Ringberg 2015

WCRP Grand Challenge Workshop: Earth's Climate Sensitivities

March 23-27, 2015

Schloss Ringberg
3700 Rottach-Egern, Germany

Conveners:   

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

Participants:   >>> (pdf)
Agenda:          >>> (pdf)

Talks:               >>>

Board Shots:   1  /  2  /  3  /  4  /  5 

Final Report:   >>> (pdf)

Overview:

Ringberg 2015 is the third of a series of workshops organized at Ringberg under the auspices of the World Climate Research Programmes (WCRP) Grand 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.

Programme:
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?

Logistics:

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: >>> (pdf). Additional information is also available on the Ringberg website: about travel here,  about lodging costs here

Experiments:

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:

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