Introduction to Climate Change
This page provides background information on the science and politics of climate change, in the following areas:
In simple terms, climate can be defined as the “average weather”. The period of time used by scientists to establish the average is typically at least 30 years. So, climate change can be viewed as any change in the average weather over an extended period of time. (This means that scientists do not draw conclusions from single events, such as the retreat of a single glacier, or a particularly hot year. Rather, they collect evidence over larger spatial and temporal scales.)
Climate changes have occurred throughout the Earth’s history (over 4 billion years). Various factors are known to influence the climate, including:
- The emission of energy from the Sun (e.g. sun spots)
- The distance between the Earth and the Sun
- The shape of the orbit of the Earth around the Sun
- The shape and position of ocean basins and continental crustal slabs
- The abundance of carbon dioxide and other greenhouse gases in the atmosphere (the greenhouse effect)
However, these days climate change is more commonly associated with the effect of human activities on the climate through an enhanced greenhouse effect. The United Nations’ climate change body (UNFCCC) defines climate change as “a change in climate which is attributed…..to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability…..”.
The main international scientific body investigating climate change is the IPCC (The International Panel on Climate Change). (See below for some background on the IPCC.)
In 2007 the IPCC concluded the “warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level”.
The IPCC reported an average global temperature increase of 0.74º between 1906 and 2005, with most of that rise occurring in the last 50 years. Whilst this might not seem significant, in climatic terms it is exceptional.
There are many other indicators of climate change, including the thawing of the permafrost, later freezing and earlier break-up of ice on rivers and lakes, and poleward and altitudinal shifts of plant and animal ranges.
The consensus amongst the global scientific community is that the increase in average global temperatures is primarily a result of increases in greenhouse gas (GHG) concentrations in the atmosphere. The main GHG is carbon dioxide (CO2), but there are also significant contributions from methane, nitrous oxide and various industrial gases.
Such increases are explained by human activity, primarily the burning of fossil fuels (e.g. burning coal for electricity and petrol for transportation), but also from land use changes (especially deforestation and agriculture).
The IPCC concluded that “most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic (human) GHG concentrations.” The IPCC models suggest that without the increase in GHG emissions then the natural effects from the Sun and volcanic activity would have produced a cooling effect. This last point is important, as some people (the so called deniers or sceptics) argue that the observed changes are due to natural phenomena.
Global GHG emissions due to human activities have grown since pre-industrial times, with an increase of 70% between 1970 and 2004. Atmospheric concentrations of CO2 have risen by over a third since the start of the industrial revolution (from 280ppm to 390ppm).
One key point is that most GHGs stay in the atmosphere for a long time; for example on average a CO2 molecule stays in the atmosphere for about 100 years. So even if there is a reduction in the release of GHGs, it will be many years before the greenhouse effect begins to return to a natural level.
There are predicted to be a variety of ways in which humans will be affected. Expected impacts include changes in water availability, crop productivity, coastal erosion, coastal flooding, and impacts on health.
These effects will vary across the different regions of the world. Whilst there are likely to be some direct positive effects in some areas of the world, overall the effects are expected to be negative. In general, less developed areas of the world (e.g. Africa, parts of Asia) are expected to be more affected as they have less ability to adapt (i.e. they are poorer). The severity of the effects is then likely to result in destabilization of these societies.
This destabilization can then be expected to affect the other regions (generally the developed countries, which are less directly affected by climate change), through disruption to global human systems and mass migrations of people from the affected areas.
The IPCC and mainstream scientific opinion think that there will be severe impacts on the Earth’s climate and ecosystems, and therefore on humans, if temperatures rise more than 2°C above pre-industrial levels by the end of this century.
There has already been a 0.6°C rise and GHGs already released will add a further 0.5°C rise (through the persistence of GHGs in the atmosphere).
The extent of the impacts on human society over the next century, and beyond, depends on the actions that are taken over the next few decades.
In general there are two types of action - mitigation and adaptation. In effect, mitigation is about dealing with the cause, and adaptation is about coping with the effects.
Mitigation involves trying to reduce the levels of GHGs in the atmosphere, both by reducing the release of more GHGs into the atmosphere (e.g. reduction in fossil fuel burning) and by taking CO2 from the atmosphere (e.g. by planting more trees). Effective mitigation will only be possible through carbon pricing; policies which promote clean technology development; and policies which encourage greater energy efficiency.
Adaptation involves establishing ways to cope with the various effects of climate change, primarily through the use of technology.
It is generally accepted that there is an urgent need for very significant mitigation action, in order to initially slow and stop the rise in GHG emissions, and then reduce them. There will still be a need for adaptation action, but the scale of action needed will be less if earlier mitigation action is effective. (Key studies, such as the UK Government’s Stern Report, have concluded that mitigation action is much more economic.)
There is a general consensus that GHG emissions reductions of between 60% and 80% (from 1990 levels) are needed to keep the global temperature increase less than 2º. This corresponds to a CO2 stabilisation at between 450-550ppm.
This means that GHG emissions need to peak within the next decade, and then begin a steady reduction over the following few decades.
Following on from the early work of the IPCC, and the worrying conclusions reached, an international treaty (the Framework Convention on Climate Change) was agreed by United Nations members in 1992.
The treaty included several basic principles, including that:
- Remaining scientific uncertainties should not be used as a reason for inaction;
- Action should aim to stabilize atmospheric GHG concentrations at safe levels, so that ecosystems could adapt, food production would not be threatened, and to enable economic development to continue in a sustainable manner;
- Action should be based on ‘common but differentiated responsibilities’ between countries, with the developed countries taking the lead by aiming to ‘return their emissions to former levels’.
The Kyoto Protocol treaty was negotiated in 1997 with developed countries having specific, legally binding, emissions targets. The country specific targets were set relative to 1990 levels, with the overall effect of the treaty being to reduce the emissions of the participating countries to 1990 levels.
However it took until 2005 until the treaty came into force, once a threshold number of countries had ratified the treaty (i.e. passed it into law by their parliaments). However, most significantly the USA did not, and has not, ratified the treaty.
There has been a mixed level of progress amongst the ratification countries. Whilst some countries have taken important steps, including those in the European Union (with the introduction of carbon pricing through the EU Emissions Trading Scheme), most countries are not expected to reach their target reduction by the end of the treaty period (2012). So, the Kyoto Protocol has not been a great success so far. This can be explained by several key reasons:
- The lack of involvement of the developed country with the highest emissions (USA) and the consequent loss of the country most capable of providing international leadership;
- The exclusion of the major developing countries (e.g. China, India) from the treaty and the consequent limitation in the ability of the developed countries to implement meaningful change without affecting competitiveness; and
- The scale of the challenge, in terms of the infrastructural and societal changes required to begin to reduce emissions.
The Copenhagen conference in December 2009 was expected, or at least hoped, to be the event where significant progress was made on agreeing the next stage of international action on climate change, following the end of the Kyoto Protocol in 2012.
Despite the presence of most world leaders, including US President Barack Obama and the prime ministers of China and India, the conference failed to live up to these hopes and expectations, with no binding agreement produced.
The only output was the Copenhagen Accord. The main points of the accord are:
- The accord is not a legally binding agreement, unlike the Kyoto Protocol. It is more a statement of intent.
- However it does, unlike any previous agreement, state that action should be taken to try and limit the temperature increase to 2 degrees Celsius.
- There is a commitment from the developed world to provide finance to the developing world to help with mitigating, and adapting to, climate change, including providing US$100 billion a year by 2020.
- Developed countries (Annex I Parties) are required to set emissions reduction targets for 2020, and report on progress towards those targets in line with existing practices.
- For the first time, there is a requirement of developing countries (Non-Annex I Parties). They must define and implement mitigation actions which they will take to limit their emissions, and report on the outcome of these actions. But, there is no need for independent verification.
- There is a stated recognition of the crucial need to reduce deforestation and enhance reforestation in developing countries, through financial incentives provided by developed countries.
How the world responds in 2010, leading up to, and at, the next conference in Mexico later this year, will be critical. Failure to build on the accord and reach a binding agreement, which involves all leading emitting countries, on a successor to the Kyoto Protocol, will make prospects for meaningful action seem bleak.
The IPCC (The International Panel on Climate Change) is the scientific intergovernmental body that has undertaken the most comprehensive scientific analyses and impact assessments on climate change matters.
The IPCC was set up by the World Meteorological Organisation (WMO) and the United Nations in 1988, with the support of all leading countries (including the US). Its mandate is to provide the decision-makers and others interested in climate change with an objective source of information about climate change. Hundreds of scientists from all over the world contribute to the work of the IPCC as authors, contributors and reviewers.
The IPCC does not conduct any research nor does it monitor climate related data or parameters. Its role is to assess, on a comprehensive, objective, open and transparent basis, the latest scientific, technical and socio-economic literature produced worldwide relevant to the understanding of the risk of human-induced climate change, its observed and projected impacts and options for adaptation and mitigation.
To date, the IPCC has issued 4 assessment reports, each looking at the three main aspects of climate change: the physical science, the likely impacts, and the options for mitigation.
Each report has concluded, with progressively higher levels of certainty, that human-induced climate change is a reality, and that the effects will be severe if no action is taken. The latest report, issued in 2007, whilst noting that some areas of uncertainty exist, stated an overall very high level of certainty (90%).
The IPCC uses six scenarios to determine the likely extent and impact of climate change. Each scenario is based on different approaches to mitigation, from a business-as-usual approach (where no attempt is made to reduce GHG levels) to one which rapidly implements clean technologies through high levels of global cooperation.
The findings of the IPCC have been endorsed by most leading scientific bodies (such as UK’s Royal Academy and the USA’s National Academy of Sciences).
New Zealand GHG emissions have grown by over 40% since 1990 (the Kyoto Protocol base year). Whilst the country produces only 0.4% of global emissions, it ranks very high in terms of relative emissions; amongst OECD countries, it is the 4th highest for emissions per unit GDP and 5th highest for emissions per capita).
New Zealand has an unusual emissions profile, with agricultural emissions (methane and nitrous oxide) accounting for nearly half the emissions, with transport and other energy use accounting for most of the remainder. The country has relatively low energy (non-transport) impact due to the hydro contribution to electricity, but recent years have shown a rise in fossil fuel contribution to electricity production. (Most of the increase in demand over the last few decades has been met by increases in non-renewable sources, e.g. gas and coal.)
New Zealand will not be immune from the impacts of climate change.
In their 2007 report, the IPCC concluded that rainfall will reduce in Northland and in some eastern regions, leading to water shortage risk. They also noted that some coastal areas from Northland to the Bay of Plenty were at risk from sea-level rise and increases in the severity of storms and coastal flooding by 2050. However, at least initially, there may be benefits in western and southern areas due to a longer growing season, less frost and increased rainfall.
The IPCC concluded that although New Zealand has good adaptive capacity (i.e. the ability to cope with the changed conditions), there will still be major challenges from extreme events.
In addition, the country will not be immune from the effects of disruption in other areas of the world, which may result in disruption to the established world systems (including trade), and pressure on borders (from migration of peoples from severely affected areas.)
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Royal Society of New Zealand statement on climate change available here.