Comments On The PNAS Article “Expert Judgments About Transient Climate Response To Alternative Future Trajectories Of Radiative Forcing” By Zickfeld Et Al

Thanks to Marcel Crok for alerting us to this article

Kirsten Zickfeld, M. Granger Morgan, David J. Frame, and David W. Keith, 2010: Expert judgments about transient climate response to alternative future trajectories of radiative forcing. Proceedings of the National Academy. Published online before print June 28, 2010, doi: 10.1073/pnas.0908906107

The abstract reads

“There is uncertainty about the response of the climate system to future trajectories of radiative forcing. To quantify this uncertainty we conducted face-to-face interviews with 14 leading climate scientists, using formal methods of expert elicitation. We structured the interviews around three scenarios of radiative forcing stabilizing at different levels. All experts ranked “cloud radiative feedbacks” as contributing most to their uncertainty about future global mean temperature change, irrespective of the specified level of radiative forcing. The experts disagreed about the relative contribution of other physical processes to their uncertainty about future temperature change. For a forcing trajectory that stabilized at 7 Wm-2 in 2200, 13 of the 14 experts judged the probability that the climate system would undergo, or be irrevocably committed to, a “basic state change” as ≥0.5. The width and median values of the probability distributions elicited from the different experts for future global mean temperature change under the specified forcing trajectories vary considerably. Even for a moderate increase in forcing by the year 2050, the medians of the elicited distributions of temperature change relative to 2000 range from 0.8–1.8 °C, and some of the interquartile ranges do not overlap. Ten of the 14 experts estimated that the probability that equilibrium climate sensitivity exceeds 4.5 °C is > 0.17, our interpretation of the upper limit of the “likely” range given by the Intergovernmental Panel on Climate Change. Finally, most experts anticipated that over the next 20 years research will be able to achieve only modest reductions in their degree of uncertainty.”

Here are the names of the experts that were used. 

Allen, M. University of Oxford, Oxford, UK
Collins, M. Hadley Centre for Climate Prediction and Research,
Exeter, UK
Flato, G. Canadian Centre for Climate Modelling and Analysis,
Victoria, BC, Canada
Forest, C. Massachusetts Institute of Technology, Cambridge,
MA, USA
Karl, T. National Climatic Data Center, Asheville, NC, USA
Knutti, R. National Center for Atmospheric Research, Boulder,
CO, USA
Rahmstorf, S. Potsdam Institute for Climate Impact Research,
Potsdam, Germany
Schlesinger, M. University of Illinois, Urbana-Champaign, IL, USA
Schneider, S.H. Stanford University, Palo Alto, CA, USA
Senior, C. Hadley Centre for Climate Prediction and Research,
Exeter, UK
Stainforth, D. University of Oxford, Oxford, UK
Stone, P. Massachusetts Institute of Technology, Cambridge,
MA, USA
Weaver, A.J. University of Victoria, Victoria, BC, Canada
Wigley, T. National Center for Atmospheric Research, Boulder,Colorado, USA

What is interesting about this article from strong proponets of the IPCC perspective on climate science, is their conclusion , as summarized in the abstract that

“….most experts anticipated that over the next 20 years research will be able to achieve only modest reductions in their degree of uncertainty.”

Thus what is expected from the millions of dollars being spent apply global models to predict regional weather patterns and climate impacts decades from now? This is a major reason we have urged the adoption of  bottom-up, resource-based vulnerability assessments of food, energy, water, human health, and ecosystem function, as a complement to prediction, as we concluded in our paper

Pielke Sr., R., K. Beven, G. Brasseur, J. Calvert, M. Chahine, R. Dickerson, D. Entekhabi, E. Foufoula-Georgiou, H. Gupta, V. Gupta, W. Krajewski, E. Philip Krider, W. K.M. Lau, J. McDonnell,  W. Rossow,  J. Schaake, J. Smith, S. Sorooshian,  and E. Wood, 2009: Climate change: The need to consider human forcings besides greenhouse gases. Eos, Vol. 90, No. 45, 10 November 2009, 413. Copyright (2009) American Geophysical Union

where we wrote

We therefore propose that one should not rely solely on prediction as the primary policy approach to assess the potential impact of future regional and global climate variability and change. Instead, we suggest that integrated assessments within the framework of vulnerability, with an emphasis on risk assessment and disaster prevention, offer a complementary approach [Kabat et al., 2004]. This should be conducted in parallel with attempts to improve skill in predicting regional and global climate on multidecadal time scales. This leads to a practical and sensible way forward that will permit a more effective climate policy by focusing on the assessment of adaptation and mitigation strategies that can reduce the vulnerability of all of our important societal and environmental resources (involving water, food, energy, and human and ecosystem health) to both natural and human- caused climate variability and change.

With the vulnerability approach, if the improvements in prediction skill is as pessimistic as concluded by the individuals contacted in the Zickfeld et al 201o survey, then policymakers will still have a robust set of information for effective policy actions.

Comments Off on Comments On The PNAS Article “Expert Judgments About Transient Climate Response To Alternative Future Trajectories Of Radiative Forcing” By Zickfeld Et Al

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