4.3 Technical and behavioural actions

The numbers generated by the carbon calculator use a computer model based on some of the best information available. However, as I mentioned earlier, the results are not exact because calculators typically require you to enter broad categories of information about yourself and your household. And there are always uncertainties about some of the data on which the calculator is based. Nevertheless, the calculator allows you to explore the important actions needed to lighten your carbon load and
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3 How heavy is your footprint?

You've seen that individual and household carbon footprints vary widely both within and between countries. So, in this section you'll be working out your own carbon footprint using the computer-based calculator linked in the box below. This is the Quick version of this calculator. A more detailed and complete version is available when formally studying the Environment: journeys through a changing
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2.3 International comparisons of carbon footprints

You've seen that the carbon footprint of an individual or household is a simple idea, but calculating it can be quite complicated. It depends on whether you count only CO2 or include other greenhouse gases; whether you count only the emissions generated within a country or include imports and exports; and whether you count emissions from government activities as part of a citizen's carbon footprint.

This means that international comparisons can be difficult and so are usually
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1.1.2 The carbon footprint boundary

Depending on where you draw the boundary, the carbon footprint can apply to an individual person, a household, an organisation or event, a product, a city, region or country, or the whole world. I'll mainly be considering the footprints of individuals, households and the countries they occupy.

But even then the boundary needs to be defined carefully. Sometimes the carbon footprint is taken to mean the individual's or household's direct CO2 emissions, main
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References

Edwards, P. N. and Schneider, S. H. (2001) Self-governance and peer review in science-for-policy: the case of the IPCC Second Assessment Report, in Miller, C. and Edwards, P. N. (eds) Changing the Atmosphere: Expert Knowledge and Environmental Governance. Cambridge, MA: MIT Press. Available from: http://stephenschneider.stanford.edu/Mediarology/Mediarology.html (accessed 10 May 2007).
IPCC (2000) Land Use, L
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2.8 End of unit question

Question 12

The writer and campaigner George Monbiot wrote the following (in The Guardian Weekly, 10 February 2000): ‘Every time someone in the West switches on a kettle, he or she is helpting to flood Bangladesh’. What is th
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2.6.1 Weighing up the evidence: the full cast of suspects

Figure 36 (again adapted from the TAR) takes your thoughts on Question 11 on a stage. It gives estimates of the cumulative effect since pre-industrial times of the various climate change agents, with the contributions expressed in terms of radiative forcing. Note that the figure also includes yet another device for communicating the IPCC's confidence in a particular finding – an indication of the ‘level of scientific understanding’ that accompanies each estimate. This reflects the autho
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2.5.2 Environmental indicators

The notion of a link between climatic conditions and the behaviour of plants and animals (e.g. the growth of trees or coral) and the composition of natural communities or ecosystems (the type of vegetation in a given area, say) is fundamental to the use of proxy data to reconstruct past climates. Some examples of biological responses to recent climate change were included in Box 9. Here we should be wary of jumping to conclusions. Such changes involve complex living systems that can respond i
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2.2.1 Long-term rhythms in the climate

The instrumental record referred to above is based on direct temperature measurements (using thermometers), and extends back only 150 years or so. Temperatures further back in time are reconstructed from a variety of proxy data. These include historical documents, together with natural archives of climate-sensitive phenomena, such as the growth or retreat of glaciers, tree rings, corals, sediments and ice cores (see Author(s): The Open University

2.2 Records of the Earth's temperature

To put the temperature records reported by the IPCC in context, we start with a longer-term geological perspective on the Earth's GMST.


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2.1 Preamble

Here are some quotes from the ‘Summary for Policymakers’ (SPM) included in the report from the scientific working group in the IPCC TAR (IPCC, 2001a):

  • The Earth's climate system has demonstrably changed on both global and regional scales since the pre-industrial era, with some of these changes attributable to human activities.

  • Globally, it is very likely that the 1990s was the warmest decade and 1998 the warmest year in the instru
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1.7 Summary

  1. Figure 12 summarises the ways in which the Earth's surface and atmosphere gain and lose energy. The main points are as follows:

     

    • A proportion (the planetary albedo) of the incoming shortwave radiation from the Sun is reflected (or scattered) directly back to space, mainly by clouds and the Earth's surface (especially snow and ice cover), but also by aerosols (e.g. dust, salt particles, etc.). Most of the re
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1.6 The human impact on the atmosphere: the coming of the industrial age

There is no doubt that CO2 is accumulating in the atmosphere. The record from Mauna Loa charts a continuing rise in CO2 concentration since measurements began in 1958, when the level was 315 ppm; the value had reached about 370 ppm by the end of the 20th century, and hit more than 378 ppm in 2004. Important as changes in atmospheric CO2 undoubtedly are (see below), we need to be aware that this is not the whole story of human-induced greenhouse forcing. In par
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1.5 ‘Radiative forcing’ as an agent of climate change

Since its first major report in 1990, the IPCC has used the concept of ‘radiative forcing’ as a simple measure of the importance of a potential climate change mechanism. The basic idea is straightforward. Any factor that disturbs the radiation balance at the top of the atmosphere has the potential to ‘force’ the global climate to change: it will either warm up or cool down until a balance is restored. The perturbation to the energy balance of the whole Earth-atmosphere system i
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1.3.4 The role of convection in the atmosphere

We come now to our final refinement to the simple picture in Figure 7. Recall that the troposphere is heated from below, with temperature then falling with increasing altitude. This situation sets the scene for the onset of convection – the bulk flow or circulation of a fluid driven by differences in temperature. Convection in the atmosphere plays a vital role in two further mechanisms – quite apart from the emission of longwave radiation – whereby energy is transferred from the
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1.3.3 The role of clouds

We have already identified one role that clouds play in the Earth's climate: they are highly reflective (Section 1.2.1). At any given time, about half of our planet is covered by clouds; the sunlight they reflect back to space accounts for about 55% of the total planetary albedo. However, clouds also absorb and re-emit outgoing longwave radiatio
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1.3.2 The fate of incoming solar radiation

Look back at Figure 7. In this schematic representation, what is the fate of incoming solar radiation?

Answer

It is either reflected back to space (31 units) or absorbed by the su
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1.3 Energy flows within the Earth-atmosphere system

Before we focus on the enhanced greenhouse effect, we need to refine the schematic representation in Figure 7 and draw in some of the other processes that influence the Earth's temperature – not only at the surface, but also at different levels within the atmosphere.


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1.2.2 Bringing in the atmosphere: the natural greenhouse effect

As a dam built across a river causes a local deepening of the stream, so our atmosphere, thrown as a barrier across the terrestrial rays, produces a local heightening of the temperature at the Earth's surface.

(Tyndall, 1862, quoted in Weart, 2004)

Thus, writing in 1862, John Tyndall (Figure 6) described the key to our modern understanding of why the Earth's surface is so much warmer than t
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1.2.1 Heating and cooling the Earth: the overall radiation balance

The Sun emits electromagnetic radiation with a range of wavelengths, but its peak emission is in the visible band – the sunlight that allows us to see. The wavelength of radiation has important climatic implications, as we shall see shortly. For now, we are mainly interested in the overall rate at which energy in the form of solar radiation reaches the Earth.

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