Summary of topic 6

Topic 6 The Issue of Global Warming

The Role of Greenhouse Gases• The average temperature on the Earth is 15oC• Incoming radiation is low wavelength/ high energy• The average temperature is maintained by atmospheric

gases trapping or reflecting a fraction of the outgoing (long wavelength/ low energy) heat radiation

• These (greenhouse) gases include:– Water vapour (H2O)

– Carbon dioxide (CO2)

– Methane (CH4)

– Ozone (O3)

– Nitrous oxide (N2O)

The Role of Greenhouse Gases

Without these naturally occurring greenhouse gases, the average temperature of the Earth would be approximately -15oC

Change in Global Temperature Over Time

This data is taken from measurements of the concentration of the oxygen isotope 18O in air bubbles trapped in rock and ice. This concentration is temperature dependent but can only be used to give an indication of temperature change rather than a measurement of temperature itself

Change in Global Temperature Over Time

Change in Global Temperature Over Time

The Role of Carbon Dioxide

• Earth’s atmosphere today ≈ 380 ppm CO2 (0.038%)

• Early Carboniferous Period ≈ 1500 ppm CO2

• Middle Carboniferous Period ≈ 350 ppm CO2

• Earth’s atmosphic temperature today 15oC• Early Carboniferous Period 20oC• Middle Carboniferous Period 12oC

Over the last 600 million years, only the later Carboniferous Period and the present age (the Quaternary Period) have had CO2 levels less than 400 ppm. This means that the temperature of the Earth today is considerably cooler than for most of geological history.

359 mya

300 mya

The Role of Carbon Dioxide• Levels of CO2 are currently increasing

• CO2 levels have risen from 280 ppm in 1850 to 380 ppm today• It is widely accepted that this is due to anthropogenic activity

although natural factors may also influence it

The Role of Carbon Dioxide

• Factors affecting CO2 concentration:

– Industrialisation and burning of fossil fuels– Deforestation (particularly rainforest)

– Volcanic activity– Sunspot activity

Anthropogenic factors

Non-anthropogenic factors

Do you think there is a correlation between the increasing output of carbon dioxide due to anthropogenic activity and increasing global temperatures? Can we be certain that the first is responsible for the second?

Anthropogenic Factors• Burning of fossil fuels

– Coal, oil and natural gas

• Deforestation– Breakdown of organic matter in biomass and soil– Burning of biomass– Reduction in photosynthesis

• Cattle ranching– Cow farts

• Rice farming in padi fields– Anoxic conditions allow growth of methanogens

• Use of fertilisers– Breakdown of nitrogen-rich compounds

CO2

CH4

N2O

Global Greenhouse Gas Emissions in 2000

other gases

carbon dioxide

methane

nitrous oxide

9%1%

Anthropogenic Factors

74%

16%

Sources of Carbon Dioxide Emissions

oil and petroleum

coal

deforestation

natural gas

other sources

25%

3%

Anthropogenic Factors

26%

31%15%

The proportions vary from country to country depending on its economy and energy demands

The Effects of Global WarmingFeature Effect

Environmental EffectsIce and snow Retreat of polar icecaps and glaciers

Coastline Increase in sea level and coastal flooding

Water cycle Increased flooding

Ecosystems Change in biome and species distribution

Societal EffectsWater resources Severe water shortages (conflict)

Agriculture Shifts from drought affected areas

Coastal settlements Shifts due to storms and flooding

Human health Increased outbreaks of disease

The Effects of Global Warming

The Effects of Global Warming

• Biome shifts– Models suggest biomes will shift north/south from the

equator and vertically to higher ground. – Low-lying biomes such as mangroves may be lost

completely• Species changes– Climate change in the past has been slow and allowed

animals and plants to adapt– There may be migrations, but many obstacles (some

anthropogenic) and lack of suitable habitats may lead to mass extinctions

– Increased temperature may lead to spread of pests and tropical disease vectors

The Effects of Global Warming

• Weather– Effects on weather patterns and rainfall are

unpredictable– Storms are expected to increase in intensity

• Agriculture– Increasing drought events would reduce crop yield and

affect farmers’ ability to irrigate (especially in LEDCs)– Suitable areas for crop growth would be expected to

move north/south from the equator– Farmers may be forced to change the crops they

cultivate

The Effects of Global Warming

• Tourism– Summer seasons may be extended– New coastal resorts may develop– Lack of water resources may be a problem in some– Winter sports may be curtailed and resorts closed

• Social Issues– Conflicts over resources (especially water) may be

expected to increase– Economic changes may occur– LEDCs will be less able to cope than MEDCs– Low lying areas (especially in LEDCs – with poor

infrastructure) will be prone to coastal flooding

Possible Positive Feedback Mechanisms1. Melting of polar

ice may result in less white areas on the Earth’s surface– This may lower the

Earth’s albedo, the amount of incoming radiation reflected into space

– This may lead to further temperature rises

Possible Positive Feedback Mechanisms

2. The melting of permafrost in taiga and tundra biomes may release methane from rotting vegetation which is currently trapped

Possible Positive Feedback Mechanisms

3. Increased temperature may increase decomposition rates therefore releasing more CO2 into the atmosphere

4. Deforestation may lead to warming and drying of the climate, leading to further loss of rainforest

5. Increased forestation in higher latitudes may further decrease albedo

Possible Negative Feedback Mechanisms

1. Increased evaporation in equatorial latitudes may lead to more water being carried through the Ferrel and Polar Cells, leading to increased snowfall at the poles and restore the Earth’s albedo

2. Increased levels of CO2 may lead to increased rates of photosynthesis, which in turn would lower the concentration of atmospheric carbon

Possible Negative Feedback Mechanisms

1. Increased evaporation in equatorial latitudes may lead to more water being carried through the Ferrel and Polar Cells, leading to increased snowfall at the poles and restore the Earth’s albedo

2. Increased levels of CO2 may lead to increased rates of photosynthesis, which in turn would lower the concentration of atmospheric carbon

Pollution Management Strategies to Reduce Global Warming (Policy)

• Control the release of greenhouse gases• Reduce the rate of deforestation• Increase tree planting programmes• Develop renewable energy resources• Reduce car use and improve public transport• Set national limits on carbon emissions• Use carbon credits and carbon trading to offset CO2

emissions• Develop methods to sequester carbon from the

atmosphere (biological and chemical)

Pollution Management Strategies to Reduce Global Warming (Individuals)

• Grow your own food• Buy locally grown produce• Use energy efficient products (e.g. light bulbs)• Reduce heating your house/ improve insulation• Use less electricity and unplug appliances• Turn off lights when not in use• Reduce use of air conditioning and refrigerants• Don’t waste water (take showers instead of baths)• Walk and use a bike/ use cars less/ use public transport• Use biofuels• Eat less meat• Get involved in public education/ activism

The Kyoto Protocol

• In 1997, 183 countries signed this agreement to try to keep global greenhouse gases at a stable level

• It came into force in 2005• Each country’s emissions were divided into credits and

they were allowed to buy and sell them• Countries are also able to offset their emissions by

planting trees (an alternative to buying carbon credits)• The US and Australia signed but refused to ratify the

Kyoto Protocol• Canada signed and ratified it, but has since withdrawn

from its obligations

The Future of the Kyoto Protocol

• The original agreement was due to end in 2012

• Representatives of the signatories met in December 2012 to discuss its future

• It was extended until 2020. Richer nations agreed in principle to compensate poorer nations

http://www.youtube.com/watch?v=NAsGnGWZS1M&list=PLITAq0aJinsQLtj9dV3Q1tHoSIK76sczWhttp://www.youtube.com/watch?v=xpiM2LuK4O4&list=PLITAq0aJinsQLtj9dV3Q1tHoSIK76sczW

The Problems of Debating the Issue• It is a problem on a global scale• It includes natural and anthropogenic factors• The mechanisms (including feedback) are not well

understood• The processes are occurring over the long term and the

impacts may not have occurred yet• Many people involved on both sides are affected by vested

interests (consciously and unconsciously)• Much of the evidence and forward-planning is based on

climate models which have considerable inherent uncertainty• Actions are likely to have huge cost implications for a large

proportion of the human population• A huge amount on information is now available to everybody

(scientists and non-scientists) and much of it is misleading

The Main Players

• Al Gore– Former US vice president

and presidential candidate

– Winner of the 2007 Nobel Peace Prize

– Writer of the book and film An Inconvenient Truth

http://www.youtube.com/watch?v=splKGWuErnM

The Main Players• Bjorn Lomborg– Danish economist– Writer of the book and film The

Sceptical Environmentalist: Measuring the Real State of the World

– Accepts that human activity may be affecting climate but refutes suggestions that this should be something that affects the global economy

– Opposes the Kyoto Protocol and the idea of carbon tax

http://www.youtube.com/watch?v=Dtbn9zBfJSs

The Main Players

• Martin Durkin– UK film-maker– Maker of the documentary

The Global Warming Swindle– Vehemently opposes the

idea that climate change is anthropogenic

– States a belief that temperature affects CO2 concentrations rather than the reverse

http://www.youtube.com/watch?v=lIjGynF4qkE

http://edroness.blogspot.mx/2014/05/the-great-global-warming-swindle.html

The Main Players• Sir Nicholas Stern

– Former vice-president of the World Bank and current president of the British Academy

– Author of The Stern Review on the Economics of Climate Change for the British government

– Believes that anthropogenic climate change poses a series threat to global economic stability and that the precautionary principle is warranted

– Believes that carbon taxation and international agreements are a sensible way to approach the problem

http://www.youtube.com/watch?v=pqLROIKWM2s

Questions

1. What are the main greenhouse gases?2. What role do they play in maintaining global

temperature?3. Describe 4 different ways in which human activities

affect the concentration of greenhouse gases in the atmosphere

4. Describe and evaluate strategies to reduce global warming

5. Evaluate 4 different perceptions of the issue of global warming