“But Modulz”

All about climate models, aka the modulz. The stoopid ones.

See also #ButPredictions, #ButObservations, #ButEvidence.


Maybe people just aren’t buying the decades of failed predictions and wildly inaccurate models anymore.


Interesting. When you use an ML-style method to estimate the effect on climate of CO2 emissions, it comes out fairly small.


Objections and Replies

Clouds. We don’t know if clouds are an important source of warming and
☞ While clouds are complex stuff, Dick & Roy’s claim has fallen into disrepute.

Derivation. I’d like an engineering-quality exposition of sensitivity
There is no direct calculation to accurately prove this.

Discrepancy. Why the huge difference between modulz and observations?
☞ Decadal variability is tough to model. Very noisy. Things are getting better.

Freedom. Don’t impose modulz on us
☞ Nobody does. They’re mostly useful tools to explore the future.

Observation. Should we trust modulz or observations
☞ Unfortunately observations of the future are not available at this time.

Science. Modulz are not science
☞ Have you ever used a thermometer?

Stoopid. Since modulz are stoopid shows that AGW is stoopid too
☞ We don’t need no damn models to support AGW.

Sensitivity. Establishing the true climate sensitivity will save us trillions
The ratio of temperature change to cumulative carbon emissions, is approximately independent of both the atmospheric CO2 concentration and its rate of change on these timescales.

Tweaked. Modulz are tweaked to get the results scientists want—
☞ If only it was that easy, we would not need models in the first place. Many properties emerge from runs. They still need to hindcast properly.

Until. We need better modulz until—
☞ They’re what we got {4}. I’ll keep my eyes open even if hindsight isn’t 20/20.


{} Types of Modulz. Energy models are not climate models are not epidemiological models are not &c.

{} Luckwarm. Arguing sensitivity is as relevant as trying to decide under which conditions plateaux exist. Don’t be suckered in by curiosity, keep the eye on the ball.

{} Spherical cows. All modellers have skeletons of spherical cows in their closets.

{4} You Need One. No model, no measurement. No model, no data. No model, no implementation of any theory whatsoever. Unuseable science.


SSP Database; SSP stands for Shared Socioeconomic Pathways.

2020-01; Modeling Myths of Climate Change; DICE is far from being perfect.

2020-02; But RCPs.

2019-09; Computer Simulation in Science; Eric haz a good entry to the philosophical problems.

2019-02; CMIP6: the next generation of climate models explained.

2018-04; Explainer: How ‘Shared Socioeconomic Pathways’ explore future climate change.

2018-01; How do climate models work?

2018-01; Timeline: The History of Climate Modelling.

2014-08; What Is Business As Usual?; allow NG to explain.

2013-08; Is the climate sensitivity less than 2°C?

Further Readings

2020-10; Variability in historical emissions trends suggests a need for a wide range of global scenarios and regional analyses; https://doi.org/10.1038/s43247-020-00045-y

2020-08; RCP8.5 tracks cumulative CO2 emissions; https://www.pnas.org/content/117/33/19656

2020-07. An Assessment of Earth’s Climate Sensitivity Using Multiple Lines of Evidence. https://doi.org/10.1029/2019RG000678

2019-12; Evaluating the Performance of Past Climate Model Projections; https://doi.org/10.1029/2019GL085378

2019-05; Robust skill of decadal climate predictions; https://doi.org/10.1038/s41612-019-0071-y

2016-09; The Scenario Model Intercomparison Project (ScenarioMIP) for CMIP6; https://doi.org/10.5194/gmd-9-3461-2016

2011-10; Cloud variations and the Earth’s energy budget; https://doi.org/10.1029/2011GL049236

2016-05; Overview of the Coupled Model Intercomparison Project Phase 6 (CMIP6) experimental design and organization; https://doi.org/10.5194/gmd-9-1937-2016.

1988-08; Global climate changes as forecast by Goddard Institute for Space Studies three-dimensional model; https://doi.org/10.1029/JD093iD08p09341.

Climateball Episodes

2018-01; We’re climate researchers and our work was turned into fake news

2011-08; How Scientific Debate Should Be Conducted; Roger Senior and John NG discuss.

2015-05; Lukewarmers – a follow up; genealogy of the luckwarm brand.

Engineerily Deriving; a series of comments on the Auditor’s quest for an “engineer-level formal derivation.”