3. Global Warming Revision

(1)

Global Warming

a. Understand the greenhouse effect and its

importance in maintaining the earth’s temperature b. To recall the Carbon cycle and understand its

importance in determining atmospheric carbon dioxide levels

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GLOBAL WARMING

• _{The greenhouse effect}

• _{The cause of global warming}

• _{Evidence for global warming}

• _{Effects of global warming}

• _{Models of global warming}

• _{Describing the data}

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The Greenhouse Effect

• _{Carbon dioxide, methane and water vapour}

are greenhouse gases present in the atmosphere

• _{they trap infrared radiation}

• _{which is reflected from Earth’s surface} (re-radiation)

• _{This causes the}_{mean temperature}_{of the}

(5)

Methane

• _{Methane is many times more potent as a}

greenhouse gas than carbon dioxide

• _{There are two main sources of methane:}

ruminant cattle and the action of anaerobic

bacteria that live in the soil of rice paddy fields.

• _{The number of cows and rice paddy fields have}

(6)

CAUSE

14 Outline the causes of global warming – including the role of

greenhouse gases (carbon dioxide and methane, CH4) in the greenhouse effect.

• _{Explain how increases in carbon dioxide and methane,}

released into the atmosphere, may be contributing towards the estimated changes in mean temperature shown in the graph.

1. Carbon dioxide and methane are greenhouse gases ; 2. they trap infrared radiation

3. which is reflected from Earth’s surface (re-radiation)

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EVIDENCE

18 Analyze and interpret different types of evidence for global warming and its causes (including records of carbon dioxide levels, temperature records, pollen in peat bogs and dendrochronology) recognizing correlations and causal

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Temperature records for the past 1000 years

• _{What evidence is there?}

• _{UK Met office has weather records dating back}

to 1869.

• _{Data from ships records go back to about 1750}

• _{To go back further than that data is taken from}

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Dendrochronology

• _{Dating past events using tree ring growth.}

• _{Trees increase in width by cell division. When the}

climate is favorable, they grow more and so the width of the tree ring is wider. Wider tree ring growth is therefore correlated with greater

photosynthesis which may have occurred due to higher temperatures. Tree rings can therefore be

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• _{If tree ring growth is similar in two different} areas during the same year, then we use this to show there was a general climate change.

• _{However, wider rings don’t necessarily mean}

warmer weather in the 2 areas: it could have been wetter, sunnier or more CO2 in the

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Coral Reefs

• _{Data from coral reefs can be used to}

determine sea temperatures. The corals take up different ratios of isotopes depending on the sea temperature.

• _{This information can be used to back up}

evidence from tree ring records. They have

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Limitations of using corals

• _{They only give information of climate in tropical}

regions of the world

• _{They only give information for the lifespan of the}

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Peat Bogs

• _{Peat bogs are made from partly decomposed}

plant material. The peat is acidic, cool and anaerobic so plant material does not

decompose. Pollen grains, moss spores and plant materials are preserved.

• _{Different plants thrive in different}

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Peat Bogs: spore and pollen analysis

• _{E.g. Some species of spaghnum moss indicate}

cool conditions

• _{Other species of spaghnum moss indicate}

warmer, drier conditions.

• _{Pollen from horse-chestnut trees indicates}

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Temp records for over 300,000 years: Ice

Cores

• _{Taken from the Antarctic – drill down into the ice and}

analyze the air

• _{The ratios of O18 to O16 in the air that is trapped in}

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Evidence for increasing CO

₂

levels

• _{Ice core data stretches back 400,000 years} • _{Air samples from an observatory in Hawaii –}

this data has been used to create the “Mauna Loa” curve.

• _{The air is sampled continuously at the top of 4}

towers. The air is relatively free from pollutants

• _{These measurements show an increase from}

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• _{Global warming may increase the temperature at the}

particular latitude the plant or animal lives at.

• _{The new temperature may be above the maximum to}

complete development

• _{The species will tend to move North to cooler regions} • _{There maybe a change in food source, predators or}

competition

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Plants Animals

Distribution of species

Plants move to cooler regions – but can not move as easily as animals

Animals in the Northern

hemisphere move further North. Others maybe able to colonize a bigger area.

Conditions maybe ideal of insect-borne diseases. Conditions maybe ideal for disease-carrying organisms.

Development of species

Plants may grow faster due to increased enzyme activity such as rubisco, meaning that photosynthesis is faster.

However, other plants may not be able to cope with the temperature increase, and if temperatures increase too much than their enzymes will denature

Embryos of some organisms such as reptiles are sensitive to

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Life cycles Affected at higher latitudes where there are seasonal cycles. Plants grow and flower earlier

Insects become active earlier in the warmth. Some birds are not able to adapt so quickly so may not have the insect supply they depend on to feed their chicks. By contrast some animals might be able to fit in more than one breeding cycle.

• The majority of the world’s plant and animal species are found in the tropics. Temperature conditions in the tropics vary very little over the year so many

species have little tolerance for temperature change.

• Experimental data suggest a change by one or two degrees may be fatal.

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MODELS

• _{19 Describe that data can be extrapolated to make} predictions, that these are used in models of future global warming, and that these models have

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Using existing data to predict the future

• _{We can extrapolate data on greenhouse gases and use}

them in models to predict what might happen to temperature levels.

• _{This data should ideally be used in conjunction with}

data from other sources

• _{There are many limitations – we do not know the} exact effect that CO2 can have on global warming. • _{Models can not take into account unknown factors}

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Why might the data not be enough to

predict future climate change

• _{Not enough data}

• _{Data only collected from a limited area}

• _{No way of confirming data}

• _{If there are fluctuations}

• _{Means may be poor representations of the}

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DESCRIBING DATA

• _{Do the fluctuations match?}

• _{Is one curve above the other?}

• _{Reference to a particular change - increase or} decrease

• _{Manipulation of data!}

• _{Comment on the range of the data – does the}

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REDUCING GLOBAL WARMING

• _{Using plants and crops to produce biofuels}

because they are carbon neutral. This is

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ISSUES WITH BIOFUELS

• _{Land has to be cleared using machinery powered by}

fossil fuels to grow plants for biofuels. This produces carbon dioxide.

• _{Decomposition of dead plant material after clearing}

area to produce biofuels produces carbon dioxide

• _{The land could have been used for food production}

so less food is produced

• _{Fertilizers are needed to grow the plants which can}

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20 Discuss the way in which scientific conclusions about controversial issues, such as what actions should be taken to reduce global warming or the degree to which humans are affecting global warming, can sometimes depend on who is reaching the conclusions.

• _{Actions that can be taken to reduce global}

warming: use of biofuels, wind power, nuclear power, solar power.

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Biofuels are considered to be carbon neutral. Suggest why the continued draining and clearance of peat lands may contribute towards global warming

even though they may be used to produce biofuels. (5)

• Biofuels are carbon neutral as when burnt they release carbon dioxide that was removed from the atmosphere through photosynthesis.

There is therefore no net increase in carbon dioxide in the atmosphere.

• Carbon in peat was trapped millions of years ago, and when peat land is cleared it released carbon dioxide which means there is a met

increase in carbon dioxide in the atmosphere. The removal of plants during clearance also reduced photosynthesis and more carbon

dioxide is released when fossil fuels are burnt when the machinery is used.

• _{Carbon dioxide is a green house gas that absorbs IR radiation reflected} from the earth’s surface and preventing the IR escaping into space

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Some Scientists do not agree that fossil fuels are causing global warming – why not.

• _{Carbon dioxide is produced by burning fossil fuels. However, there is}

no direct evidence that increased CO2 leads to global warming. CO2 is released due to other processes such as by removing carbon sinks

such as peat bogs leads to an increase in carbon dioxide. There are other greenhouse gases such as methane, water vapour and CFC. Methane is released from ruminant animals and paddy fields.

• _{There are natural cycles that may be involved in global warming such}

as the action of volcanoes and the amount of solar radiation from the sun.

• _{Scientists that say that fossil fuels are to blame may be biased if they}

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It can be argued ruminant animals should be given specific feeds to reduce methane release

• _{Carbon dioxide and methane are both green house}

gases. Green house gases absorb IR radiation

reflected from the earth. Less green house gas leads to a reduction in the green house effect.

• _{Methane has a greater green house effect than}

carbon dioxide. If there is less methane the earth’s temperature is less likely to rise reducing the