Slides from a presentation on climate models held on Aug. 2, 2021 as part of the SMILE teacher workshop at Oregon State University, Corvallis, Oregon.

1. SMILE Workshop, Aug. 2, 2021
Climate
Models
Andreas Schmittner
Oregon State University

2. Textbook
https://open.oregonstate.education/climatechange/

4. Hierarchy of Climate Models
• 0D Energy Balance Model (EBM)
• 1D EBM
• 1D Radiative-Convective Models
• Intermediate Complexity Models (e.g. 2D EBMs)
• 3D General Circulation Models (GCMs)
Increasing
Complexity

5. Climate Models Equations based
on conservation of
• mass
• momentum
• energy
• water
• carbon
• ...
Equations are solved in each of the grid boxes of the model.
Typically global climate models have
about 20-30 layers in the atmosphere
and about the same amount in the
ocean. The horizontal grid box size
varies from about 5 degrees (500 km) to
about 1 degree (100 km) or less.
Models with smaller grid box sizes
r e s o l v e m o r e d e t a i l s ( h i g h e r
resolution), but they are also more
computationally expensive to run.

6. Interactive Components Included
• Atmosphere
• Ocean
• Sea Ice
• Land Surface (sometimes with interactive vegetation)
• Ocean Biology and Chemistry (e.g. Carbon, Nutrient,
and Oxygen Cycles)
• (Ice Sheets, usually prescribed)
Models that include biogeochemistry are also often
called Earth System Models

7. Parameterizations
• Processes that cannot be resolved (smaller than
grid box size need to be expressed in terms of
resolved quantities; often empirical formulas)
• Examples are clouds, convection (atmosphere),
and mixing (ocean)

8. Forcings
• Models are driven by boundary conditions, e.g. incident
solar radiation at the top-of-the-atmosphere, surface
properties (albedo), changes in atmospheric CO2
• Interior is solved without the use of observations

9. Model Evaluation
Models are tested by comparing results to observations.

10. What are climate models used for?
• Paleoclimate Studies
How did climate change in the past and why?
• Detection and Attribution
Is climate changing signi
fi
cantly and if so why?
• Projections
How may climate change in the future?

11. http://www.image.ucar.edu/~nychka/Animations/BTSCAMT340.mp4
http://www.image.ucar.edu/~nychka/talks.html
http://vets.ucar.edu/vg/T341/
High-Resolution Climate Model
1024x512 grid points (30 km)
Water vapor

12. Global Climate Model Grid Box Size ~ 1 degree NS x 1 degree EW

14. Sheehan et al. 2015
Vegetation Type 4 km grid vegetation &
fi
re model
Fire Frequency
West of the Cascades
fi
re frequency increases from ~80 yr recurrence times in 20th century to ~27 yr in 21st century
Coast Range forests shift from
conifer to more
fi
re resistant mixed
forests.
No
fi
re suppression

15. Thank You!