By Caroline Brennan & Elizabeth Elbel. Idealized Energy Balance on Earth.
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Transcript of By Caroline Brennan & Elizabeth Elbel. Idealized Energy Balance on Earth.
By Caroline Brennan & Elizabeth Elbel
Idealized Energy Balance on Earth
Key Aspects of ModelingKey Aspects of ModelingPurposePurpose
To produce climate projections for anticipated changes in the system.
Identify the components of the system Identify the components of the system What entities are moving through the system?What entities are moving through the system?What processes are involved in moving the What processes are involved in moving the
entity entity through the system?through the system?What kinds of things do these processes depend What kinds of things do these processes depend
on on complete their actions?complete their actions?
Define and consider if conditions could Define and consider if conditions could exist in the real worldexist in the real world
Intro to Climate System ModelingIntro to Climate System ModelingA Model is a Representation of reality that is simple enough to gain A Model is a Representation of reality that is simple enough to gain understanding of the many interacting componentsunderstanding of the many interacting components
Dynamic behavior can be studied experimentally Dynamic behavior can be studied experimentally Physical and chemical processes are incorporated into a Physical and chemical processes are incorporated into a
system system model. model. Interactions and long-term responses to a system disturbance Interactions and long-term responses to a system disturbance
require modelingrequire modeling
Ecosystems are made up of many interacting components and therefore, Ecosystems are made up of many interacting components and therefore, can be modeled to simulate interactions and mechanisms at global and can be modeled to simulate interactions and mechanisms at global and regional levels. regional levels.
Once parameters are determined from existing processes, input Once parameters are determined from existing processes, input values can be manipulated to make predictions values can be manipulated to make predictions
on future on future outcomes in the system.outcomes in the system.
Computer modeling programs attempt to mathematically simulate Computer modeling programs attempt to mathematically simulate climates using predetermined parameters.climates using predetermined parameters.
What Stella Models Looks LikeWhat Stella Models Looks Like
Solar Flux
Atmosphere
Sun2Atm
Earth2Atm
Atm2Earth
Thermal
Atm2Space
albedo
fb
te
Ra
Aspects of Climate Modeling:Aspects of Climate Modeling:Many interactions and processes need to be incorporated into models to Many interactions and processes need to be incorporated into models to
insure accuracy.insure accuracy.
key systems for:
1. Atmosphere
2. Oceans
3. Biosphere
4. Cryosphere
5. Geosphere
Climate Forcing FactorsClimate Forcing Factors Internal FactorsInternal FactorsAtmospheric compositionAtmospheric composition
Amount of clouds (reflected Amount of clouds (reflected radiation radiation and absorption of and absorption of radiation)radiation)ChemistryChemistry
Surface CharacteristicsSurface CharacteristicsAmount and location of ice Amount and location of ice Amount of incoming solar Amount of incoming solar radiationradiationTemperature riseTemperature risePrecipitationPrecipitationSoil MoistureSoil Moisture
Oceanic CurrentsOceanic CurrentsChemistryChemistryShape, location and scale of Shape, location and scale of ocean ocean circulation circulation
Continental DriftContinental Drift
External FactorsAstronomical
Solar Output Orbital Changes Interplanetary dust Collisions with other
interplanetary bodies comets asteroids
Feedback MechanismsFeedback Mechanisms
The incorporation of key components of The incorporation of key components of the earth system requires an the earth system requires an
analysis of fundamental feedback analysis of fundamental feedback mechanisms.mechanisms.
A self-perpetuating mechanism of change, directed by inputs in and out of the system which result in a transient response to that change.
Modeling ActivityModeling Activity
YEAH!!! We’re Having
FUN!!!!!
Climate Feedback MechanismsClimate Feedback Mechanisms
Coupled reactions influencing climate sensitivity, patterns of change and transient response of climate.
ExamplesTemp & Albedo: Temp increases → Ice cover decreases → Albedo decreases → Temp(++) positive feedback
Temp &Water Vapor: Temp increases→ Water Vapor increases → Greenhouse gas increase→ Temp(++) → Water Vapor increase→ Clouds increase→ Albedo increase→ Temp decreases negative feedback
Positive FeedbackPositive FeedbackThe response of a system to a variable is to continue on a destabilizing path. If left unchecked the system becomes
unbalanced and homeostasis is lost.
Negative FeedbackNegative FeedbackNegative feedback helps to maintain stability in a system in spite of Negative feedback helps to maintain stability in a system in spite of
external changes. external changes. The system responds to the variable by reversing system responds to the variable by reversing the effects of the change.the effects of the change.
Self regulating system that maintains a state of equilibrium despite Self regulating system that maintains a state of equilibrium despite perturbations. perturbations.
Ice-Albedo Mechanism
Temperature goes up, ice caps melt revealing dark rock, albedo of surface goes down, temperature goes up
(Positive Feedback System)
Ice-Albedo Mechanism
Temperature goes up, ice caps melt revealing dark rock, albedo of surface goes down, temperature goes up
(Positive Feedback System)
Cloud-Albedo mechanism
As temperature rises, evaporation increases, leading to increased cloud formation, increasing albedo, thereby lowering temperature
(Negative Feedback System)
Earth Albedo is a function of surface type
Atmospheric CoolingAtmospheric Cooling
High-latitude VegetationHigh-latitude Vegetation FeedbackFeedback
Cooling
Vegetation Shifts
Surface Albedo Increase
More Cooling
Atmospheric
Ecological Model Types Discussed Ecological Model Types Discussed in Readingin Reading
Illustrate high levels of sensitivity in high-Illustrate high levels of sensitivity in high-latitude vegetation.latitude vegetation.
Equilibrium Biogeographical ModelsEquilibrium Biogeographical Models
Frame-based transient ecosystems modelsFrame-based transient ecosystems models
Dynamic Global Vegetation Models (DGVMs)Dynamic Global Vegetation Models (DGVMs)
Equilibrium Biogeographical ModelsEquilibrium Biogeographical Models
Application to high latitude system
In Simulation, the equilibrium response of vegetation to increased surface warming is that tundra vegetation will decrease in areas of greenhouse gas induced climate change scenarios and be
replaced by the upward shift of boreal woodlands. Despite this extension, boreal and woodland forests decrease in total land area due to a greater pole-ward expansion of temperate forests.
Used to model vegetation and climate interactions• Determine regional distribution of vegetation types
within a given climate scenarioUse a combination of mechanisms to develop model In general, disturbance regimes are not consideredExamples: BIOME3, MAPSS and DOLLY
Limitations of ModelLimitations of Model
Lacks consideration of various mechanism Lacks consideration of various mechanism interactions and responses interactions and responses
Model does not include such variables as nutrient availability and the response of photosynthesis to elevated CO2.Permafrost and its role in controlling vegetation disruptionPermafrost and its role in controlling vegetation disruptionIn some models, the total effects of disturbance (ex Fire) In some models, the total effects of disturbance (ex Fire) on vegetation compositionon vegetation composition
Does not simulate the rate of transitions of vegetal Does not simulate the rate of transitions of vegetal and climate states in response to climate and climate states in response to climate associated variables. associated variables.
Frame-Based Transient Frame-Based Transient Ecosystem ModelsEcosystem Models
Model consists of a series of sub-models within their own barriers, each simulating transient changes of different ecosystem types
Spatial interactions among neighboring regions can be simulated. This is described as a GRID BASED SIMULATION.
Each ecosystem type is modeled separately so that differences among ecosystems are incorporated within each sub-model
Sub-models originally absent from model can be conceived and added into model simulations.
Individual models can be expanded to simulate other model variability
Allows modelers to track succession and disturbance (fire and insect attack)
Can determine probability of switching to one ecosystem type over another. When switching occurs another sub-model
is activated which then stimulates other factors to activate.
Frame-Based Transient Frame-Based Transient Ecosystem Models cont.Ecosystem Models cont.
Application to high latitude systemIn simulation, the boreal forests move upwards towards the poles. A
gradual change in tree invasion, climatic probability of fire, and disease are established as a function of climate.
The rate of vegetation change is dictated by the rate of climate change.
Climatic changes cause biome composition to destabilize. Equilibrium is not achieved.
Limitations of ModelLimitations of Model
Smaller mechanisms and interactions become overlooked Smaller mechanisms and interactions become overlooked by the larger picture.by the larger picture.
Ecosystems are strictly defined within there prescribed sub-Ecosystems are strictly defined within there prescribed sub-model. Combinations of interactions among vegetation model. Combinations of interactions among vegetation and other factors are simulated in a manner where and other factors are simulated in a manner where movement of existing plant communities is not movement of existing plant communities is not considered. The model’s results are focused on new considered. The model’s results are focused on new associations with vegetation and environment, associations with vegetation and environment,
Dynamic Vegetation ModelsDynamic Vegetation ModelsThe integration of biogeogeography and biogeochemistry models into transient models illustrates ecological effects of climate change, in real time. DGVMs effectively model disturbances and incorporate natural constraints on biomass. They are useful for modeling vegetation climate change reactions and can incorporate disturbances such as fire or insect infestation.
The Basics:
1. Integrate vegetation structure and function.
2. Simulate the responses of integrated structure and function to changing climate conditions.
Plant Functional TypesPlant Functional Types
Examples of Plant Functional Examples of Plant Functional Types:Types:
Broadleaf treesBroadleaf trees Needle leaf treesNeedle leaf trees ShrubsShrubs C3 GrassC3 Grass C4 GrassC4 Grass
It is not possible to model plant species on an individual level. The concept of PFTs allows for the grouping of species, reducing the variables of the model to a manageable level.
Plants are classified in a functional way, however there is no single or universal format for PFTs. PFTs are thus specific to the issues being addressed in the model.
Assumptions of PFTs:
1. Species can be grouped according to structural and functional characteristics.
2. Parameterizations of each functional type represent the species within the group, with little variance.
3. Biogeography does not matter.
Biogeochemistrybiogeography
Fire Module
Preliminary Results for NASA DGVM Preliminary Results for NASA DGVM StudiesStudies
Model limitations:
•Does not consider disturbances such as fire.
•No consideration of Plant seed limitations or dispersal mechanisms.
The NASA-CASA DGVM correctly predicts forested area in 75%-95% of cases worldwide and 58% of all grassland scenarios.
Improvements of DGVMs for Improvements of DGVMs for Northern EcosystemsNorthern Ecosystems
Inclusion of anaerobic soil processesInclusion of anaerobic soil processes
Permafrost dynamicsPermafrost dynamics
Moss-lichen layer dynamicsMoss-lichen layer dynamics
Broader disturbance regimes Broader disturbance regimes (insect outbreaks (insect outbreaks and land management changes)and land management changes)
Plant Functional Types schemes specific to Plant Functional Types schemes specific to high-latitude environments.high-latitude environments.
Overall Northern Latitude Climate Overall Northern Latitude Climate Change ProjectionsChange Projections
Modeled ProjectionsModeled ProjectionsUpward polar-shift of boreal woodlands and temperate forestsUpward polar-shift of boreal woodlands and temperate forests
Shifting Plant Communities. An increase in temperature, chemical Shifting Plant Communities. An increase in temperature, chemical abundance and albedo may alter the competitive abilities between two abundance and albedo may alter the competitive abilities between two or more species, thereby affecting the composition of a natural or more species, thereby affecting the composition of a natural community. Photosynthesis and period of growth may be enhanced.community. Photosynthesis and period of growth may be enhanced.
Reaction of vegetation to increased saturation and nutrient Reaction of vegetation to increased saturation and nutrient content.content.
Rising CO2 will increase temperature and in turn increase evaporation Rising CO2 will increase temperature and in turn increase evaporation from tundra. from tundra.
Arctic tundra may change from net sink to a source of CO2 (Billings et Arctic tundra may change from net sink to a source of CO2 (Billings et al. 1983). al. 1983).
Increase of organic decomposition rate, which will in turn change soil Increase of organic decomposition rate, which will in turn change soil composition.composition.
Are climate models reliable?Are climate models reliable?
Models are tested by comparing model Models are tested by comparing model predictions to current and past climates.predictions to current and past climates.
A lack of knowledge of biological processes A lack of knowledge of biological processes makes models difficult to verify.makes models difficult to verify.
There are flaws in climate models, this must There are flaws in climate models, this must be considered when using models.be considered when using models.
