Summary: Climate models are important for several reasons. Large flows of tax dollars go to their construction and operation. Their predictions dominate the public policy debate about climate change (to the exclusion of other tools, such as predictability studies). In this post eminent climate scientist Roger Pielke Sr. explains that long-term model forecasts have shown little skill at forecasting. Post your questions in the comments; he’ll answer as time permits. {1st of 2 posts today).
“I offer a toast to the future, the undiscovered country.”
— Klingon Chancellor Gorkon in “Star Trek VI: The Undiscovered Country
The undiscovered country from whose bourn no traveler returns, puzzles the will and makes us rather bear those ills we have than fly to others that we know not of? …And thus the native hue of resolution is sicklied o’er with the pale cast of thought, and enterprises of great pith and moment with this regard their currents turn awry, and lose the name of action. {Hamlet}
How accurately do the global climate models simulate the real climate?
Guest post by Roger A. Pielke Sr.
The climate models are useful as sensitivity experiments but using them to claim an ability to skillfully project climate, even on the global scale, in the coming decades has not been shown.
The new seminal Stephens et al paper provides a clear documentation of the level of model skill: “The albedo of Earth” in Reviews of Geophysics, March 2015. There is also a power point talk on this: “Is the Earth’s climatesystem constrained?” Among their conclusions is that …
“Climate models fail to reproduce the observed annual cycle in all components of the albedo with any realism, although they broadly capture the correct proportions of surface and atmospheric contributions to the TOA {top of atmosphere} albedo. A high model bias of albedo has also persisted since the time of CMIP3, mostly during the boreal summer season. Perhaps more importantly, models fail to produce the same degree of interannual constraint on the albedo variability nor do they reproduce the same degree of hemispheric symmetry.”
The technical term albedo “is the fraction of solar energy (shortwave radiation) reflected from the Earth back into space. It is a measure of the reflectivity of the earth’s surface. Ice, especially with snow on top of it, has a high albedo: most sunlight hitting the surface bounces back towards space” (From the Earth & Space Research website). CMIP3 is phase 3 of the Coupled Model Intercomparison Project (CMIP) of the World Climate Research Programme (WCRP). They collect the output of global climate models (i.e., coupled atmosphere-ocean general circulation models).
Stephens et al further bolsters the conclusions we summarized in the preface to Climate Vulnerability: Understanding and Addressing Threats to Essential Resources (5 volumes, 2013)…
“…for decadal and multidecadal predictions little, if any, predictive skill has been shown in hindcast climate model predictions of changes in regional weather statistics beyond what is available to the impacts community via the historical, recent paleorecord and a worst case sequence of weather events.”
This conclusion is similar to that in “Regional climate downscaling – what’s the point?” by R. A. Pielke Sr. and R.L. Wilby in Eos Forum, 31 January 2012.
What does the IPCC say?
In AR5, there are two chapters about models’ skill. Chapter 11 discusses “decadal predictability”: “Near-term Climate Change: Projections and Predictability“. Chapter 12 examines “Long-term Climate Change: Projections, Commitments and Irreversibility“.
I view the distinction as key, as the “projection” chapter assumes that just the forcings (CO2, etc.) dominate on time periods longer than a decade. They base this on comparisons of model runs with and without those forcings; not with tests on their skill and replicating observed real-world multi-decadal global and regional climate patterns.
Post your questions and comments
Please post your questions in the comments. Comments with evidence that refutes this conclusion are invited. Please keep them brief (i.e., no essays), and respond with a direct quote where possible to keep the conversation clear. This is a technical thread; please avoid comments about life, politics, and personalities.
See the follow-up post: Thomas Kuhn & Twitter tell us what we need to know about climate science.
About the author
Roger Pielke Sr. is currently a Senior Research Scientist in Cooperative Institute for Research in Environmental Science. He is also an Emeritus Professor of Atmospheric Science at Colorado State University, and now serves there as a Senior Research Associate.
His list of accomplishments, honors, and publications is too long to list here. See his bio for details. See his website for commentary on climate science issues. Also see his presentations, especially these…
- Roger Pielke Sr.’s testimony to the Science, Space, and Technology Committee on 29 May 2014.
- “Climate Threats: A More Inclusive Assessment Is Needed“. A look at peer-reviewed papers of hindcast multi-year climate model prediction skill (2015).
Editor’s suggestions: articles for laypeople about this vital subject
These provide an introduction to the subject, and a deeper review of this frontier in climate science.
- “A Model World” by Jon Turney in Aeon, 16 December 2013.
- “Climate Modeling 101: What are climate models and why are they important?” by the National Academy of Science.
- An introduction to climate models by the World Meteorological Society.
- “The Physics of Climate Modeling” by Gavin A. Schmidt in Physics Today, January 2007.
Judith Curry (Prof Atmospheric Science, GA Inst Tech) reviews the literature about the uses and limitation of climate models…
- What can we learn from climate models?
- Philosophical reflections on climate model projections.
- Spinning the climate model – observation comparison — Part I.
- Spinning the climate model – observation comparison: Part II.
For More Information
To learn more about the state of climate change see The Rightful Place of Science: Disasters and Climate Change
If you liked this post, like us on Facebook and follow us on Twitter. For more information see The keys to understanding climate change and My posts about climate change. Also, see these posts about computer models, especially these..
- About models, increasingly often the lens through which we see the world.
- Will a return of rising temperatures validate the IPCC’s climate models?
- We must rely on forecasts by computer models. Are they reliable?
- A frontier of climate science: the model-temperature divergence.
A sample of the large body of research about this topic
- “The Robustness of the Climate Modelling Paradigm“, A. M. R. Bakker, Jan 2015.
- “Overestimated global warming over the past 20 years” by John C. Fyfe et al, Nature Climate Change, Sept 2013.
- Preface to Climate Vulnerability, Understanding and Addressing Threats to Essential Resources, R. A. Pielke Sr., Editor in Chief, (2013).
- “Comments on “The North American Regional Climate Change Assessment Program: Overview of Phase I Results” by R. A. Pielke Sr. in Bulletin of the. American Meteorological Society, July 2013.
- “Regional climate downscaling – what’s the point?” by R. A. Pielke Sr. & R.L. Wilby in Eos Forum, 31 Jan 2012.
- “Dealing with complexity and extreme events using a bottom-up, resource-based vulnerability perspective. Extreme Events and Natural Hazards: The Complexity Perspective“, Pielke Sr. et al, in the Geophysical Monograph Series 196 of the American Geophysical Union (2012).
- “Should we assess climate model predictions in light of severe tests?” by Joel Katzav in Eros, 7 June 2011.
- “Should we believe model predictions of future climate change?” by Reto Knutti in Philosophical Transactions A, Dec 2008.
- “Contrast between predictive and vulnerability approaches” by R. A. Pielke Sr. & T.J. Stohlgren in Chapter E.3 of Vegetation, Water, Humans and the Climate: A New Perspective on an Interactive Systeme, P. Kabat et al., Editors, (2004).
- “Conclusions” by R. A. Pielke Sr. & L. Bravo de Guenni in Chapter E.7 in Vegetation, Water, Humans and the Climate: A New Perspective on an Interactive System, P. Kabat et al., Editors, (2004).
