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Teaching Computational Thinking: Examples from Weather and Climate Modeling. “Essentially, all models are wrong, but some models are useful.” - George E. P. Box (1951). Teresa Eastburn & Randy Russell National Center for Atmospheric Research University Corporation for Atmospheric Research. - PowerPoint PPT Presentation
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Teaching Computational Thinking: Examples from Weather and Climate
Modeling“Essentially, all models are wrong,but some models are useful.”
- George E. P. Box (1951)Teresa Eastburn & Randy RussellNational Center for Atmospheric ResearchUniversity Corporation for Atmospheric Research
NSTA Denver, December 12, 2013
Computational Thinking Solving problems, designing systems, and
understanding human behavior by drawing on the concepts fundamental to computer science.
~ Jeannette Wing, Carnegie Mellon
Integrating the power of human thinking with the capabilities of computers. ~CSTA
Steven GilbertNSTA Press
1. What is a climate model, why are supercomputers needed, and what do they do and not do?2. The Systems Game – Why systems thinking matters3. What’s the difference between a weather model vs a climate model (initial value problem vs. a boundary value problem)?4. Chaos Theory5. Climate simulations for your you and your students to explore
Here’s What We’ll Be Covering
Spark – science education at NCAR
National Center for Atmospheric Researchin Boulder
NCAR Mesa Lab in Boulder
Public and School Group Visits
spark.ucar.edu/visit
spark.ucar.edu/workshops
spark.ucar.edu/events/workshop-computational-thinking-nsta-regional-2013
Evolution of Climate Models
Credit: Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4): Working Group 1: Chapter 1, page 99, Fig. 1.2
Climate Model Components
Credit: UCAR (Paul Grabhorn)
Climate Model Components
Credit: UCAR
• Observations• Theory• Numerical Modeling
Progress in climate models occurs as a result of:
Like a sturdy 3-legged stool
OB
SE
RVA
TIO
N
THE
OR
Y MO
DE
LING
“Science presumes that things and events
in the Universe occur in consistent patterns
that are comprehensible through careful,
systematic study.” ~ AAAS
Models are today’s tech test tube for the Earth system.
Image sourceadaption:NOAA
Images adapted from K. Dickson, NOAA
Climate Models = Virtual Earth• Now we can model various components
(parts or subsystems) in the Earth system (atmosphere, ocean, sea ice, land physics…) and how they will interact and respond over time to a natural or human-made forcing agent.
Atmosphere Circulation & Radiation
Sea Ice
Ocean Circulation
Land Physics
Resolution: What Does It Mean?
Improving Resolution of Climate Models
Credit: Warren Washington, NCAR
Grid Cell Sizes• 1990s (T42)
• 200 x 300 km• 120 x 180 miles
• 2000s (T85)• 100 x 150 km• 60 x 90 miles
Improving Resolution of Climate Models
Credit: Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4): Working Group 1: Chapter 1, page 113, Fig. 1.4
Vertical Resolution of Climate Models
Vertical Layers• 1990s
• 10 layer atmosphere• 1 layer “slab” ocean
• 2000s• 30 layer atmosphere• 30 layer ocean
Credit: UCAR
Horizontal and Vertical Grid
Horizontal and Vertical Grid
Hexagonal Grid and Sub-grids
Credit: UCAR (Lisa Gardiner)
spark.ucar.edu/sites/default/files/SystemInMotionMaster.pdf
Using Models in Education
“Essentially, all models are wrong,but some models are useful.”
- George E. P. Box (1951)
Weather vs Climate ProjectionsPhysics is Physics, Right?
Why do we think we can make meaningful 100 year climate projections when we can’t forecast the day-to-day weather a month from now? Initial Value Problem vs Boundary Value Problem
Weather Model vs Climate ModelCompare and Contrast
Differences (and similarities) betweenWeather vs. Climate Models
• Area Covered (scale)• Resolution – distance (spatial) and time (temporal)
• Timespan covered by model runs• Impacts on computing resources needed, time required to run models
Weather Model vs Climate ModelArea Covered
Weather Model – up to about continental size scale Climate Model – global size
scale
Larger area requires either more computing power/time or lower resolution (spatial and/or temporal)
Weather Model vs Climate ModelResolution and Precision
Weather Model• resolution typically about 3-10 km• timesteps of hourly to 6 hours, forecast for next 3-4 days
Climate Models• resolutions from about 25-30 km up to 100 (or a couple
hundred) km• running computer models can take days or weeks, which
would be impractical for weather models
Precision – why Wx forecast for Christmas is suspect, but temperature next July is reliable (relationship to chaos)
Weather Model vs Climate Model
Timeframe
Weather Forecast – hours to days(up to about 10 days)
Climate Projection – decades to centuries or longer(climate is usually defined as at least 30 years of observations)
Resolution: Spatial & Temporal (Time)• Timesteps can be a few minutes to 12 hours or
more• Durations can be hours to centuries
Resolution and Computing Power Double resolution – increase number of nodes – more
calculations! One Dimension
Two Dimensions
2 times as many nodes
4 times as many nodes
Resolution and Computing PowerWhat if we increase model to three dimensions (space) plus time?
Resolution and Computing PowerWhat if we increase model to three dimensions (space) plus time?
16 times as many nodes – 16x computing power required!
This is why we need supercomputers!
Chaos• Chaos – 10-day forecast reliability limit• Ensemble runs of models – tipping points –
arctic ice melt – sea ice and open water albedo images
• Why Wx forecast for Xmas is suspect, but temperature next July is reliable (relationship to chaos)
Climate Forcings
Source: Meehl et al NCAR
Which of the following cannot be addressed by a physical climate model?
1. How would Earth’s average surface temperature be expected to change if carbon dioxide doubled?
2. How much carbon dioxide and methane will humans add to the atmosphere during each of the next five decades?
3. Can cosmic rays from the sun affect clouds and hence play an important role in climate variability and change?
4. Is it possible to learn about past climate variations by gathering data from holes drilled deep into the Earth’s crust?
5. All above can be addressed by physical climate science.
F = P x g x e x f x d• F = total GHG emission rate• P = population size (global and/or national)• g = per capita gross world/domestic capital• e = energy use per $ of gross world/national
product• f = GHG emissions per unit energy use• d = deforestation effects
How will GHG vary?
Ensemble Projections of Global Temperature for Various Emission
Scenarios
Source: UCAR/NCAR
FutureProjections
VersesForecasts
Climate Models help with…
DETECTION - Is the planet’s climate changing significantly?
ATTRIBUTION – If so, what is causing the change?Nature? Human Actions? Both?
PROJECTION – What does the future hold for Earth’s climate?
Models in the Standards
Next Generation Science Standards
Greenhouse Effect Review
CO2 absorbs heat in the atmosphere
When heat accumulates in the Earth system, the average global temperature rises
Increased CO2 & the Greenhouse Effect When the amount of carbon dioxide in the atmosphere
increases, average global temperature rises. Longwave radiation emitted by CO2 is absorbed by the
surface, so average global temperature rises
Emissions -> More CO2 in Air -> Higher Temperature
15°
18°
Climate Sensitivity - definitionWhenever the amount of carbon dioxide in the
atmosphere doubles, average global temperature rises by 3 degrees Celsius.
15°
18°
15°
18°
Learning from the Past (ice cores)
Ice ageIce ageIce ageIce age
CO2 Emissions – Where are we now?
In 2013, CO2 emissions are around 10 gigatons (GtC) per year (10,000 million tons in units used on this graph)
CO2 in Atmosphere – Where are we now?
iceage
iceage ice
ageiceage
396 ppm in 2013 For hundreds of thousands of
years, CO2 varied between 180 and 280 parts per million, beating in time with ice ages
Since the Industrial Revolution, CO2 has risen very rapidly to about 400 ppm today
Math of Climate SensitivityWhen the CO2 concentration in the atmosphere doubles,temperature rises by 3°Celsius (about 5.4°F)
Examples: If CO2 rises from 200 ppmv to 400 ppmv,
temperature rises 3°C If CO2 rises from 400 ppmv to 800
ppmv, temperature rises 3°C Note: as CO2 rises from 200 to 800
ppmv (800 = 4 x 200), temperature rises 6°C ( = 2 x 3 degrees, not 4 x 3 degrees)
Climate Sensitivity Calculator demo
spark.ucar.edu/climate-sensitivity-calculator
Climate Sensitivity Calculator Activity
Use the calculator (previous slide) to determine the expected temperature for the various CO2 concentrations listed in column 1 of the table above (students fill in column 2); then have them graph.
Advanced Climate Sensitivity Math
T = T0 + S log2 (C / C0)T : new/current temperatureT0 : reference temperature (e.g. 13.7 degrees C in 1820)S : climate Sensitivity (3 degrees C)C : new/current atmospheric CO2 concentrationC0 : reference atmospheric CO2 concentration (e.g. 280 ppmv in 1820)Example:What is new temperature if CO2 rises to 400 ppmv (from 280 ppmv)?T = T0 + S log2 (C / C0) = 13.7 + 3 log2 (400/280) = 13.7 + 3 log2 1.43 = 13.7 + 1.54 = 15.2 degrees C
Dry air mass of atmosphere = 5.135 x 1018 kg = 5,135,000 GigatonsCO2 currently about 599 ppm by mass (395 ppmv) = 0.0599%CO2 current mass = 0.0599% x 5,135,000 Gt = 3,076 GtCO2 current emissions = 9.5 GtC/yearAtmospheric fraction = 45%
M = M0 + [0.45 x (3.67 x m)] = 3,076 GtCO2 + [0.45 x (3.67 x 9.5 GtC/yr)] = 3,076 + 15.7 GtCO2 = 3,092 GtCO2
CO2 concentration = 3,092/5,135,000 = 602 ppm by massCO2 concentration = (602/599) x 395 ppmv = 397 ppmv
Math of CO2 Emissions andAtmospheric Concentration
(16 + 12 + 16) / 12
= 44/12 = 3.67
GtC vs GtCO2
Poll: Rising Emissions
B
A
C
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Poll: Rising Emissions
B
A
C
?
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B
A
C
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Poll: Emissions rise then steady
B
A
C
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Poll: Emissions rise then fall
Very Simple Climate Model demo
spark.ucar.edu/simple-climate-model
Why does temperature continue to rise as emission rate declines?
Atmosphere
CO2 in Atmosphere
CO2
Emissions
CO2 Removal byOceans & Plants
spark.ucar.edu/climate-bathtub-model-animations-flow-rate-rises-fallsspark.ucar.edu/imagecontent/carbon-cycle-diagram-doe