)



Ringberg 2015 is the third of a series of workshops organized at Ringberg under the auspices of the World Climate Research Programmes (WCRP) Opens external link in current windowGrand Science Challenge on Clouds, Circulation and Climate Sensitivity and with the support of the Max Planck Institute for Meteorology in Hamburg, Germany.

Ringberg 2015 revisits the question of Earth's climate sensitivity and its transient response to forcing. Coming on the heels of the fifth assessment report, in which many perceived very little progress to have been made in bounding how Earth responds to forcing, the workshop brings together an international group of experts to look at the different facets of Earth's response to forcing. Through coordinated experiments and a critical assessment of the story lines for a surprisingly large, or small, climate sensitivity the workshop aims to more clearly summarize the current state of understanding as to how Earth responds to forcing, and identify fruitful research directions for further narrowing uncertainty. In so doing a particular focus will be placed on seemingly contradictory lines of evidence, as well as possible early warning signals for a larger or smaller than anticipated climate sensitivity.

The workshop participants are asked to prepare short (10-15 minutes) presentations which will contribute to break-out group discussions on the major themes of the workshop. It would be helpful if these presentations helped us collectively explore reasonable bounds on estimates of climate sensitivities (TCR, ECS), i.e., what we might call extreme sensitivities in the sense that they are "more than likely" not to be exceeded.

I. Is the present range of TCR/ECS too narrow or broad and if so what is the case for changing it?
- physical hypotheses and story lines
- model and observational investigations, underlying mechanisms

II. How would we expect extremely sensitivities (either high or low ones) to physically manifest themselves?
- in terms of climatology, variability, trends and past changes
- in terms of projections

III. How strongly can observations (including palaeo) constrain sensitivities?
- how consistent are different constraints and what can be inferred from multiple constraints?
- do observations suggest models are misoi:10.1175/BAMS-D-13-00sing or distorting key processes?

IV. Outlook
- what are the most promising prospects for reducing uncertainty in estimated ECS/TCR? How to facilitate these?
- any blocking points? Any evidence (or otherwise) that the problem should be addressed differently?
- are there specific ideas or mechanisms to be tested more collectively? Using more exotic models or data?


The workshop will begin on Mondary morning on March 23. Participants can arrive already from 4 pm on Sunday, March 22. The workshop will conclude on Friday, March 27 in the early afternoon, but participants can stay at Ringberg on Friday night, for a departure on the morning of Saturday, March 28 (latest departure after breakfast). Information describing how to get to Ringberg from either Munich main station or the airport is provided here: Initiates file download>>> (pdf). Additional information is also available on the Ringberg website: about travel Opens external link in current windowhere,  about lodging costs Opens external link in current windowhere


Step Volcano Experiment: It has been proposed (by Jonathan Gregory) to carry out a "step volcano" experiment, which he has done with HadCM3, T. Andrews with HadGEM2 and T. Mauritsen (MPI-ESM). We have switched on the 10 times the stratospheric volcanic aerosol of Jan 1992 (about the max of Pinatubo) instantaneously, in order to do an N v T plot to find out the forcing and feedback, as for 4xCO2. Since the forcing is so large, five years is enough, and in our models it becomes non- linear quite quickly, so there's no point in continuing. Anyway, volcanic eruptions do not go on for many years, so only the very beginning of the expt is realistically applicable. Our models show that there is a substantial cloud adjustment reducing the magnitude of the forcing, and the climate sensitivity is smaller (climate feedback parameter larger) than for CO2. This could be relevant to making accurate inferences about GHG climate sensitivity from the historical record, among other things.

For further details contact J. Gregory.


Post AR5 Literature:

Opens external link in current window>>>  Andrews, T. et al., 2015: The dependence of radiative forcing and ... , J. Climate, 28, 1630-1648
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Andrews, T., and M.A. Ringer, 2014: Cloud feedbacks, rapid adjustments, and ... ,  J. Climate, 27, 1799-1818
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Andrews, T., 2014: Using an AGCM to diagnose historical effective radiative ... ,  J. Climate, 27, 1193–1209
Opens external link in current window>>>  Armour, K.C. et al., 2013: Time-varying climate sensitivity from regional feedbacks. J. Climate, 26, 4518-4534
Opens external link in current window>>> 
Bony, S. et al., 2015: Clouds, Circulation and Climate Sensitivity. Nature Geoscience, 261-268 
Initiates file download>>>  Bordbar, M.H. et al., 2015: Effects of long-term variability on projections of ... , NClimate2569
Opens external link in current window>>>  Brient, F. et al., 2015: Shallowness of tropical low clouds as a predictor of ... , Climate Dynamics, submitted
Opens external link in current window>>>  Caldwell, P.M. et al., 2014: Statistical significance of climate sensitivity predictors ... , GRL, 41(5), 1803-1808
Opens external link in current window>>>  Douville, H. et al., 2015: The recent global warming hiatus: What is ... , Geophys. Res. Lett., 42: 880–888.
Opens external link in current window>>>  Feldl, N., and G.H. Roe, 2013: The nonlinear and nonlocal nature of climate feedbacks. J. Climate, 26, 8289-8304
Opens external link in current window>>>  Geoffroy, O., and D. Saint-Martin, 2014: Pattern decomposition of the transient climate response, Tellus A.
Opens external link in current window>>>  Geoffroy, O. et al., 2014: Adjusted radiative forcing and global radiative feedbacks in ... , Climate Dynamics
Initiates file download>>>  Hawkins, E. et al., 2014: The Interpretation and Use of Biases in Decadal Climate Predictions. AMS  
Opens external link in current window>>>  Huber, M. and R. Knutti, 2014: Natural variability, radiative forcing and ... , Nature Geoscience
Opens external link in current window>>>  Huber, M. et al., 2014: Estimating climate sensitivity and future temperature in ... , GRL
Opens external link in current window>>>  Lewis N. and J.A. Curry, 2014: The implications for climate sensitivity of AR5 forcing and ... , Climate Dynamics
Opens external link in current window>>>  Marotzke, J. and P. Forster, 2015: Forcing, feedback and internal variability in global temperature trends. Nature
Opens external link in current window>>>  Meraner, K., et al., 2013: Robust increase in equilibrium climate sensitivity ..., GRL, 40, 5944–5948 
Opens external link in current window>>>  Merlis, T.M., et al., 2014: Constraining transient climate sensitivity using ... , J. Climate, 27, 7781-7795
Initiates file download>>>  Millar, R.J., 2015: Model structure in observational constraints on ... , Climatic Change, in press
Opens external link in current window>>>  Roe G.H., et al., 2015: The remote impacts of climate feedbacks on regional ... , Nature Geoscience, 8, 135–139
Opens external link in current window>>>  Rogelj, J. et al., 2014: Implications of potentially lower climate sensitivity on ... , Environ. Res. Lett.
Opens external link in current window>>>  Rose B.E.J., et al., 2014: The dependence of transient climate sensitivity and ... , GRL, 41
Opens external link in current window>>>  Schaller, N. et al., 2014: The asymmetry of the climate system's response to solar forcing changes and ... , JGR
Opens external link in current window>>>  Sherwood, S. et al., 2015: Adjustments in the forcing-feedback framework for ... , BAMS, in press
Opens external link in current window>>>  Shindell, D. T., 2014: Inhomogeneous forcing and transient climate sensitivity. Nature Climate Change, 4, 274–277
Opens external link in current window>>>  Stevens, B. 2015: Rethinking the lower bound on aerosol radiative forcing. J. Climate, in press
Initiates file download>>>  Storelvmo, T. et al., 2015: Disentangling Greenhouse Warming and Aerosol Cooling to Reveal Earth’s ... , in prep.
Opens external link in current window>>>  Qu, X. et al., 2014: On the spread of changes in marine low cloud cover in ..., Climate Dynamics
             Mauritsen, T. and B. Stevens, 2015: Missing iris-effect as a possible cause of ... , please contact  T. Mauritsen


    >>>  Background material and presentations from the 2014 Ringberg meeting on the Clouds Circulation and
            Climate Sensitivity Grand Science Challenge