Teaching Computational Thinking: Examples from Weather and Climate Modeling

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

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RVA

TIO

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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

Contact Us

Teri Eastburneastburn@ucar.edu303.497.1000

Randy Russellrrussell@ucar.edu303.497.1000