Module 5 – The Ethics of Climate Change


Ethics is the study of how we decide what is right and wrong, or what is morally good and what is morally bad.

Lots of attention has been devoted to the science and economics of climate change. But climate change is as much an ethical issue as a scientific or economic one.

Various parties to the debate − governments, industry representatives, environmentalists − often claim that certain proposals are ‘fair’ or ‘unfair’.

In doing so, they are making moral statements. But it is not always clear, even to those making the statements, what the moral basis is of their claims.

The following aspects of the debate on global warming have a strong ethical dimension:

  • Who should take responsibility for global warming?
  • Who will be most affected by climate change?
  • Which countries should do more to reduce their greenhouse gas emissions?
  • Do rich countries have an obligation to help poor countries deal with the effects of climate change?

In this unit, we will explore the ethical principles that help us answer these questions. Ethical questions are often also questions of rights. The United Nations Universal Declaration of Human Rights says:

“Everyone has a right to life, liberty, and security of person.”

If global warming leads to crop failures, loss of safe drinking water and civil strife then these rights will be jeopardised.

With rights go duties, so the current generation must protect the Earth, its life forms and its resources for future generations. This idea is expressed in the idea of intergenerational equity, or fairness between generations.

The principle of intergenerational equity states that the present generation should ensure that the health, diversity and productivity of the environment are maintained or enhanced for the benefit of future generations.

In short, each generation should leave the environment no worse off, so that the ability of future generations to provide for themselves is not damaged by depletion of resources or pollution of the land, water and atmosphere. In particular, loss of species is irreversible.

What are the main ethical issues associated with global warming?



Climate change, including global warming, sea-level rise and changes in weather patterns, is mainly due to the cumulative emissions over time leading to increased concentrations of greenhouse gases in the Earth’s atmosphere.

Each year, more greenhouse pollution is pumped into the atmosphere. Only some of it is soaked up by vegetation and the oceans, so the concentration in the atmosphere rises.

Industrialised countries − comprising Western Europe, Japan, the United States of America, Canada, Australia and New Zealand − are responsible for around 75 percent of the increase in greenhouse gases since pre-industrial times – see Figure 1.

Figure 1 Shares of cumulative CO2 emissions over 1850-2002

Burning large quantities of fossil fuels has powered their economic growth over the last 200 years, so in this sense, greenhouse pollution has been inseparable from growing rich.

The polluter pays principle is widely accepted as a guide to who should take responsibility for environmental damage.

The polluter pays principle says that the person or company responsible for causing the pollution, or environmental damage, should be responsible for cleaning it up.

So if a factory pollutes a river with toxic waste and causes health problems for people living nearby, it is only fair that those who own the factory should meet the cost of reducing or cleaning up the pollution.

This is the theme of the film Erin Brockovich starring Julia Roberts. The movie is based on the life of a legal clerk in California who mounted a great legal action against a big company which was contaminating the drinking water of residents.

The polluter pays principle also applies in the case of climate change.

However, the situation is changing. Some large developing countries − especially China, India and Brazil − have been overgrowing in recent years, and their greenhouse gas emissions have been growing too – see Figure 2.

Figure 2 - Seven biggest annual greenhouse gas emitters 2000

It is expected that the annual emissions from developing countries will soon exceed those of industrialised countries and China will soon leap-frog the United States as the world’s largest annual emitter.

However, it will be some decades before these developing countries are responsible for half of the increased concentrations of greenhouse gases in the atmosphere.

The amount of greenhouse pollution that each person is responsible for is another important figure with ethical implications. China’s total emissions are ten times bigger than Australia’s, but the average Australian is in charge of nearly ten times more greenhouse pollution than the average Chinese (and is ten times wealthier).

In fact, Australians have the highest level of greenhouse pollution per person of all industrialised countries. Each person in China is responsible for around three tonnes of greenhouse gas emissions each year, and each person in India for around one tonne. Each Australian is responsible for around 27 tonnes.



Rich countries like Australia have been the main beneficiaries of increased greenhouse gases in the atmosphere because they have been able to industrialise by burning fossil fuels.

However, developing countries will experience more of the damage from global warming.

For example:

  • In Africa by 2020, between 75 million and 250 million people are projected to be exposed to increased water stress due to climate change;
  • In many parts of Africa, climate change is expected to reduce agricultural production severely. This will worsen food shortages and malnutrition. According to the United Nations, in some countries, yields from rain-fed agriculture could be reduced by up to 50 percent by 2020;
  • It is projected that crop yields could increase by up to 20 percent in East and South-East Asia while they could decrease by up to 30 percent in Central and South Asia by 2050. Overall, the risk of hunger is projected to remain very high in several developing countries; and
  • Illness and deaths due to diarrhoeal disease associated with floods and droughts are expected to rise in much of Asia as a result of global warming.

In addition to the polluter pays principle, another widely accepted fairness principle is that of ability to pay.

Capacity to pay principle says that nations or organisations that are wealthier should be required to do more than those that are poorer.

The ethical principle is similar to the idea of progressive taxation under which those who earn high incomes pay a higher rate of tax than those on low incomes. This is because an extra dollar of income means a lot more to a poor person.

Who will be more affected by climate change in Australia?

Within Australia, some groups of people will be more affected by climate change than others. For example:

  • In some regions, such as central Australia, the temperature will increase by more than the average;
  • Wealthier people will be in a better position to ‘weather-proof’ their homes than poorer people, including installing double-glazing and air-conditioning; and
  • Farmers may be more affected if climate change makes farming less viable economically, in areas such as the Murray Darling Basin.

Individual action versus collective action

Some people argue that we can solve climate change if everyone ‘does the right thing’. They say that governments are too slow to act and if we all pull together, we can sharply reduce Australia’s emissions.

Others argue that only collective action, through our governments, will work. They say that ‘privatising’ responsibility for climate change shifts the blame from governments and businesses onto the shoulders of individual consumers.

Greenhouse pollution is then attributed to our failure to ‘do the right thing’. While there are some things that individuals can act on, others are beyond the capacity of individuals alone.

When it comes to the food we eat or the clothes we wear, we can think about the greenhouse impact by finding out or demanding the information from the suppliers.

For example, meat and fish have a very high greenhouse impact in Australia.

When it comes to changing large systems over which we have no control, such as Australia’s energy systems, the most effective form of action is likely to be collective action.

For example, to vote for a council, state or national government that agrees to make the necessary changes and then to hold them accountable.

Fact: After several years of promoting ‘green power’ (renewable electricity) only 7 percent of Australian households have opted to pay more for electricity generated from renewable energy.

United Nations’ Principles

In 1992 the United Nation’s Rio Declaration and the United Nations Framework Convention on Climate Change established the ethical principles for climate change.




Everything we have said so far concerns the impacts of climate change on humans. If the well-being in human beings is all we care about, then our ethical position is called anthropocentric or human-centered.

But climate change will affect animals too.

The United Nations expects that approximately 20-30 percent of plant and animal species are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5-2.5°C.

In Australia, animals such as the mountain pygmy possum and the green turtle are expected to be at greater risk of extinction. In some areas, koalas will struggle to survive as eucalypts die off. Many species that depend on the Great Barrier Reef will also not survive.

If animals and plants have value in themselves, and not just because they promote human well-being, then they deserve to be protected too. So the extinction of species is an ethical issue.

Often we are not sure about the effects of our actions. We, therefore, have to make decisions in the face of uncertainty. In some cases, if we get it wrong we can change what we are doing and set things right.

For example, if a factory pollutes a river we may be able to clean up the contamination before it is too late. In other cases, if we get it wrong the effects may be irreversible.

For example, some types of contamination may kill an entire species of fish, and so the effect is that the type of fish is gone forever.

The extinction of a species is irreversible; once it’s gone, it’s gone forever. In these cases, we may apply what is known as the precautionary principle, which says that when we are uncertain about the likely outcomes, we should adopt a cautious approach and not take the risk.

It can also mean that if there is a risk that an action could lead to the extinction of a species, then those who want to take action should have to prove that it is safe.

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Module 4 – International Negotiations


If you have ever tried organising a group of friends to do something on the weekend and encountered great difficulties trying to reconcile one person’s preference for the movies with another’s preference for the beach, spare a thought for the 2,500 scientists who form the Intergovernmental Panel on Climate Change (IPCC).

It is their task to consider scientific research from dozens of nations and thousands of scientists around the world and channel it into one report that is agreed to by all.

The IPCC was established in 1989 by the United Nations and the World Meteorological Organisation. In 1990, it released its First Assessment Report that highlighted concerns about global warming and its environmental impact.

The report was extremely influential because, for the first time, thousands of scientists from around the world had reached a consensus on the existence of climate change and the likelihood that humans caused the problem.

In other words, the conclusions of the report had been agreed to by all the scientists involved, conclusions that could not be agreed to were not included.

The United Nations was founded in 1945 at the end of World War II in the hope that it would intervene in conflicts between nations to prevent future wars. Based in New York, it now has 192 members and numerous agencies that address a range of global issues including the environment.

In 2007 the IPCC and former US Vice-President Al Gore shared the Nobel Peace Prize for “their efforts to build up and disseminate greater knowledge about man-made climate change, and to lay the foundations for the measures that are needed to counteract such change”.


Since the release of its First Assessment Report, the IPCC’s Assessment Reports have grown in significance and influence.

Indeed two years after the first report, the United Nations-sponsored the Earth Summit in Rio de Janeiro where countries from all around the world signed onto the United Nations Framework Convention on Climate Change (UNFCCC).

This agreement set out the broad principles and objectives that kicked off the years of negotiations that created the Kyoto Protocol in 1997.


In 1997 representatives from countries around the world came together in Kyoto, Japan, to develop a plan to deal with global warming. The result was the Kyoto Protocol, a historic agreement that reflected over a hundred years of scientific research.

The Kyoto Protocol is a legally binding agreement made under the UNFCCC. It aims to avoid dangerous climate change. The first step was to set emission targets for developed nations to achieve between 2008 and 2012. It was always expected that later agreements would build on this, so the Kyoto Protocol was the first, not the last step.

Figure 1 Emission targets under the Kyoto Protocol, selected countries

As Figure 1 shows, each developed nation received individual emission targets, which were expressed as a percentage of their emissions in 1990.

Although three countries (including Australia) received a target that allowed emissions to increase from their 1990 levels, the combined effect of the Protocol, if all countries meet their targets, will be that average annual emissions will decrease by five percent below 1990 levels between 2008 and 2012.

Most of the countries that initially signed the Kyoto Protocol also ratified it. That is, they formally agreed to be bound by its obligations. Australia signed in 1998, but it did not ratify the Protocol until 2008.

By the start of 2008, 176 countries had ratified the Kyoto Protocol and the only developed country not to have ratified the Protocol is now the United States.

As far back as 1896, the Swedish chemist Svante Arrhenius claimed that increasing levels of carbon dioxide in the atmosphere could cause the planet to warm. He was the first person to warn that human activities could lead to changes in the Earth’s climate.


Although developed countries like the United Kingdom and Australia have been given emission targets, developing countries like China and India have not.

This may seem strange given that China is the second largest emitter of greenhouse gases after the United States. However, the decision is based on the principle of ‘common but differentiated responsibility’.

The first part of this principle recognises that while all countries share a common responsibility to reduce their emissions, historically it is developed countries that were the main contributors to the greenhouse gas emissions during the industrial revolution that is causing climate change today (see Module 5).

The second part of this principle recognises that rich industrialised countries are better able to introduce measures to reduce emissions than developing countries.

As a result, developed countries like Australia and the United Kingdom are to act first to reduce emissions, and developing countries will receive emission targets after that.


In December 2007, the newly elected Labor Government ratified the Kyoto Protocol, and as a result, Australia is legally bound to meet its target – see Figure 1.

For this to occur, Australia’s average annual emissions between 2008 and 2012 must be no higher than 567 Mt CO2-e, or 108 percent of the 1990 level.

The Government has stated that it is committed to meeting this target, but the most recent evidence indicates that Australia’s emissions will exceed the target level unless new policies are introduced quickly.

There has been controversy in Australia and internationally about Australia’s position towards Kyoto. Until December 2007, the previous Coalition Government, which had been in power since 1997, had refused to ratify the Protocol. Three main reasons were given for the decision.

  1. Kyoto is not in Australia’s economic interests.
  2. Developing countries like China and India are exempt from the Protocol.
  3. Australia will meet its Kyoto target anyway, so it does not need to ratify the Protocol.

The response from people who support ratifying the Protocol is as follows.

1. The costs from the Kyoto Protocol will be higher for countries that stay outside the Protocol because they will miss out on the economic benefits from carbon trading (this is explained in Module 8).

Environmentalists also point out that economic interests are not always the same as national interest especially when the likely impacts of climate change are taken into consideration.

2. Developing countries like China and India have ratified the Protocol, and the reason they do not have emission targets is that of the principle of common but differentiated responsibility (see above).

3. If Australia will meet the target, why not ratify the Protocol and gain the economic bene ts of participation?

Also, if Australia ratifies the Protocol, it will have a greater say in future negotiations that will have a big impact on Australia after 2012.


The attention of the international community is now turning to the agreement that will follow the Kyoto Protocol once it expired in 2012.

It is likely that the UNFCCC will continue to be the framework for reaching such an agreement, despite the past efforts of some countries (including Australia and the US) to set up different frameworks.

There is much more certainty about the science of climate change than there was in 1997 when the Protocol was signed, and greater urgency in finding solutions. Disturbingly, global greenhouse gas emissions are also much higher than they were in 1997.

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Module 3 – Australia’s Greenhouse Gas Emissions


In Australia, most of our greenhouse emissions come from the burning of fossil fuels (coal, oil and natural gas). Fossil fuels are used mainly to generate electricity and to power transportation.

Around 95 percent of our electricity comes from fossil fuels, and the only five percent comes from renewable energy. For transport, most Australians rely on cars, buses and ferries, which require another fossil fuel; oil, to run.

The clearing of land for agriculture, mainly for beef cattle grazing, also results in significant greenhouse gas emissions in Australia. When vegetation is cleared, some of it is burned immediately, releasing CO2 into the atmosphere.

Vegetation that is not burned together with the carbon in the soil eventually decays, releasing more CO2 for many years. Emissions are measured in millions of tonnes of carbon dioxide equivalent (Mt CO2-e).

In 1990 Australia’s emissions were 457 Mt CO2-e, but by 2005 they had risen to 559 Mt CO2-e, an increase of 22 percent. However, if land clearing is excluded, emissions rise by almost 26 percent – see Figure 1.

This is because land clearing rates have dropped in Australia since 1990. In the future, therefore, if Australia’s emissions are to be reduced the reductions must come from fossil fuel use.

According to Federal Government figures, between 1990 and 2003 land clearing declined by 367,000 hectares or almost 60 percent. This is equivalent to more than 500,000 football fields. Most of this reduction was in Queensland.

What is meant by carbon dioxide equivalent?

Other greenhouse gases – like methane (CH4) and nitrous oxide (N2O) – can be converted into their equivalent to carbon dioxide using factors that compare their global warming effect.

So one tonne of methane released into the atmosphere has the same warming effect as 21 tonnes of carbon dioxide. In this way, scientists can add up the effects of various greenhouse gases and measure them all regarding their carbon dioxide equivalent (CO2-e) (see Module 1).

Carbon dioxide, the main greenhouse gas, accounted for around 74 percent of all Australia’s emissions in 2005. The two other main greenhouse gases are methane, which accounted for 20 percent, and nitrous oxide, which accounted for 4 percent – see Figure 2.

 Figure 2 Contribution of main greenhouse gases, per cent, 2005

In 2005, the largest source of emissions in Australia was stationary energy that came mainly from electricity production (around 70 percent) but included direct emissions from manufacturing, metals and some other industries.

Stationary energy accounts for 50 percent of total emissions − see Figure 3. The other big contributors were transport (14 percent) and agriculture (16 percent).

Figure 3 Australia’s greenhouse gas emissions by sector, 2005


Sometimes people argue that because Australia only contributes 1.4 percent of global greenhouse gas emissions, any move to cut emissions in Australia would make no appreciable difference.

The most obvious way to compare Australia’s emissions is to look at the absolute number. In 2005 Australia’s emissions were 525 Mt CO2-e. In comparison, the UK had emissions of 657 Mt CO2-e, France 558 Mt CO2-e, and Italy 580 Mt CO2-e. This shows that if Australia’s emissions are too small to worry about, so too are those of the UK, France and Italy.

But there is another way to compare Australia’s emissions. We can look at how much each Australian is responsible for compared to people in other countries.

This involves taking the total amount of a country’s emissions and dividing it by the number of people in that country to determine the average emissions of each person.

 Figure 4 Greenhouse gas emissions per person in some industrialised countries, 2001

Figure 4 shows that Australia has the highest annual emissions per person of any industrialised country, around 27 tonnes per person. This is 30 percent higher than emissions per person in the United States (21.2 tonnes). In developing countries emissions per person are much lower – around three tonnes per person in China and one tonne in India.

There are three main reasons for Australia’s high emissions per person. First, electricity generation in Australia is very fossil fuel intensive, with coal being the main source (see Module 7).

Second, compared to many countries, Australia is not very efficient in its energy use. For example, fuel efficiency standards for cars in Australia are worse than those in China.

Finally, the mining, steel-making and aluminium smelting industries are large contributors to Australia’s total emissions. Because the Australian aluminium industry relies on coal-fired generation, the greenhouse gas emissions are around double the world average for each tonne of aluminium produced.

If wealthy nations like Australia, with high emissions per person, do not reduce their emissions it will be much more dif cult to encourage countries like China and India to reduce their emissions. (This is discussed further in Module 5 on ethics and climate change).

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Module 2 – The Impacts of Climate Change

The impacts of climate change are already being felt. The emission of greenhouse gases by human activities is resulting in increased surface temperatures that are causing multiple and complex changes to the climate at both a global and regional scale.

When we think about climate change, there are two important points to remember. Firstly, climate change affects both natural and human systems.

The impacts that are felt will not only depend on how large and rapid the change may be but also on how vulnerable or adaptable the system is.

Secondly, predictions of warming are based on climate models, which can vary significantly. Global precipitation (rainfall and snow) for example, is expected to increase by between 1 and 9 percent by 2100.

Such differences make it more difficult to predict how serious and/or possible long-lasting impacts may be, and how large an area will be affected.


In 2007 the Intergovernmental Panel on Climate Change (IPCC), described in Module 4, released its latest report on climate change. It found that:

  • In the last 100 years the earth has warmed by 0.74°C;
  • Eleven of the past 12 years (1995-2006) rank among the twelve warmest years since 1850; and
  • There is a risk that by the end of the 21st Century temperatures could rise by between 1.1 and 6.4°C.

Climate models tend to show that the greatest warming will occur over inland areas of continents and in the northern hemisphere (because of the greater proportion of land mass).

By contrast, less warming will occur over oceans and coastal zones. The least warming will occur over the Southern Ocean because of its large capacity to transport surface heat into deeper waters.

It is also expected that warmer conditions will occur along the coast of South America, so that El Nino conditions (which is associated with drought in Australia) may become more common. Because the Earth’s climate system is so complex, warming could continue for centuries, even after greenhouse gas concentrations are stabilised.

Increased global temperatures are already associated with a reduction in polar ice, melting of glaciers and thawing of permanently frozen ground in high latitudes (such as the Russian tundra).

At a regional or local scale, it is uncertain as to how much climate change will affect snowfall and the altitude of snowlines, which could likely affect winter sports like skiing.

Australian data indicates that the length of the snow season and the volume of snow is decreasing over time. On the other hand, warmer air can hold more moisture, so it is possible that in humid areas (such as the South Island of New Zealand), warming could be associated with increased snowfall.

Substances called gas hydrates (ice-like solids in which gas molecules are trapped) are locked up in water within the frozen ground. It is estimated that gas hydrates contain twice the total volume of carbon in existing coal, oil and gas deposits on Earth.

Thawing of frozen ground due to global warming may destabilise these substances, which would release large volumes of methane back into the atmosphere, further enhancing the greenhouse effect.


The increase in ocean temperatures will not only melt polar ice and glaciers, but it will also make the volume of water in oceans expand. Both of these processes contribute to rising sea levels.

As waters rise, there is a greater risk of the edges of ice shelves and coastal glaciers collapsing into the sea, thereby causing further sea level rise.

Due to historically favourable climatic conditions, coastal zones throughout the world are densely populated. In Australia, 84 percent of the population lives on the coast.

Rising sea levels will place some of these people at risk, due not only to waterlogging and submergence of land but also to damage by wave action and storm surges.

The environments most vulnerable to sea level rise are low-lying oceanic islands, particularly island atolls, and river deltas, such as the Ganges delta in Bangladesh.

In these localities, rising sea levels are already causing groundwater levels to rise, and submergence during high tides are becoming more frequent.

Concerns are now emerging that many island atolls will become uninhabitable, forcing migration of human populations and extinctions of island fauna and flora.


Changes in global temperatures will also lead to more frequent extreme climate events. It is anticipated that the number of sweltering days will increase with fewer colder and frosty days.

Also, intense summer heat could result in more violent storms, and tropical cyclones as the oceans warm and more energy are stored in our warming atmosphere. This could cause greater flooding, mud/landslides, and damage to buildings, roads and bridges.

By contrast, in the mid-latitudes, particularly in inland regions, more frequent and prolonged drought could be associated with reduced water supply, lost productivity and possibly famine. Also, drier conditions will cause more frequent and higher intensity bush res.

A Case Study: Bushfires


Each December, as Australians begin their summer holidays, their television screens invariably begin to show pictures of bush res threatening lives and property.

In January and February, it is not uncommon to hear reports of firefighters attempting to control many fires as resources criss-cross the country to assist those most in need.

The most recent and devastating of these episodes was 2002-03 preseason. Over three million hectares of bushland and vegetation were destroyed across the country. In Canberra, the worst affected city, four people died, 501 houses were lost, and over 160,000 hectares were burnt.

Recent projections indicate that climate change could raise the risk of fire in Australia. According to the CSIRO, climate change will increase the frequency of very high and extreme fire danger days by 4-25 percent by 2020 and 15-70 percent by 2050 across south-east Australia.


In Australia, the increased incidence of drought and reduced runoff will affect water supply to farmers, irrigators and cities. In a drying environment, water use by crops will increase, creating a greater demand for irrigation water.

However, there will be less runoff filling storage dams so it will become increasingly difficult to meet those demands.

Under these conditions, water will become an increasingly precious resource. The water of high quality will be particularly valuable since a decrease in the amount of water flowing through rivers and streams will affect the water quality. For example, the salt content (salinity) could increase.


Ecosystems throughout the world are already experiencing unprecedented pressures from human activities that make them increasingly vulnerable and less capable of adapting to ongoing changes, including climate change.

In the next hundred years ecosystems will be exposed to the highest CO2 concentrations or 650,000 years, and the highest global temperatures in 740,000 years. These conditions will reduce biodiversity (the number of plant and animal species present), and the function of most ecosystems.

An ecosystem is a complex community of animals, plants and micro-organisms which interact with the non-living environment (such as soil, rock and water). Ecosystems are essential to human well-being and overall environmental health.

About 20-30 percent of plant and animal species will be at risk of extinction if global temperatures rise 2-3oC above pre-industrial levels. In marine environments, sea water will be warmer and carry more dissolved CO2 (making it more acidic) and hence more difficult for some species to live.


Human health, safety and living standards will be increasingly affected by climate change. There are likely to be more instances of heat-wave induced illness and death such as the 2003 summer heatwave in Europe that killed an estimated 35,000 people.

Conversely, in the Northern Hemisphere, there may be fewer deaths related to cold weather. Loss of life, injury and loss of infrastructure from natural disasters such as fire, flood, drought, landslides and storms could increase as well.

Secondly, sea level rise will be associated with increased risks of inundation, storm surges and the failure of sanitation systems. This can lead to loss of productive land, and associated food shortages, an increase in disease, and loss of fish nurseries (also an important food source).

Indirect, longer-term impacts include a change in the incidence and distribution of infectious diseases, especially those that are transmitted through animals and insects that carry human disease.

These include malaria, dengue fever and rabies. Where drier conditions develop, a higher incidence of respiratory disease associated with pollen and dust can be anticipated.

A word of caution relating to human health issues: while these impacts have been identified, there is little hard evidence to date of the effects of observed climate change on health.

Impacts of climate change on ecosystems

As Figure 1 shows, the projected impacts of climate change are many and could be expressed either as rapid shifts or slow, progressive changes. Some of the changes may be manageable, particularly if greenhouse gas emissions stabilise, but others will be irreversible.

The great barrier Reef is a world heritage site located off the coast of Queensland. Home to a network of some 2,900 reefs, thousands of species and seagrass meadows, it is now under threat from climate change.

For example, higher temperatures, and the number of scorching days (above 35oC) create the risk of coral bleaching leading to coral death.

Besides, more severe tropical storms could physically damage sections of the reef. Any destruction of the reef is also likely to affect the thousands of people employed in tourism in and around the reef.

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Module 1 – The Science of Climate Change


Have you ever wondered why it could rain one minute and be sunny the next, but why it is always drier in central Australia than it is on the coast?

The reason is simple: while the weather can change quickly, with big variations over a day, the climate changes over much longer timeframes. Rainfall patterns do not simply change overnight.

Changes in the weather are well-understood and despite what many people think meteorologists are pretty good at predicting what the weather will be the following day.

The climate is a different matter. The Earth’s climate system is affected by the interactions of different subsystems such as the atmosphere, the hydrosphere (the oceans and rivers) and the biosphere (including the forests, the plants and the soil).

Although individual interactions between, for example, the forests and the atmosphere are well understood, the way all these different subsystems interact is very complex and much harder to understand.

In the past, scientists have had great difficulty understanding and predicting changes in the climate. More recently, reliable evidence has emerged of how these subsystems have interacted to produce past climatic changes.

Using complex climate models that have been improved with sophisticated computer programs, scientists have been able to simulate the weather and the climate and to predict the changes that could follow from human-induced changes that may occur.

A model is a set of mathematical equations that represent interactions between various components of a complex system. Models can never capture all of the complexity of a system like a climate or the economy, so there is always some uncertainty remaining.

Climate models simulate the interactions between the different subsystems. For example, they can predict, to a degree, the impact on the climate if huge tracts of the Earth’s forests are destroyed.


The Earth’s atmosphere is like a big blanket that surrounds the globe keeping humans warm. If it were suddenly stripped of the Earth’s average temperature would plummet, and everything would freeze.

Like a blanket that could be made from a mix of cotton and wool, the Earth’s atmosphere is made from a mixture of gases. The main gases are nitrogen, oxygen and argon. However, there also trace gases such as carbon dioxide, water vapour, methane, ozone and nitrous oxide. These are called the greenhouse gases because they create a warm environment for the Earth.

The greenhouse effect occurs because the Sun’s shortwave radiation passes through the atmosphere and warms the Earth’s surface. This warm surface then radiates long wave infra-red radiation back into space. However, the greenhouse gases absorb some of the infrared radiation and re-radiated back to the atmosphere and the ground.

This makes the temperature of the atmosphere and the Earth higher than it would be without the presence of the greenhouse gases – see Figure 1.

Figure 1 - The Greenhouse Effect

The process is similar to how a greenhouse traps warmth and why the term greenhouse effect has become part of everyday language. Any change to the volume of greenhouse gases, therefore, changes the temperature on Earth. It is a bit like putting an extra blanket on your bed – it traps more of your body heat under the covers. As the earth slowly warms, the whole climate system is affected.

Some greenhouse gases such as carbon dioxide are constantly added to and removed from the atmosphere by natural processes. However, the recent increase in their concentration and the addition of new gases due to human actions is the driving force of changes in climate that the world is now experiencing.


Since the middle of the 19th century and the Industrial Revolution, when major changes occurred in agriculture, manufacturing and transportation:

  • Including the replacement of organic fuels like wood with fossil fuels like coal
  • The concentration of greenhouse gases (except water vapour) has been increasing.

For example, the concentration of carbon dioxide (CO2) in the atmosphere has been increasing rapidly since the Industrial Revolution as we have burnt more fossil fuels – see Table 1.

To check whether this might simply be a coincidence, scientists have examined the long-term geological record to see whether the increase in CO2 over the last two centuries is normal or unusual.

Ice cores were taken from Antarctica, and the Arctic indicate that, since pre-industrial times, the concentrations of CO2 have risen at a rate that has no precedent in the geological record.

There are no known natural processes that would create such a large increase in CO2, so scientists conclude that human activities are the main cause of the increase in CO in the atmosphere.

In addition to burning fossil fuels, clearing of forests and the release of industrial gases such as refrigerants have also contributed to the enhanced greenhouse effect.

Another of the main greenhouse gases is methane (CH4), which is 25 times as effective a greenhouse gas as CO2 on mass for mass basis.

This means that although methane is less abundant than CO2, its presence has a major impact on heat absorption in the atmosphere.

In other words, although most of the blanket surrounding the Earth is made of CO2, the part made of methane is a bit like pure wool, it keeps you very warm.

Methane is generated by the bacterial decay of dead plant and animal material (including in waste landfills), by livestock farming (due to fermentation processes in the gut of ruminants such as cattle), rice cultivation, and by leakage from fossil fuel production processes such as coal mining and natural gas distribution.

The analysis of ice cores indicates that changes in methane concentrations in the atmosphere over time coincide with rises in the human population.

This suggests that human activities associated with urbanisation, industry and agriculture are all significant factors in methane production, and hence climate change.

In addition to these two major greenhouse gases, other trace gases that are important include nitrous oxide (N2O), ozone (O3) and water vapour, as well as a range of synthetic gases with chlorine or fluorine in their molecular structures.

These are known as chlorofluorocarbons (CFCs). Similar patterns of change since the industrial revolution are also evident with these gases, which can be attributed to various human activities.

The issue of ozone depletion is an entirely different process to the greenhouse effect. The two are commonly confused, but they are, simply, two destructive processes occurring in the atmosphere in response to human activities.

The Ozone Layer

Ultraviolet radiation is a part of the solar radiation spectrum. It causes sunburn and is deadly to living organisms, including humans. Ozone can absorb the most lethal type of ultraviolet rays and is therefore crucial to life on Earth.

Since 1980, the ozone in the atmosphere has been depleted by around four percent per decade largely because of pollutants emitted from human manufactures, such as chlorofluorocarbons (CFCs).

Although the two are commonly confused, ozone depletion is different from the enhanced greenhouse effect. While some materials with a greenhouse impact also affect the ozone layer (for example, CFCs), they are two quite distinct environmental problems that affect the atmosphere.


Climate is unpredictable and changes over time. This is called ‘natural variability’ and is caused by:

  • The complex, chaotic behaviour of the many subsystems like the atmosphere and the oceans that make up the climate;
  • The natural oscillation, or swinging, between warm and cool periods over years, decades or centuries, such as the El Nino effect;
  • Variations in solar activity such as sunspots; and
  • Random volcanic eruptions, which can put soot into the atmosphere and cause cooling.

The study of ice cores, coral and tree rings have helped scientists understand how the climate has varied over the past. This has been helped by the use of climate models.

By understanding natural climate variability, we can use the models to compare trends in climate in the post-industrial period with past climates.

Scientists have discovered that the rate of global warming and climate change is far beyond what can be explained by natural variability.

Based on the work of around 2,500 scientists, the United Nations Intergovernmental Panel on Climate Change (IPCC, see Module 4) has concluded that there is a 90 percent certainty that humans are the cause of climate change.


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