GLOBE Carbon Cycle: Modeling

University of New Hampshire: Rita Freuder, Lara Gengarelly, Mary Martin, Scott Ollinger, Annette Schloss, Sarah Silverberg

Czech Republic: Jana Albrechtova, Kateřina Čiháková, Zuzana Lhotakova, Barbora Semeráková, Premek Stych, Dana Votapkova  

GLOBE Program Office: Gary Randolph

The American Heritage® Dictionary of the English Language, Fourth Edition

*mod·el  (n). 1. A small object, usually built to scale, that represents in detail

another, often larger object.

2. A preliminary work or construction that serves as a plan from which a final product is to be made.

3. A schematic description of a system or phenomenon that accounts for its known or inferred properties and may be used for further study of its characteristics.

4. One that serves as the subject for an artist, especially a person employed to pose for a painter, sculptor, or photographer.

5. A person employed to display merchandise, such as clothing or cosmetics.

What is a Model?

Models are tools and concepts that help us Models are tools and concepts that help us understand, explain, and predict systems that are understand, explain, and predict systems that are too complex or difficult to observe, or to too complex or difficult to observe, or to

comprehend on our own.comprehend on our own.

----

Models are simplifications of reality.Models are simplifications of reality. ----

““The most useless scale for a The most useless scale for a road map is 1:1”road map is 1:1”

Better Working Definitions

• Synthesize existing knowledge in ways not possible using human CPU (Cranial Processing Unit).

• Forecast future conditions, often with policy- relevant goals.

• Examine the fundamental behavior of a system.

• Identify gaps in current knowledge and to guide future research.

• Generate hypotheses (as opposed to predictions).

““The purpose of models is not to fit the data but to The purpose of models is not to fit the data but to sharpen the questions”. -S. Karlinsharpen the questions”. -S. Karlin

Why Use a Model?

A “Box and Arrow” or “Pool and Flux” modelA “Box and Arrow” or “Pool and Flux” model

STANDING STOCK (Pool, Reservoir)(Pool, Reservoir)

INPUTS OUTPUTS

FluxFlux FluxFlux

Models Don’t Need to be Complex to be Useful

Residence Time: the amount of time material remains in a pool

Turnover Rate: the fraction of material in a pool that enters or leaves in a specified amount of time

MODELING TERMS•Pool/reservoir/stock

•A space to store a substance, or a supply of a substance

•Flux/flow/transfer/throughput•The rate of flow of some quantity (such as water, energy or carbon) from one place or reservoir to another

•Inflow/Input•Matter, energy or information entering a system

•Outflow/Output•Matter, energy or information leaving a system

•Residence time•The average length of time a substance spends in a given reservoir that is at a steady state with respect to the processes that add and remove the substance to and from the reservoir. Residence time is calculated as the ratio of the reservoir size to the rate of inflow or outflow (which are equal at steady state).

•Turnover rate•The fraction of material in a component that enters or leaves in a specified time interval

•Steady state/equilibrium•A condition in which the state of a system component is unchanging in time. A reservoir is in steady state when the rates of inflow and outflow are equal.

Questions for Students to Answer

Models can help answer many types of questions…

• What is the amount of C storage on our school site?

• Is our school site a sink or source of C to the atmosphere?

• How would the global carbon cycle be affected by (examples):

• Soil respiration increases due to permafrost melting?

• A change in human CO2 emissions?

• Reduction in deforestation in tropical forests?

• An increase in global air pollution? (ozone, sulfur, etc.)

Modeling Themes: found in the standards

• Models as tools

• Scales - time, size, numbers

• Systems - How do systems work?, Connecting system parts

• Cycling in the Earth system

• Understand how human actions…

iSee Systems

http://www.iseesystems.com/

iSee Systems – isee player

iSee Systems – STELLA Trial

iSee Systems - STELLA

iSee Systems – STELLA Tutorials

iSee Systems – Sample Models

iSee Player Tutorial

• Step by step instructions for how to use the isee player

• Meant for first time users and as a refresher

• Uses the 1 box forest biomass model as the example

• Currently available as a presentation or printable pdf

STANDING STOCK (Pool)(Pool)

Forest Biomass

INPUTS (Wood Growth)

OUTPUTS (Mortality +

Woody Litter)FluxFlux

FluxFlux

~400 g/m2 * yr ~2% / year

1 Box Forest Biomass Model

OUTPUT = (?)

2% per year

(Current Biomass * 0.02)

• Remember 50% of biomass by weight is carbon!!!

1 Box Forest Biomass Model

0

10000

20000

30000

0 50 100 150 200 250 300 350 400

Year

Bio

mas

s (g

/m2)

1 Box Forest Biomass Model

1 Box Forest Biomass ModelWoodBiomass(t) = WoodBiomass(t - dt) + (WoodNPP - WoodLitter - Harvest) * dtINIT WoodBiomass = 0

INFLOWS:WoodNPP = 3.9 + 200*Foliar_Nitrogen

OUTFLOWS:WoodLitter = WoodBiomass * WoodLossHarvest = IF (TIME = HarvYear) then (WoodBiomass * HarvIntens) ELSE (0)BiomassIncrement = WoodNPP - WoodLitter Foliar_Nitrogen = 2HarvIntens = 0HarvYear = 0WoodLoss = .02

1 Box Forest Biomass Model - Activities

• Basic questions: Students learn to read model output graphs and tables.

• Changing 1 variable at a time: Students make connections between model inputs and their effect on model outputs.

• Working with 2 variables: Students develop and understanding of the science in the model.

• Thought questions: Students will understand forest biomass and can relate it to carbon storage.

• Scenarios: Students create model scenarios based on scientific ideas and previous questions for other students to work through.

Global Carbon Model

Global Carbon Model - Activities

• Activities to come soon…

• What questions do students ask?

• What do you want to use the model to explore?

• What are current issues around climate change that the model could address?