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Global warming
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Global warming
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Global warming
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978-1-4730-1923-2 (.kdl)
978-1-4730-1155-7 (.epub)
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Contents

Introduction

Learning outcomes

1 Natural climate change?

2 A 4.6 billion-year history

3 Recorded temperatures

4 Further reading

5 Human influence?

6 Further reading

7 Climate models

7.1 Climate models

7.2 Comparing modelled and observed temperature

7.3 Running the models forward

7.4 Closing thoughts

Conclusion

Keep on learning

References

Acknowledgements
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Introduction
This course provides an introduction to global warming. We will be
considering the history of global warming by looking at the pattern
of ice ages and analysis of recorded temperatures. We will aim to
gather meaningful information from this data. We will briefly assess
the impact and influence of humans on global warming and, finally,
we will examine climate models and how to predict future changes.
This OpenLearn course provides a sample of postgraduate study
in Education, Childhood & Youth qualifications.
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Learning outcomes
After studying this course, you should be able to:

understand the current evidence for global warming

model and apply the techniques of ‘measuring’ the
Earth's temperature

understand the current warming in relation to climate
changes throughout the Earth's history

explain factors forcing climate change, and the extent
of anthropogenic influence

assess the ‘best predictions’ of current climate models.
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1 Natural climate change?
The chart below shows a record of the global mean surface
temperature of the Earth compiled for the past 140 years. Clearly
there is an upward trend, but what does a chart like this really
show?
Figure 1 Chart of variations in the Earth's surface temperature
To understand what the chart shows, it is necessary to take the
‘long view’, looking back through the whole history of the Earth.

How can we know the temperature of the planet over
time-scales of billions of years?
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
Is this current warming part of the Earth's natural
temperature variation?

What factors affect and force changes to the global
temperature, and to what extent are these being
affected by human activity?

What are the best predictions for change over the next
100 years?
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2 A 4.6 billion-year history
Climate change is a natural process of warming and cooling that
has occurred all through the Earth's history. Throughout geological
time there have been ‘hot-house’ periods and ice ages. In order to
understand the current situation, it is necessary to have some
sense of context and perspective, from historical and geological
time-scales. The document below shows a chart showing a
generalised temperature history of the Earth.
Click on the link below to see the chart
Temperature history
We are currently enjoying an interglacial period of an ice age that
began approximately two million years ago. (Ice ages are
composed of colder ‘glacial’ and warmer ‘interglacial’ periods.)
This is at least the seventh ice age in the Earth's 4.6 billion-year
history.
During the Cretaceous (65–147 Ma) the whole Earth was up to
+15°C (warmer than at present, with tropical forests covering
Antarctica, whereas during the Quaternary (~2 Ma) ice sheets
spread across much of Europe and the mean surface temperature
was up to (5 °C colder than at present. The range of these
changes is much greater than the observed increase in
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temperature over the past century (+0.6 ±0.2 °C) and predictions
for the next hundred years (+3 ±1.5 °C).
Click on the link below to read ‘Glaciers past and present’
Glaciers past and present
Click on the link below to read ‘Pollen diagrams and ancient
climates’
Pollen diagrams and ancient climates
Activity 1 Past temperatures: before
measurement, before people
Measuring temperature is a relatively recent affair. Galileo Galilei
invented his thermometer in 1597, but the longest running record
of surface temperature to the present day only dates from 1815.
For periods prior to these measurements, our understanding of the
history of climate change is inferred from geological evidence,
primarily:
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
Glaciation (showing that much of the northern
hemisphere was covered in ice, some 18 000 years
BP).

Fossilised pollen (showing that over the past 140 000
years, the mean temperature has varied by almost 15
°C).
Prepare a brief (no more than five minutes) presentation on the
information concerning climate change provided by either
glaciation or the pollen record. The presentation should close with
3–7 key ideas to explore. Two resources are provided to help you
do this: ‘Glaciers past and present’ and ‘Pollen diagrams and
ancient climates’. To access these resources, click on the "view
document" links above.
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3 Recorded temperatures
Analyses of over 400 proxy climate series (from trees, corals, ice
cores and historical records) show that the 1990s was the warmest
decade of the millennium and the 20th century the warmest
century. The warmest year of the millennium was 1998, and the
coldest was probably 1601. (Climatic Research Unit, 2003)
Throughout historical times, fluctuations in the Earth's mean
temperature have been recorded. During the seventeenth century,
the Thames periodically froze over during winter and mini-glaciers
were present in the North West Highlands of Scotland. More
recently, the 1990s included some of the hottest years ever
recorded in the British Isles, and 10 August 2003 was the hottest
day ever on record. An annual temperature record for central
England has been constructed, beginning in 1659.
Click on the link below to open a chart of central England
temperatures from 1659 to 1995
England temperatures from 1659 to 1995
Look at the chart in the above document. How do the readings for
1660–1700 compare to 1960–2000?
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You have probably noticed that in the first period most points were
below the mean, but in the latter period, most were above it.
Because the data are so scattered, some method is required for
seeing the overall trend more clearly. A single ‘line of best fit’
(regression analysis) is not appropriate, as it hides small-scale
variations that may be significant. Such changes in the recorded
temperatures are manifest throughout the British Isles, resulting in
changes to natural fauna and flora. These changes are also having
local economic impact, such as the northwards spread of
vineyards in the UK. (At the time of writing I believe the most
northerly vineyard in the UK is in Swillington, near Leeds.)
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4 Further reading
For information on changes to flora, click on Science magazine.
For changes to fauna, and economic effects, go to Information
Sheet 4, or for the paper quoted at the top of the screen,
Information Sheet 1, both at Climatic Research Unit.
Click on the link below to open the data-smoothing information
Data-smoothing
Click on the link below to read about working with global mean
surface temperature
Working with global mean surface temperature
Activity 2
There are two key ways of getting meaningful information out of
climatic data sets:

data-smoothing;
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
working with global mean surface temperature –
GMST.
Click on the "view document" links above to read explanations of
these techniques. Consider how you might model these two
processes with students.
You may want to consider:

using a maximum/minimum thermometer over 24-hour
periods;

data-logging temperature over a longer period;

using a rain gauge;

comparing your own data with data from the
Meteorological Office.
(The Meteorological Office provides monthly rainfall
and mean monthly temperature data from 1961 to the
present. Click on the link Meteorological Office to
access their site: scroll down to ‘Past’ and click on
‘Monthly information’ to look at the statistical details.
Sketch out an outline of a teaching sequence that explores datasmoothing and the concept of GMST.
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5 Human influence?
Evidence suggests that global temperature is beginning to rise.
There are several factors that could cause this. Only one is
affected by human activity.
Click on the link below to view a chart showing the rates of energy
gain and loss by the Earth's surface and atmosphere
Energy gain and loss
Up to this point we have been primarily concerned with evidence
and trends, with ‘what has happened’. This sort of analysis does
not tell you ‘why’ something happened. To understand ‘why’, we
need some sort of explanatory model that works on a global scale.
The starting point of ‘why’ for climate change, is to consider energy
flows in the climatic system. Click on the link above to see a chart
showing the rates of energy gain and loss by the Earth's surface
and atmosphere.
Note that even though the arrows starting and stopping in the
atmosphere do so in small region in the centre, the atmospheric
energy gains and losses that they represent take place throughout
the atmosphere. 100 units represent the rate at which solar
radiation is intercepted by the Earth. The width of each arrow is
proportional to the rate of energy transfer.
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If you would like a full explanation of the energy flows in the
diagram, click on the link below to read more.
What determines the GMST
Activity 3 explores the possible causes that may be disturbing the
equilibrium of such a model, and the evidence of human influence.
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6 Further reading
The models being used in research take such simple energy flows
and increase the ‘granularity’ of the components used, to build
complex time sequences.
You may like to see Information Sheet 8 at the website of the
Climatic Research Unit for a summary of how these have
developed.
Click on the link below to see charts mentioned in the activity
below
Human influence on the atmosphere
Activity 3
Click here to read Information Sheet 2, ‘Causes of climate change’,
from the website of the Climatic Research Unit.
Which of the potential causes are influenced by human activity?
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Click on the "view document" link above and compare the charts
for greenhouse gases (carbon dioxide, nitrous oxide and methane)
and temperature over the last 1000 years.

Discuss the key features and implications of these two
sets of information.

Compare the radiative forcing for the human
influences – what does this suggest?
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7 Climate models
7.1 Climate models
To understand climate change it is necessary to construct climate
models, to explore and predict interactions between different
factors. Models are tested for accuracy against known sets of data,
before being run forward to predict future changes.
7.2 Comparing modelled and observed
temperature
The IPCC comparison between modelled and observed
temperatures since the year 1860 is shown in the three charts
below
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Figure 2 Chart showing natural forcing
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Figure 3 Chart showing anthopogenic forcing
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Figure 4 Chart showing both natural and anthopogenic forcing
It is clear from these charts that both natural influences and
anthropogenic forcing are required to explain the recent rises in
temperature.
7.3 Running the models forward
What happens when the models are run forward? It depends upon
the models used and the scenarios they are asked to run. It seems
almost certain, however, that there will be increases in the global
mean surface temperature, to the order of +1.5 to +4.5 °C (–
possibly more, according to some models and scenarios.
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These changes are predicted to be associated with increases in
sea level, changes to weather conditions (e.g. more regular and
violent winter storms in the UK) and changes to the distribution of
habitats and their associated organisms.
The current predictions for the global climate in the twenty-first
century are shown for a range of scenarios and models in the
charts below. (Chart (a) shows the range of scenarios for CO2
emissions; charts (b) and (c) show the corresponding predictions
for temperature change and rise in sea level.
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Figure 5 Chart a showing nitrous oxide concentration
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Figure 6 Chart b showing temperature change
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Figure 6 Chart c showing change in sea level
7.4 Closing thoughts
Of course, doing anything about this needs scientific evidence and
understanding, but it also requires social, economic and
technological changes, which can only be achieved through
political will. If you want to explore some of the broader context, a
good place to start would be the New Internationalist issue 357,
‘The Big Switch: Climate Change Solutions’ at New
Internationalist.
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Faced with the sort of predictions climatologists are making, is it
sufficient for science teachers to stop at the ‘science’, or should we
be tackling some of these broader issues in schools?
If you want to find out more, the Hadley Centre is the UK's
foremost climate research centre and provides a lot of useful
information, as does the Intergovernmental Panel On Climate
Change at IPCC.
If you wish to view tis simulation in a new window click on 'Launch
in separate player'
Interactive content is not available in this format.
Activity 4
To help you understand some of the key factors in climate
modelling, click on the link above to work through a simplified
simulation.
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In reality, climate modelling is extremely complex, because all the
variables are not known. The ability to develop mathematical
models of climate change is constantly improving, but there are
still many competing models, each making different predictions of
how the climate will change. All models, currently, show a
significant increase in the global mean surface temperature
attributable to human influences.
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Conclusion
This free course provided an introduction to studying Education,
Childhood & Youth qualifications. It took you through a series of
exercises designed to develop your approach to study and
learning at a distance and helped to improve your confidence as
an independent learner.
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References
Climatic Research Unit (2003) Information Sheets at
http://www.cru.uea.ac.uk
New Internationalist (2003) ‘The Big Switch: Climate Change
Solutions’, June, issue number 357.
The Open University (1998) S103 Discovering Science, Block 2 ‘A
Temperate Earth?’, Milton Keynes, The Open University.
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Acknowledgements
This unit was prepared by Tom Power with guidance from Dr
Arlene Hunter.
Tom Power is a lecturer in science education at The Open
University. His research interests include teacher education in the
global south (www.open.ac.uk/deep) and the CASE intervention.
He has been a teacher and an advisory teacher in East Sussex
and a specialist adviser to the TTA teacher research panel.
Dr Arlëne Hunter, Staff Tutor in Science in Ireland, The Open
University, is responsible for the management of the science
programme across Ireland and contributes to various
undergraduate earth and environmental science courses. Her
research is divided between geochemistry and enhancing the
learning and teaching experience for students and staff.
This unit draws upon many sources, but has been developed
primarily from the Open University Science short course (1998)
S103 Discovering Science: 2 A Temperate Earth, Milton Keynes,
The Open University.
Except for third party materials and otherwise stated (see terms and
conditions), this content is made available under a Creative
Commons Attribution-NonCommercial-ShareAlike 4.0 Licence.
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Grateful acknowledgement is made to the following sources for
permission to reproduce material in this unit:
Course image: Michael Himbeault in Flickr made available under
Creative Commons Attribution 2.0 Licence.
Charts of: variation of the Earth’s surface temperature, carbon
dioxide, nitrous oxide, methane, natural forcing, anthropogenic
forcing, natural and anthropogenic forcing, carbon dioxide
emissions, temperature change, rise in sea level: copyright ©
IPCC.
Extracts from the Open University course S103 Block 2 ‘A
temperate Earth?’
Figures 3.3 and 3.5 courtesy of Tony Waltham;
Figure 3.4 Landform Slides;
Figure 3.6a The British Geological Survey, copyright © NERC, all
rights reserved
Figure 3.7 John, B. S. (1977) The Ice Age, HarperCollins
Publishers Ltd
Figure 3.10 courtesy of C. Turner
Figure 3.11 courtesy of C. J. Hawksworth
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Figures 3.12 and 3.13 West, R. G. (1977) Pleistocene Geology
and Biology, 2nd edition, p. 362, reprinted by permission of
Addison Wesley Longman Ltd
Figure 3.14 reprinted with permission from Nature, 281, 18
October 1979, p. 559, Woillard, G. (1979) ‘Abrupt end of the last
interglacial S.S. in North-East France’, copyright © 1979 Macmillan
Magazines Limited
Figure 3.15 reprinted with permission from Nature, 338, 23 March
1989, p. 312, Guiot, J., Pons, A., de Beaulieu, J. L. and Reille, M.
(1989) ‘A 140,000-year continental climate reconstruction from two
European pollen records’, copyright © 1989 Macmillan Magazines
Limited
Figure 3.16 Brown, G. C, Hawkesworth, C .J. and Wilson, R. C. L.
(1992) Understanding the Earth, 2nd edition Cambridge University
Press.
Figure 2.10 Parker, D. E. et. al. (1966) ‘A new daily Central
England temperature series, 1772–1991’, International Journal of
Climatology, 12, Royal Meteorological Society.
www.meto.gov.uk/climate/uk/2003/june.html
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video model of changes in the temperature of the Earth: © Crown
Copyright. Reproduced with the permission of the Controller of Her
Majesty’s Stationery Office.
Every effort has been made to trace all the copyright owners, but if
any has been inadvertently overlooked, the publishers will be
pleased to make the necessary arrangements at the first
opportunity.
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