The DOI matches its Crossref record; 11 of the 17 references it cites were found in a registry or an index, and 6 are not checked yet; none of the 9 sources its claims cite is checked for support yet.
Climate model genealogy: Generation CMIP5 and how we got there
Open accessAbstract
A new ensemble of climate models is becoming available and provides the basis for climate change projections. Here, we show a first analysis indicating that the models in the new ensemble agree better with observations than those in older ones and that the poorest models have been eliminated. Most models are strongly tied to their predecessors, and some also exchange ideas and code with other models, thus supporting an earlier hypothesis that the models in the new ensemble are neither independent of each other nor independent of the earlier generation. On the basis of one atmosphere model, we show how statistical methods can identify similarities between model versions and complement process understanding in characterizing how and why a model has changed. We argue that the interdependence of models complicates the interpretation of multimodel ensembles but largely goes unnoticed.
Checked 2026-10-06 · 6 references not checked yet
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The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“and some also exchange ideas and code with other models”
§ Climate model genealogy: Generation CMIP5 and how we got there > Abstract
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIn the paper
“Here, we show a first analysis indicating that the models in the new ensemble agree better with observations than those in older ones”
- Also stated in: § 2. Results · plain
“CMIP5 continues the trend of better agreement with observations [Reichler and Kim, 2008], with the mean distance from observations reduced by approximately 20% from CMIP3 to CMIP5.”
§ Climate model genealogy: Generation CMIP5 and how we got there > Abstract
What the sources say
- Not checked yetcites Reichler and Kim, 2008
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes- Also stated in: § 2. Results · plain
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Most models are strongly tied to their predecessors”
§ Climate model genealogy: Generation CMIP5 and how we got there > Abstract
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“On the basis of one atmosphere model, we show how statistical methods can identify similarities between model versions and complement process understanding in characterizing how and why a model has changed.”
§ Climate model genealogy: Generation CMIP5 and how we got there > Abstract
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesThe paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The distance between models from the same institutions is often a factor of three to ten smaller than that to other models.”
§ Climate model genealogy: Generation CMIP5 and how we got there > 2. Results
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesThe paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“Sharing of model code occurred in CMIP3 (e.g., the Italian INGV model using an ECHAM atmosphere, or the Norwegian BCCR using the French ARPEGE atmosphere also present in CNRM) but has become more widespread in CMIP5.”
§ Climate model genealogy: Generation CMIP5 and how we got there > 2. Results
Strength:plain· not yet calibratedCausal:correlational· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesThe paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The strengths and weaknesses of particular models, as they are evident in the biases in simulating present day climate, are partly passed on to newer model versions and to other models by the exchange of code and ideas.”
§ Climate model genealogy: Generation CMIP5 and how we got there > 3. Conclusion and Discussion
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesA result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The contribution of internal unforced variability (quantified using multiple segments of a control simulation) is small for this metric”
§ Climate model genealogy: Generation CMIP5 and how we got there > 2. Results
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesThe paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“In general, the CAM models with the most similar physics packages cluster closest together.”
§ Climate model genealogy: Generation CMIP5 and how we got there > 2. Results
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesThe paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“The similarity metric is defined from the unperturbed preindustrial model control state and is strongly determined by biases in the present day climatology and seasonal cycle, that is, by model differences rather than initial conditions or forcing.”
§ Climate model genealogy: Generation CMIP5 and how we got there > 2. Results
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passes
- It may state two separate claims as one. 10
- The quote only partly states this claim. 1
- Probably not a substantial claim. 7
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“and that the poorest models have been eliminated”
§ Climate model genealogy: Generation CMIP5 and how we got there > Abstract
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one. The quote only partly states this claim.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“As is clear from the tree shown in Figure 2a, the CAM5 experiments cluster together, with three single perturbation experiments similar to the base CAM5 experiment.”
§ Climate model genealogy: Generation CMIP5 and how we got there > 2. Results
Strength:boosted· not yet calibratedCausal:correlational· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
In the paper
“as shown already by MK11, the different observation and reanalysis data set cluster together (see Figure 1a), and the rankings in Figure 3 are nearly identical irrespective of the chosen data set.”
§ Climate model genealogy: Generation CMIP5 and how we got there > 2. Results
What the sources say
- Not checked yetcites Masson and Knutti, 2011
Strength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
The paper states this without a source or data behind it here, so there is nothing to check it against. The quote shows it is in the paper.
In the paper
“For the projected changes, some models remain close (e.g., those which share a similar atmosphere), whereas other similarities do not persist (e.g., if the new version of a model has a different climate sensitivity).”
§ Climate model genealogy: Generation CMIP5 and how we got there > 2. Results
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The final change in the shallow convection introduces the largest change (last step in panel c), although it brings CAM5 closer to the original CAM4 in some variables (panel b).”
§ Climate model genealogy: Generation CMIP5 and how we got there > 2. Results
Strength:plain· not yet calibratedCausal:direct· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes? Load-bearing: unclear✓ Based: passesIt may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“thus supporting an earlier hypothesis that the models in the new ensemble are neither independent of each other nor independent of the earlier generation”
§ Climate model genealogy: Generation CMIP5 and how we got there > Abstract
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The results point to a remarkable consistency and robustness in many aspects of simulated present day and future climate, but it also suggests that convergence to reality is slow and radical breakthroughs are hard to achieve.”
§ Climate model genealogy: Generation CMIP5 and how we got there > 3. Conclusion and Discussion
Load-bearingStrength:hedged· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Confidence is greatest in those aspects of climate change that we understand and can link back to known physical processes and simpler models and concepts (e.g., the global energy balance).”
§ Climate model genealogy: Generation CMIP5 and how we got there > 3. Conclusion and Discussion
Tests✓ Asserted: passes✗ Checkable: fails✓ Load-bearing: passes✗ Based: failsProbably not a substantial claim. It may be too vague to check against evidence. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“We argue that transparency in the model development process is helpful in understanding model evaluation and projections and contributes to that insight.”
§ Climate model genealogy: Generation CMIP5 and how we got there > 3. Conclusion and Discussion
Tests✓ Asserted: passes✗ Checkable: fails✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim. It may be too vague to check against evidence.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Note that all results presented here are only based on model output; they assume no knowledge about the structure, parameterizations, or code of any model.”
§ Climate model genealogy: Generation CMIP5 and how we got there > 2. Results
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim. It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“None of those choices affect the main conclusions.”
§ Climate model genealogy: Generation CMIP5 and how we got there > 2. Results
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✗ Based: failsProbably not a substantial claim. The paper may give no reason why it holds.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Confidence in model projections does not come from the sheer amount of code and data and cannot be demonstrated by repeated verification.”
§ Climate model genealogy: Generation CMIP5 and how we got there > 3. Conclusion and Discussion
Load-bearingStrength:plain· not yet calibratedTests✓ Asserted: passes✗ Checkable: fails✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim. It may be too vague to check against evidence. It may state two separate claims as one.
In the paper
“but with the strong caveat that linking model performance metrics to model quality or skill is difficult, subjective, and strongly metric dependent [Gleckler et al., 2008]”
§ Climate model genealogy: Generation CMIP5 and how we got there > 2. Results
What the sources say
- Not checked yetcites Gleckler et al., 2008
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesIt may state two separate claims as one.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“We propose that one reason some models are so similar is because they share common code.”
§ Climate model genealogy: Generation CMIP5 and how we got there > 3. Conclusion and Discussion
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✗ Based: failsProbably not a substantial claim. The paper may give no reason why it holds.
In the paper
“MK11 argued that such similarities result from the fact that models evolve from their ancestors by modification and by exchange of ideas and code with other groups.”
§ Climate model genealogy: Generation CMIP5 and how we got there > 1. Introduction
What the sources say
- Not checked yetcites Masson and Knutti, 2011
Tests✓ Asserted: passes✓ Checkable: passes✓ Load-bearing: passes✓ Based: passesProbably not a substantial claim.
The authors state this as an assumption.
The models in an ensemble are approximately a representative sample of uncertainty in how to best describe the climate system given limited observations, imperfect understanding, and finite computational resources.
“This assumes that the models are approximately a representative sample of our uncertainty in how to best describe the climate system given limited observations, imperfect understanding, and finite computational resources [Knutti, 2008;Yokohata et al., 2012].”
The authors state this as an assumption.
There are not too many similarities among models that would bias the results of an ensemble.
“It also assumes that there are not too many similarities that would bias the results.”
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
In the citing paper
“Since CMIP5 projections are an incremental advance over CMIP3 data [34–36], this does not limit the relevance of our analysis as a tool for assessing anthropogenic influences on future fire activity.”
From Incorporating Anthropogenic Influences into Fire Probability Models: Effects of Human Activity and Climate Change on Fire Activity in California (2016) · cites this paper as [34]
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
Each contradiction between two passages listed here was confirmed by an independent check.
Overall distance metric is described two different ways
MinorThe methods section says the combined temperature-precipitation distance used for Figure 3 is a mean square, while the Figure 3 caption calls it a root mean square. Taking the square root changes the reported distance values.
“for Figures 1 and 3, the metric now also includes differences in the annual mean climatology and that we use the mean square of the temperature and precipitation distance to define overall similarity”
“The distance metric is calculated as the root mean square of the surface temperature and precipitation distance as in Figure 1”
Citations
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Climate change 2007: the physical science basis
Solomon, S., Qin, D., Manning, M., Marquis, M. C., Averyt, K. B., Tignor, M., Miller, H. L., & Chen, Z. (2007) · Cited by 23,398
An Overview of CMIP5 and the Experiment Design
Taylor, K. E., Stouffer, R. J., & Meehl, G. A. (2012) · Bulletin of the American Meteorological Society · doi:10.1175/bams-d-11-00094.1 · Cited by 14,052
The use of the multi-model ensemble in probabilistic climate projections
Tebaldi, C., & Knutti, R. (2007) · Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences · doi:10.1098/rsta.2007.2076 · Cited by 1,862
Self-citationRobustness and uncertainties in the new CMIP5 climate model projections
Knutti, R., & Sedláček, J. (2013) · Nature Climate Change · doi:10.1038/nclimate1716 · Cited by 1,569
Self-citationPerformance metrics for climate models.
Gleckler, P. J., Taylor, K. E., & Doutriaux, C. (2008) · Journal of Geophysical Research: Atmospheres · doi:10.1029/2007jd008972 · Cited by 1,328
Challenges in combining projections from multiple climate models.
Knutti, R., Furrer, R., Tebaldi, C., Cermak, J., & Meehl, G. A. (2010) · Journal of Climate · doi:10.1175/2009jcli3361.1 · Cited by 1,270
Self-citationA numerical method for the study of the circulation of the world ocean
Bryan, K. (1969) · Journal of Computational Physics · doi:10.1016/0021-9991(69)90004-7 · Cited by 974
A Numerical Method for the Study of the Circulation of the World Ocean
Bryan, K. (1997) · Journal of Computational Physics · doi:10.1006/jcph.1997.5699 · Cited by 906
How Well Do Coupled Models Simulate Today's Climate?
Reichler, T. J., & Kim, J. (2008) · Bulletin of the American Meteorological Society · doi:10.1175/bams-89-3-303 · Cited by 880
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Metadata
- Authors
- Knutti, R., Masson, D., & Gettelman, A.
- Affiliations
- ETH Zurich (CH)
- Federal Office of Meteorology and Climatology MeteoSwiss (CH)
- NSF National Center for Atmospheric Research (US)
- Corresponding author
- Knutti, Reto
- Venue
- Geophysical Research Letters
- Publisher
- American Geophysical Union (AGU)
- Published
- 2013-03-26
- Volume
- 40
- Issue
- 6
- Pages
- 1194-1199
- ISSN
- 0094-8276 (ISSN-L)
- 1944-8007
- OpenAlex
- W1796961055
- Semantic Scholar
- f6507ca951e61214c9268ce9a43376724b2f9bcf
- Cited by
- 918
- References
- 17
- Citations by year
- 2026: 37 · 2025: 42 · 2024: 54 · 2023: 73 · 2022: 114 · 2021: 126 · 2020: 109 · 2019: 64 · 2018: 76 · 2017: 67 · 2016: 51 · 2015: 55 · 2014: 42 · 2013: 7
- FWCI
- 39.41
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Geophysical Research Letters (publishedVersion)
- Repository for Publications and Research Data (ETH Zurich) (submittedVersion, other-oa)
- ETH Zürich Research Collection
- Topics
- Physical Sciences › Environmental Science › Global and Planetary Change › Climate variability and models
- Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Meteorological Phenomena and Simulations
- Social Sciences › Economics, Econometrics and Finance › Economics and Econometrics › Climate Change Policy and Economics
- Keywords
- CMIP5, multi-model ensemble, model validation against observations, climate change projections, statistical model comparison
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