Population and Climate Change: Coupling Population Models ...ekalnay/pubs/... · Population growth 20117.0b 19986.0b 19875.0b 19754.0b 19603.0b 19272.0b 18001.0b 16500.5b 1AD0.3b

Population and Climate Change:Population and Climate Change:Coupling Population Models withCoupling Population Models with

Earth System ModelsEarth System Models

Safa Motesharrei, Jorge Rivas, Fang Zhao,Eugenia Kalnay, Victor Yakovenko, Matthias Ruth

Ning Zeng, Fernando Miralles-Wilhelm,Cortney Gustafson, Bob Cahalan

WCRP 28 October 2011

Without fullycoupling we

could not predictENSO!

We are still missingthe most importantcomponent of theEarth System: theHuman System

Population growth

7.0b20116.0b19985.0b19874.0b19753.0b19602.0b19271.0b18000.5b16500.3b1AD

Population and climate: a study at theLondon School of Economics

Per dollar spent,family planning reduces four

times as much carbon overthe next 40 years as

adopting low-carbontechnologies

Concluded: Family planning iscost effective and should bea primary method to reduceemissions

Copenhagen: no discussion onpopulation or familyplanning: it is a taboosubject

New UN projection is higher

2010 UN medium projection

2006 UN medium projection

Why was the population able to grow so fastsince the 1950’s?

Two reasons:1) Sanitation and antibiotics (living longer)2) Use of fossil fuels in agriculture starting in the 1950’s:

- fertilizers, pesticides, irrigation, mechanization (GreenRevolution).

1950 to 1984: production of grains increased by 250% and thepopulation doubled

Without fossil fuels population would be much smaller!• Growth in grain production is now flattening out• Industrial farming is destroying forests, soil• Urban and suburban sprawl is overrunning best farmlandThis is not sustainable: “We are drawing down the stock of

natural capital as if it was infinite” (Herman Daly)

Example: North Korea, got cheap oil from theformer Soviet Union until early 1990s

Production of grain inNorth Korea, updated to 2008

Source: FAO, www.wolfatthedoor.org.uk

The famines in North Korea are theresult of the sudden loss of access

to abundant fossil fuel

The Club of Rome commissioned a group at the MIT SloanSchool of Management to study:

“Are current policies leading to a sustainable future or tocollapse?”

When the results appeared in 1972, the conclusion thatwith finite natural resourcesgrowth would overshoot and collapsewas dismissed as absurd by manyeconomists. (“discredited”)

35 years later the “standard run” modelcompares well with reality for allvariables.(Graham Turner, 2008, Ugo Bardi, 2011)

1972: Club of Rome “Limits to Growth”

The model could havefour possible types of outcomes

Infinite World Ideal(no overshoot)

DisasterHopefully…

You are here… Or here…

The results are sobering:most scenarios collapse

Even if resources are doubled,collapse is only postponed ~20 years

In order to avoid collapse, governmentpolicies are needed to:

• Stabilize population and• Stabilize industrial production per person• Adopt technologies to

– abate pollution– conserve resources– increase land yield– protect agricultural land

Standard Neoclassical Economic Model

The standard Neoclassical Economic Model does not account for:• Inputs (resources)• Outputs (pollution)• Stocks of Natural Capital• Dissipation of Energy (i.e., a Perpetual Motion Machine)• Depletion, Destruction or Transformation of MatterTherefore, no effects on the Earth System, and No Limits to Growth.

Firms: Households:

Labor and Capital

Goods and Services

As Herman Daly, Robert Costanza, and other scholars in the field of Ecological Economics describe,

Realistic Ecological Economic Model (Herman Daly)• Incorporates INPUTS, including DEPLETION of SOURCES• Incorporates OUTPUTS, including POLLUTION of SINKS

Sinks:Oceans,

AtmosphereLand

Population óTechnology Population growth rate Energy Use / Capita Resource Use / Capita Emissions produced / Capita Waste produced / Capita Economic expansion / Capita

Outputs:1. Emissions CO2, Methane, etc2. Waste ProductsGarbage, Toxics, etc 3. Surface ChangesUrbanization, Deforestation, Desertification, etc

Inputs:1. EnergyOil, Coal, Gas, Nuclear, Biomass, Renewables, etc

2. MatterSoil, Minerals,Lumber, and Other MaterialsResources

Sources:Stock of Natural Capital

Flows of Energy

Feedbacks in an Ecological Economic ModelOf course, the OUTPUTS and the filling up of SINKS, have feedbacks on the

Human Economy, the Quantity and Quality of the INPUTS, and the depletionof SOURCES :

Sinks:Oceans,

AtmosphereLand

Population óTechnology Population growth rate Energy Use / Capita Resource Use / Capita Emissions / Capita Waste / Capita Economic expansion / Capita

Outputs:1. Emissions CO2, Methane, etc2. Waste ProductsGarbage, Toxics, etc 3. Surface ChangesUrbanization, Deforestation, Desertification, etc

Inputs:1. EnergyOil, Coal, Gas, Nuclear, Biomass, Renewables, etc

2. MatterSoil, Minerals,Lumber, and Other MaterialResources

Sources:Stock of Natural Capital

Flows of Energy

“Empty World” Model• Throughout most of human history, the Human Economy was so small relative to

the Earth System, that it had little impact on the Sources and Sinks.• In this scenario, the standard isolated economic model might have made sense.

Sinks:

Inputs:

Sources:

Outputs:

But Population and Economic Output per Capitahave grown, and the net impact is their product!

Technology allows more efficient production, but also much faster consumption!

Sources:

Inputs:

“Full World” Ecological Economic Model• Today, the Human Economy has grown so large, it has very large Effects

on the Earth System, Depleting the Sources and Filling the Sinks. It isclear that growth cannot continue forever.

Sinks:

Outputs:

Regional Population Modelswith two-way coupling is needed!

Local Sinks:Oceans,

AtmosphereLand

Pop óTechn REGION 1

Outputs:Inputs

Local Sources:

Local Sinks:Oceans,

AtmosphereLand

Pop óTechn REGION N

Outputs:Inputs

Local Sources:

…

GlobalSources:

Global Sinks:Oceans,

AtmosphereLand

Some of the Essential Feedbacks needed• Vegetation <=> albedo (climate change)• CO2 emissions <=> climate change <=> vegetation• Vegetation <=> water use, fossil fuel use <=> crops• Population <=> crops, food/capita <=> mortality• Population <=> food/capita <=> fisheries• Population <=> CO2 emission, pollution <=> atmosphere, land• Population <=> urban sprawl <=> loss of cultivated land• Technology <=> non-renewable resources <=> alternative resources• Policies <=> education, birth rate <=> pollution, emissions• Resource depletion <=> trade, resource conflicts• Population <=> CO2 emissions <=> climate change <=> vulnerability

We proposed to experiment first using an intermediateEarth System model (Speedy-VEGAS) and a prototypeHuman-Economy-Population model.

Government policies are important!

The red (highest NDVI vegetation index) is in the province ofMisiones, Argentina, that protects the forest.

Compare Misiones with Brazil, Paraguay and the rest of Argentina!

Coupled Simple Water Submodel (SIWA)

Earth SystemUMD/ICTP

Human System(region n)

Oceans

WasteWater

WaterSources

Population

Demographics

Water/capita

Enough?

If not,Increase use/

Increasetechnology

PrecipitationConsumed

Water

Net WaterDemand

FreshWaterSupply

PipelineD

istribut

Collection

Efficiency

Leaks

WasteWater

Recycling

Freshwater

Treatment

Waste WaterTreatment

Avail.Water

Runoff

Techn

Evaporation

Land Model

River inflowRiver outflow

Atmosphere

Other regions

trade

migration

Human and Nature Dynamical model (HANDY)with Rich and Poor: for thought experiments

!y = Regeneration! y(1" y) " Production# xPy

x = xR + xPNature equation: (only the poor produce!)

Total population: Rich +Poor

The rich elite accumulates wealth from the work of everyone else (herereferred to as the poor). When there is a crisis (e.g., famine) the elite canspend the accumulated wealth to buy food.

Population equations: death rate depends on whether there is enough food:

The Wealth belongs to the Rich: Inequality factor

!W = Production - Poor consumption - Rich consumption =!x py " sxp "# sxR

! ~ 100

!xP = !"PxP + #PxP!xR = !"RxR + #RxR

Just 4 equations!

Human and Nature Dynamical model (HANDY)with Rich and Poor: a thought experiment

Nature

Rich Population

Poor Population

Wealth

Rich Poor

NatureWealth


• Nature declines with population growth• Using their wealth, the Rich canshield themselves from environmentaldegradation, which first affects thepoor• Eventually it reaches the upperclasses as well, when it is too late totake preventive measures

By the end of the 20th century, having surpassed the sustainablecarrying capacity of the planet, the population is drawing down the

accumulated capital to survive

Nature

Rich

Poor

Wealth


Nature

Rich

Poor

Wealth

• Nature declines with population growth• Using their wealth, the Rich canshield themselves from environmentaldegradation, which first affects thepoor• Eventually it reaches the upperclasses as well, when it is too late totake preventive measures

This thought experiment shows how a crisis can happenrapidly, even though it appears that population is rising

steadily without any problems, and that the wealthy wouldnot feel the effects of the collapse until it is too late for the

poor (and then it is too late for the rich as well!).

Population, Nature, and Wealth100,000 ppl

100 eco$2,000 eco$

50,000 ppl50 eco$

1,000 eco$

0 ppl0 eco$0 eco$

1750 1850 1950 2050 2150 2250Time (Year)

"kappa * x R equivalent rich population" : Current pplx P Poor Population : Current pplchi population carrying capacity : Current pplchi M optimal population carrying capacity : Current pply Nature : Current eco$w Accumulated Wealth : Current eco$

Nature

Poor Population

Rich Population(equivalent)

Wealth

Catton: Overshoot (1980)

• “Carrying capacity”: maximum population that can besustainably supported by the habitat (nature).

• “Overshoot”: Growth beyond an area’s carryingcapacity, leading to Collapse.


100 eco$2,000 eco$

50,000 ppl50 eco$

1,000 eco$

0 ppl0 eco$0 eco$

1750 1850 1950 2050 2150 2250Time (Year)


Nature

Poor Population


Wealth

Optimal Carrying Capacity

Carrying Capacity

This is the typical overshoot the carryingcapacity followed by a collapse

If we reduce the production to its optimal valuewe can reach a steady state and survive


100 eco$400 eco$

300,000 ppl50 eco$

200 eco$

0 ppl0 eco$0 eco$

1750 1900 2050 2200 2350 2500 2650Time (Year)


Nature

Population

Wealth


No Rich or Poor: egalitarian society lives at an optimal level


100 eco$400 eco$

300,000 ppl50 eco$

200 eco$

0 ppl0 eco$0 eco$

1750 1900 2050 2200 2350 2500 2650Time (Year)


Nature


Wealth


Now we add an initial 0.1% of Rich…

Poor Population

Initially the society still goes towards equilibrium, while the Rich are very few

?

After the Rich grow, they consume thewealth and the society collapses


100 eco$400 eco$

300,000 ppl50 eco$

200 eco$

0 ppl0 eco$0 eco$

1750 1900 2050 2200 2350 2500 2650Time (Year)


Nature

Rich Population(equivalent)Poor Population


Wealth

• Atoms in a gas are identical, but the probability distribution P(E)of their energies E is highly unequal, with few atoms havinghigh energies and many atoms having low energies.

• In statistical physics, P(E) is given by the exponentialBoltzmann-Gibbs distribution following from maximization ofentropy in the ensemble of interacting atoms.

• Yakovenko applied a similar probabilistic approach toensembles of interacting economic agents (i.e., people), withremarkable agreement with IRS data

Analogy between atomic distribution ofAnalogy between atomic distribution ofenergy and energy and the the distribution of incomedistribution of income

((Yakovenko Yakovenko et al., 2000, et al., 2000, ……))

Yakovenko (2000) applied a similar probabilistic approach toensembles of interacting economic agents and obtained probability

distributions that are in remarkable agreement with the empirical data

“the top 3%”

“the bottom 97%”

An analysis between 1983 and 2008 of IRS dataAn analysis between 1983 and 2008 of IRS datashows that shows that the inequality increasedthe inequality increased and and

all the growth went to the top 3%all the growth went to the top 3%

Gini coefficient of inequality(increases)

Exponent of the Pareto distribution

Percentage of total income in the “rich tail”

Our plansOur plans• Continue developing the submodels of the

Prototype Human system and fully couplingwith the Earth System.

• Post the codes…• Couple the Yakovenko statistical model with

the HANDY model first, replacing theRich/Poor classes with realistic continuumwealth distributions.

• Apply the same statistical analysis to the fullprototype coupled system.

• We welcome multidisciplinary collaborations!

Population and Climate Change: Coupling Population Models ...ekalnay/pubs/... · Population growth 20117.0b 19986.0b 19875.0b 19754.0b 19603.0b 19272.0b 18001.0b 16500.5b 1AD0.3b

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