Tom AckermanTom Ackerman

Professor, Department of Atmospheric SciencesProfessor, Department of Atmospheric Sciences

Planet Earth has warmed over the Planet Earth has warmed over the last 100 yearslast 100 years

Data analyzed by Hadley Research Centre, United Kingdom

Probable CauseProbable CauseIncrease in greenhouse gas Increase in greenhouse gas

concentrationsconcentrations

Antarctic Ice Core Data

250

270

290

310

330

350

370

390

1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000

Year

CO

2 C

on

cen

trat

ion

, pp

m

Mauna Loa Data

Pre-industrial level

Atmosphere Carbon balanceAtmosphere Carbon balance

Fossil fuel emission6.1 GTon / year

Deforestation1.5 GTon /year

Total~7.5 GT / year

Increasing CO2 in atmosphere 3 GT / year

Uptake in mixed layer 2.5 GT / year

Reforestation in NA 0.5 GT / year

Total~ 6 GT / year

The FactsThe Facts

Surface temperature is increasingSurface temperature is increasing Increase is unprecedented in last 1000 Increase is unprecedented in last 1000

years (and probably more)years (and probably more)CO2 is on the rise – up about 35%CO2 is on the rise – up about 35%About 20% of the CO2 emission cannot be About 20% of the CO2 emission cannot be

accounted for at present!accounted for at present! Increasing CO2 causes increasing surface Increasing CO2 causes increasing surface

temperaturetemperature

Okay, so the question is:Okay, so the question is:

What’s going to happen to global What’s going to happen to global climate over the next 10 to 50 years?climate over the next 10 to 50 years?

Corollary:Corollary:

How would we know?How would we know?

Let’s build a CLIMATE model!Let’s build a CLIMATE model!

Atmosphere

H2O vapor and CloudsAbsorbing gases – CO2

Aerosol

What do we need in our climate model?What do we need in our climate model?

Ocean

IceSea ice

Ice sheets (glaciers)

Biota

Surface vegetation

Complete 4D model

Coordinates:

Latitude

Longitude

Height

Time

Constructing a climate modelConstructing a climate model

Decide on the variables – what do we want to Decide on the variables – what do we want to predict?predict?

T, wind speed (3D), water vapor concentrationT, wind speed (3D), water vapor concentration Write down time-dependent equations Write down time-dependent equations

Temp (time = t + Temp (time = t + t) = Temp (time = t) t) = Temp (time = t)

+ (all the things that change the temperature) + (all the things that change the temperature)

Can’t solve these equations exactly Can’t solve these equations exactly

Typical values for current ATMOSPHERE ONLY

climate models

5 variables (minimum)

8190 boxes

26 vertical levels

30 minute time step (48/day)

51.1 million equations / day

18.6 billion equations / year

How big is big?How big is big?300 km x 300 km

Climate modeling challenges the biggest Climate modeling challenges the biggest computerscomputers

Japanese Earth Simulator

CRAY

IBM Blue Sky (NCAR)

Let’s RUN our climate model!Let’s RUN our climate model!

How to run a climate modelHow to run a climate model

Coupled Global Climate ModelAtmosphere

Initial condition

s

Ocean

Run forward in time for at least 10 to 30 years

Compare averaged model results with averaged

climate results

Prescribed forcing (Sun, CO2, etc.)

Major questionsMajor questions

Can we simulate climate change over the Can we simulate climate change over the past 100 years?past 100 years?

Is it possible that the current increase in Is it possible that the current increase in temperature is a result of natural variability temperature is a result of natural variability in the climate system?in the climate system?

Simulating the last 150 yearsSimulating the last 150 years

Input natural forcing into climate modelInput natural forcing into climate modelVolcanic aerosolVolcanic aerosolSolar activitySolar activity

Input anthropogenic forcingInput anthropogenic forcingCO2 and other greenhouse gasesCO2 and other greenhouse gasesSulfate aerosolSulfate aerosol

Input bothInput both

IPCC ConclusionIPCC Conclusion

In the light of new evidence and taking into In the light of new evidence and taking into account the remaining uncertainties, most account the remaining uncertainties, most of the observed warming over the last 50 of the observed warming over the last 50 years is likely to be due to the increases in years is likely to be due to the increases in greenhouse gas concentrations.greenhouse gas concentrations.

Predicting the futurePredicting the future

Intergovernmental Panel on Climate Change Intergovernmental Panel on Climate Change (IPCC) – est. 1988(IPCC) – est. 1988

IPCC is an assessment activity – it does not sponsor research or monitor climate

Information chain leading to a climate projection

Projecting the future: ScenariosProjecting the future: Scenarios

Estimate future emissions of greenhouse Estimate future emissions of greenhouse gases and pollutantsgases and pollutantsCO2CO2Other greenhouse gasesOther greenhouse gasesAerosol (sulfate, carbon)Aerosol (sulfate, carbon)

YearYear [CO2] [CO2] ppmvppmv

19731973 330330

19831983 343343

19931993 357357

20042004 377377

Rate of increase in CO2 due to emissions:

73 – 03 1.5 ppmv / year

93 – 03 1.8 ppmv / year

Assumption: we can tolerate a climate change corresponding to 600 ppmv

Question:

1. How many years will it take to reach 600 ppmv at an emission rate of 1.5 ppmv / year?

Currently (2004) at 377 ppmvCurrently (2004) at 377 ppmvAmount of extra CO2: Amount of extra CO2:

600 – 377 = 223 ppmv600 – 377 = 223 ppmvLength of time to accumulate Length of time to accumulate

= amount / rate= amount / rate

= 223 ppmv / (1.5 ppmv / year)= 223 ppmv / (1.5 ppmv / year)

= 149 years= 149 years

YearYear [CO2] [CO2] ppmvppmv

19731973 330330

19831983 343343

19931993 357357

20042004 377377

Rate of increase in CO2 due to emissions:

73 – 03 1.5 ppmv / year

93 – 03 1.8 ppmv / year

Assumption: we can tolerate a climate change corresponding to 600 ppmv

Questions:

1. How many years will it take to reach 600 ppmv at an emission rate of 1.5 ppmv / year? = 149 years

2. At an emission rate of 1.8 ppmv / year? = 124 years

3. So what are we worried about?

A1: A world of rapid economic growth and rapid introductions of new and more efficienttechnologies

A2: A very heterogenous world with an emphasis on familiy values and local traditions

B1: A world of „dematerialization“ and introduction of clean technologies

B2: A world with an emphasis on local solutions to economic and environmental sustainability

IS92a „business as usual“ scenario (1992)

IPCC ScenariosIPCC Scenarios

Emissions scale with population

Population increases exponentially (not linearly)

Emissions increase exponentially (not linearly)

Summary: ScenariosSummary: Scenarios

CO2 concentrations in this century vary CO2 concentrations in this century vary widely depending on assumptions about widely depending on assumptions about technology use and energy mixtechnology use and energy mix

By 2100, we could have CO2 By 2100, we could have CO2 concentrations exceeding 900 ppmv; hard concentrations exceeding 900 ppmv; hard to see how we would have less than ~ 500 to see how we would have less than ~ 500 ppmvppmv

So now let’s put those CO2 So now let’s put those CO2 estimates into our climate modelestimates into our climate model

(“force” our model with CO2)(“force” our model with CO2)

Start of Lecture 2Start of Lecture 2

Where we are …Where we are …

““Built” a climate modelBuilt” a climate modelUsed the climate model to simulate last Used the climate model to simulate last

150 years – did a pretty good job150 years – did a pretty good jobDeveloped scenarios for the future – Developed scenarios for the future –

based on projected energy usebased on projected energy useStarted to look at climate change over this Started to look at climate change over this

during this centuryduring this century

A1: A world of rapid economic growth and rapid introductions of new and more efficienttechnologies

A2: A very heterogenous world with an emphasis on familiy values and local traditions

B1: A world of „dematerialization“ and introduction of clean technologies

B2: A world with an emphasis on local solutions to economic and environmental sustainability

IS92a „business as usual“ scenario (1992)

IPCC ScenariosIPCC Scenarios

Figure SPM-5Figure SPM-5Updated: 13 Feb 2007

Figure SPM-6Figure SPM-6

Sea level riseSea level rise

““Commitment”Commitment”

Even if we stopped emitting CO2 today, Even if we stopped emitting CO2 today, we are we are committedcommitted to more warming and to more warming and more sea level rise because we have to more sea level rise because we have to wait for the climate system to come into wait for the climate system to come into equilibrium with the current atmospheric equilibrium with the current atmospheric concentration of CO2concentration of CO2

Summary of effects (very certain)Summary of effects (very certain)

The globally averaged The globally averaged surface temperaturesurface temperature is projected is projected to increase by 1.4 to 5.8°C by 2100. to increase by 1.4 to 5.8°C by 2100. The projected The projected rate of warmingrate of warming is much larger than the observed is much larger than the observed

changes during the 20th century and is very likely to be without changes during the 20th century and is very likely to be without precedent during at least the last 10,000 years.precedent during at least the last 10,000 years.

Global mean Global mean sea levelsea level is projected to rise by 0.1 to 0.9 is projected to rise by 0.1 to 0.9 meters between 1990 and 2100. meters between 1990 and 2100. Global mean Global mean surface temperaturesurface temperature increases and rising increases and rising sea sea

levellevel from thermal expansion of the ocean are projected to from thermal expansion of the ocean are projected to continue for hundreds of years after stabilisation of greenhouse continue for hundreds of years after stabilisation of greenhouse gas concentrations (even at present levels)gas concentrations (even at present levels)

Could be more if ice sheets experience catastrophic failureCould be more if ice sheets experience catastrophic failure

Figure SPM-7Figure SPM-7

Summary of effects (probable)Summary of effects (probable)

We expectWe expect Greater year-to-year variability in precipitationGreater year-to-year variability in precipitation More intense precipitation eventsMore intense precipitation events Higher frequency of hot to very-hot daysHigher frequency of hot to very-hot days Increased risk of summer drought over continental Increased risk of summer drought over continental

interiorsinteriors Decrease in NH snow cover and sea ice extentDecrease in NH snow cover and sea ice extent Continued shrinking of glaciers and ice capsContinued shrinking of glaciers and ice caps Antarctic ice sheet will increase in mass (increased Antarctic ice sheet will increase in mass (increased

precipitation), while Greenland ice sheet will decreaseprecipitation), while Greenland ice sheet will decrease

So what does this mean for us?So what does this mean for us?

Changes in regional Changes in regional hydrology – more rain hydrology – more rain with less snow packwith less snow pack

Reduced stream flow in Reduced stream flow in summer – impacts on summer – impacts on fisheries and irrigationfisheries and irrigation

Increased storm surge Increased storm surge and coastal erosionand coastal erosion

From an article in the February 20, 2004 issue of Science

So what do we do about this?So what do we do about this?

1992 United Nations Framework 1992 United Nations Framework Convention on Climate ChangeConvention on Climate Change

GOAL: “…stabilization of greenhouse GOAL: “…stabilization of greenhouse gas concentrations in the atmosphere gas concentrations in the atmosphere at a level that would prevent dangerous at a level that would prevent dangerous anthropogenic interference with the anthropogenic interference with the climate system.” (Article 2)climate system.” (Article 2)

P.S. Our country is a signatory!

Four types of policy responsesFour types of policy responses

1.1. Emissions mitigation (reduce Emissions mitigation (reduce CO2 output)CO2 output)

2.2. Adaptation (design to meet Adaptation (design to meet expected changes)expected changes)

3.3. Improvement in scientific Improvement in scientific understandingunderstanding

4.4. Technology development Technology development

If we are going to stabilize climate,If we are going to stabilize climate,

we have to stabilize atmosphere COwe have to stabilize atmosphere CO22,,

which means,which means,

we have to drive anthropogenic COwe have to drive anthropogenic CO22

emissions to 0!emissions to 0!

THIS IS SCARY!

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

1990 2010 2030 2050 2070 2090

PgC

/yr

IS92a(1990 technology)

IS92a

550 Ceiling

Implicit assumption of major technological Implicit assumption of major technological

change over the next centurychange over the next century

Stabilization requires additional policies and technology developments that can compete economically because carbon has a ‘value’

This improvement presumes fully developed:

SolarNuclearEfficient Fossil ElectricAdvanced TransportationEnd Use Efficiency

What are some of the key “new” What are some of the key “new” technologies?technologies?

Carbon capture and disposalCarbon capture and disposal The removal of carbon from a fossil fuel process stream and the The removal of carbon from a fossil fuel process stream and the

disposal of it in a place well-isolated from the atmosphere.disposal of it in a place well-isolated from the atmosphere. Renewable resources (physical and chemical)Renewable resources (physical and chemical)

Wind, solar, ocean tidesWind, solar, ocean tides HydrogenHydrogen

The use of hydrogen as an energy carrier, usually spoken of as The use of hydrogen as an energy carrier, usually spoken of as fuel cells with many applications, most notably transportationfuel cells with many applications, most notably transportation

‘‘Modern’ biomassModern’ biomass The emergence of energy crops as a source of hydrocarbons The emergence of energy crops as a source of hydrocarbons

derived from the fast part of the carbon cyclederived from the fast part of the carbon cycle

These technologies are not cheap and will not be These technologies are not cheap and will not be competitive with fossil fuels unless we subsidize themcompetitive with fossil fuels unless we subsidize them

The current energy supply (fossil fuel) is NOT free market. It is

• cartel owned • internationally dominated by a handful of large corporations• government regulated, subsidized and taxed

Current US PolicyCurrent US Policy

Rejected Kyoto accord -- 2001Rejected Kyoto accord -- 2001 Kyoto plan called for reductions in absolute GHG Kyoto plan called for reductions in absolute GHG

emissions for industrialized countries, but no reductions emissions for industrialized countries, but no reductions for developing countriesfor developing countries

Announced plan to reduce GHG emissions as a Announced plan to reduce GHG emissions as a function of GDP (Gross Domestic Product) – 2002 function of GDP (Gross Domestic Product) – 2002 at rate of 1.8% per yearat rate of 1.8% per year

Implemented Climate Change Science Program Implemented Climate Change Science Program (CCSP) -- 2002(CCSP) -- 2002

Basically business as usual!For the last 25 years (dating from the first oil crisis in the late 70’s),

this rate of reduction has been about 1.6%!

Basically business as usual!Simply replaced the US Global Change Research Program

What about improved What about improved understanding?understanding?

Research effort driven by federal budgetResearch effort driven by federal budget

Budget numbers in Millions of $US

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

Total US Budget Defense Dept. Climate research

1998

1999

2000

2001

2002

2003

2004

2005

Budget numbers in Millions of $US

0

200

400

600

800

1000

1200

1400

Defense Dept (By day) Climate research

1998

1999

2000

2001

2002

2003

2004

2005

Does not include supplementary appropriation for Iraq war

$2.70 / year for every person in the US

$1480 / year for every person in the US

US Policy ResponseUS Policy Response

Business as usualBusiness as usual

No plansNo plans

No new research focus; No new research focus; static funding for a static funding for a decade decade

Limited and poorly Limited and poorly focused (freedom car)focused (freedom car)

Emissions mitigationEmissions mitigation

AdaptationAdaptation

Improved understandingImproved understanding

Technology developmentTechnology development

Policy SummaryPolicy Summary

We (the US) are the largest part of the problem but We (the US) are the largest part of the problem but have have NO COHERENT STRATEGYNO COHERENT STRATEGY to address it to address it

(I could say that our current “policy” has moved from (I could say that our current “policy” has moved from benign neglectbenign neglect to to active opposition.active opposition.))

The Global Greenhouse ProblemThe Global Greenhouse Problem

We can mitigate the problem but we must We can mitigate the problem but we must begin to act begin to act NOW!NOW!

CO2 molecules have a long lifetime – the CO2 molecules have a long lifetime – the molecule you emit today will still be in the molecule you emit today will still be in the atmosphere in 100 yearsatmosphere in 100 years

The molecule you don’t emit is one less The molecule you don’t emit is one less “commitment” to global warming“commitment” to global warming

A technological A technological strategystrategy

Stabilization Wedges: Solving the Climate

Problemfor the Next 50 Years with

Current TechnologiesS. Pacala and R. Socolow

(Science, 2004)

Hybrid carsNuclear power

Not all wedges are equal – some have more effect early in the process, others take much longer; some are easier than others; some will fail!

Types of WedgesTypes of Wedges Conservation and efficiencyConservation and efficiency

Efficient cars (hybrid, H2)Efficient cars (hybrid, H2) Reduce dependence on carsReduce dependence on cars Improved building efficiencyImproved building efficiency Shift to more efficient fuelsShift to more efficient fuels Agriculture Agriculture

Types of WedgesTypes of Wedges Conservation and efficiencyConservation and efficiency

Efficient cars (hybrid, H2)Efficient cars (hybrid, H2) Reduce dependence on carsReduce dependence on cars Improved building efficiencyImproved building efficiency Shift to more efficient fuelsShift to more efficient fuels Agriculture Agriculture

RenewablesRenewables Solar Solar WindWind BiomassBiomass NuclearNuclear

CO2 sequestrationCO2 sequestration Increase standing biomass (reforestation)Increase standing biomass (reforestation)

In summaryIn summary

The Global Greenhouse ProblemThe Global Greenhouse Problem

Is Is REALREAL -- we will continue to add CO -- we will continue to add CO22 to the atmosphere to the atmosphere

and the climate will warm.and the climate will warm. Is Is LONG TERMLONG TERM -- a problem for decades, not years => -- a problem for decades, not years =>

YOUR PROBLEM!YOUR PROBLEM! Has Has IMPLICATIONS FOR SOCIETYIMPLICATIONS FOR SOCIETY -- global warming will -- global warming will

impact water resources, agriculture, energy usage, severe impact water resources, agriculture, energy usage, severe weather damage, sea level, etc., weather damage, sea level, etc., on a regional basis.on a regional basis.

We (the US) are the largest part of the problem but have We (the US) are the largest part of the problem but have NO NO COHERENT STRATEGYCOHERENT STRATEGY to address it to address it

The Global Greenhouse ProblemThe Global Greenhouse Problem

PRESENTS DIFFICULT ETHICAL AND MORAL PRESENTS DIFFICULT ETHICAL AND MORAL CHOICESCHOICES -- in any plausible forecast of the future, -- in any plausible forecast of the future, there there will bewill be losers; there losers; there maymay bebe some winners. some winners.

The biggest losers will most likely not be those who are The biggest losers will most likely not be those who are most responsible for the change in climate.most responsible for the change in climate. Who pays for their losses?Who pays for their losses? With what currency?With what currency? On what time scale?On what time scale?