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Chapter 20: Climate change and ozone depletion

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Predicting Climate Change

• Volcanic eruption 1991 Philippines

• Cool earth 0.5ºC over 15months, return to normal by 1995

• Model accurately predicts• Significance?

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Glacial and interglacial periods

Caused by...?• Change in elliptical orbit of earth• wobble of axis• sun spots, solar magnetic cycles• volcanic eruptions

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• Current interglacial period

• Rise in last century?

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Temperatures in past?• Historic temperatures determined by proxy

measures> tree ring widths, coral growths, isotope in ice,

borehole temperatures• Analyze ice cores: levels of CO2 in troposphere

correlate with temperature

http://earthobservatory.nasa.gov/Features/Paleoclimatology_OxygenBalance/

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3 factors that shape earth's climate:• Solar energy• Greenhouse effect• Ocean• *natural cooling

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Greenhouse Gases:• CO2

• CH4

• H2O• N2O

Burning fossil fuels

Clearing/burning forests (Deforestation)

Planting rice/using inorganic fertilizers (agriculture)

Which countries emit most greenhouse gasses?• US• China• EU

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IPCC: Intergovernmental Panel on CLimate Change

Evidence for global warming:• Warmer average temperatures• 10 warmest years since 1861 happened since 1990• Arctic temperatures rising twice as fast as rest of

world• glaciers/sea ice melting• permafrost melting--release CO2 and CH4

• Rising sea levels> melting ice> expanding sea water

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Computer Models Predict Effects of Various Factors

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Predicted change:• Very likely that earth's mean surface temperature

will increase by 2.4-5.4ºC between 2000 and 2100• Higher than average temperature at

> earth's poles> land > oceans> interior of continents

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Consequence of Climate Change

• Happening very fast= no time to adapt> ecosystems can crash

• More intense storms and hurricanes• Spread of infectious disease (malaria)• "Tipping point"

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Factors that affect earth's temperature• Ocean-stores CO2 (less with increasing T)• Cloud cover

> absorb and release heat into troposphere> reflect sunlight

• Air pollutants> aerosols (size determines effect)

• Photosynthesis (net change in CO2 = 0?)• methane: swamps and methane hydrates

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Effects of Global Warming

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1. Melting ice and snow• less reflection of sunlight (positive feedback)• mountain glaciers-source of fresh water• melting land based ice (not floating sea ice)-raise

sea levels

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2. Rising Sea Levels• Predicted raise of 9-88cm in this century

> mostly from expansion of sea water• Threaten coastal estuaries, coral reefs, lowlands

and deltas• Floods barrier islands

> erosion> less protection from storms

• Saltwater intrusion• Islands?

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3. Changing Ocean Currents

• Distributes heat, stores CO2 in deep sea

• Cooling in some regions

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4. Warmer, more acidic seas• reduced current = reduced upwelling

> decrease 1º productivity> *positive feedback

• More CO2 --> more dissolved as carbonic acid> reduces carbonate ions (needed by corals, other

organisms with shells)

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5. Changes in precipitation and weather extremes• Affect hydrologic cycle

> agriculture> expanding deserts> droughts in one area, more severe flooding/

precipitation in others

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6. Changes in biodiversity• Allow some species to expand ranges (warmer)• 1 million face premature extinction?

> narrow, specialized niche> narrow range of tolerance

• Ecosystems most likely dirupted> coral reefs> polar seas> coastal wetlands> tundra> high-elevation mountain tops

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7. Agriculture and fish stocks• How will climate change affect agriculture?

> Shift north (more rain, warmer)> Overlap of soil fertility and climate (?)

• Decrease in snowfall/glaciers on mountain tops reduce water available for irrigation

• *Predicted decline in agricultural productivity in tropical/subtropics region> *world's poorest

• Fish stocks-affected by changes in sea levels> coastal wetlands> aquaculture ponds

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8. People?• Heat stress• Tropical infectious disease• Allergens• Flooding/droughts

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act nowwait-and-see

adaptationmitigation

Climate change: What do we do?

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*these solutions are expensive

*unknown consequences (ocean)

Mitigation Solutions• reduce fossil fuel use

> improve efficiency> shift from fossil fuels to renewable energy

source> Reduce population> reduce poverty

• Sequester carbon> plant more trees> soil sequestration> no-till cultivation (reduce CO2 N2O release)> inject into coal seams or ocean

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Government Roles• Carbon taxes/energy taxes• Subsidies for efficiency, renewable energy, carbon

sequestration, sustainable agriculture• Phase out subsidies for fossil fuel, nuclear power,

unsustainable agriculture• Technology transfer

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Kyoto Protocol• International meeting: treaty to help slow global

wamring• 38 participating developed countries (US backed out

in 2001) to cut emissions of CO2, CH4, N2O, HFCs, PFCs, SF6 > developing countries exempt for economic

development• Goal: Reduce GHGs emission by 5% of 1990 levels

in commit period from 2008-20012 in developed countries

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Kyoto Protocol: How to achieve reductions?• Implement national policies on

> efficiency> sustainable agriculture> research and use of renewable energy> reduce tax exemptions/subsidies to sectors

that emit GHGs> reduce methane--recover and use as energy

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Kyoto Protocol GHG Emission Targets + Mechanisms• GHG emission targets for countries that range from

-8% to +10% of 1990 GHG emission levels• Can reach by

> Increasing sinks (reforestation, planting new forests)

> Actually cutting GHG emission• Other Mechanisms

> Emission Trading> Clean Development > Joint implementation

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Kyoto Protocol: Emission Trading• Can sell spare emission units to countries that are

over their targets• Can sell:

> emission units> removal units from reforestation> emission reduction unit by a joint

implementation project> certified emission reduction from clean

development mechanism project

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Kyoto Protocol: Clean Development Mechanism• Countries can partly reach GHG emission reduction

by sponsoring ($$$) GHG-reducing projects in developing countries

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Kyoto Protocol: Joint Implementation• A country can invest in a foreign country also

under the protocol to either remove emissions there or increase carbon sinks

• *foreign investment + technology transfer

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Kyoto Protocol a Success?

Of the 37 countries that stuck through, saw 16% reduction in GHG emission.

However, global GHG emission continues to rise.

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Other efforts by nations/companies to reduce energy waste and reduce greenhouse gas emission.• EU• Japan• Canada• China• California• Companies: DuPont, IMB, Toyota, GE, etc.

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Preparing for global climate change

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Ozone Layer• lower stratosphere• keeps 95% UV radiation from reaching earth• Thinning (depletion)

http://www.epa.gov/ozone/science/sc_fact.html

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Ozone Depletion• CFC* (freons)

> coolants, propellants, cleaners, fumigants• halons• HBFCs• CH3Br

• HCl• CCl4• CH3CCl3 (methyl chloroform)

• n-propyl bromide• hexachlorobutadiene

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Annual Variation in Ozone Levels• Thinning over Antarctica during October and

November• Winter--winds create a polar vortex

> water droplets turn in to ice, surface coated with CFC and other chemicals in stratosphere

• When vortex breaks up--ozone depleted air flows northward to Australia, New Zealand, South America, South Africa

• Same phenomena in Arctic February-June

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Less ozone = increased UV exposure• Increased human health problems• Reduced productivity (crops, seafood, trees)• Disrupted wildlife (health problems, population of

phytoplankton)• Increased pollution (acid deposition,

photochemical smog, degraded chemicals)• Global warming accelerated

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Protecting Ozone Layer• stop using ozone depleting chemicals

> especially CFCs and their substitutes• International cooperation

> Montreal Protocol (cut CFC emission)> Copenhagen Protocol (ODC)

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Current Events Activity

In groups of 3-4, share your articles. Then, pick one that you think is the most interesting/exciting/controversial/etc.

With your group, come up with 2 discussion questions and 3 review questions related to your article. You will lead a 5 minute discussion/review of concepts.

When we are done, you will turn in all of your q's + all of your group's article summaries stapled together.

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