Annex 4: Global warming and climate change

The effects of climate change
Evidence for climate change
What are the greenhouse gases?
The international response to climate change

The temperature of Earth’s surface has risen over the past 100 years. A small part of this increase has probably been caused by natural climate variations but there is strong evidence that most of the warming over the past 50 years is a result of greenhouse gas emissions caused by human activity.

Greenhouse gases got their name because they act like the outside covering of a greenhouse, letting the sun’s warmth through to heat the ground, but preventing it from escaping back into space. Greenhouse gases absorb heat radiated or reflected from the ground, increasing the temperature of the atmosphere. Greenhouse gases that naturally occur in the atmosphere make life on earth possible. Without them, too much heat would escape, and the surface of the planet would freeze. However, in too high a concentration, they would hold in excessive heat and the planet’s climate would become more and more unstable.

Climate models predict that greenhouse gas emissions will continue to increase atmospheric temperatures. The rise projected for the next 100 years is likely to be more rapid than any natural variations over the past 10,000 years. Because rising temperatures cause changes (often drastic) in the climate, the effect of global warming is often referred to by the more general term, ‘climate change’.

The effects of climate change

The effects of climate change are already measurable – the world’s temperatures and sea levels are rising, and most glaciers are retreating. Changes in regional rainfall patterns have already been observed and are expected to alter more strongly as climate change continues. The frequency of some extreme weather and climate events such as heatwaves, droughts and floods is also expected to increase. These changes are likely to influence native ecosystems, agriculture, coastlines, and our economy, infrastructure, health and security. For example, changing weather patterns could cause increases in the number of refugees seeking international support, as repeated droughts and floods drive people from their traditional homes.

Not all impacts will necessarily be negative and the severity of impacts will vary across the globe. But it is almost certain that, overall, more people will be harmed by climate change than will benefit from the changes. Adverse impacts will become ever more predominant, and beneficial effects are expected to diminish because of larger cumulative emissions of greenhouse gases and associated changes in Earth’s climate. Because of the long life-time of some greenhouse gases in the atmosphere, there will be time lags of decades to centuries between reductions in emissions and a corresponding halt to temperature increases.

As temperatures rise, insects and organisms that are not usually found in New Zealand because they prefer warmer climates, could become established.

Evidence for climate change

There is now clear evidence that Earth’s climate system has demonstrably changed since pre-industrial time, and that most of the warming over the last 50 years has been caused by emissions of greenhouse gases created by humans. The Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) reports that warming is expected to continue, with an increase in globally averaged temperatures of between 1.4 and 5.8° C.

This is two to ten times larger than observed warming in the 20^th century. How high the temperatures go, how soon, and whether changes can be reversed, depend on human action. The greater the reduction in greenhouse gas emissions, and the earlier they are made, the smaller and slower the projected warming and rise in sea levels.

What are the greenhouse gases?

The main greenhouse gases are:

Methane from farm animals and waste
Nitrous oxide from soil
Synthetic gases like sulphur hexafluoride, perfluorocarbons and hydrofluorocarbons.

Carbon dioxide from burning of fossil fuels and from deforestation

The international response to climate change

The international community has recognised that the issue of climate change needs a global response and that it is sensible to start limiting the growth of greenhouse gas emissions now in order to reduce the negative impacts expected from future global warming. Countries have been working through the United Nations to achieve this.

Two important international agreements deal with the threat of global climate change. The United Nations Framework Convention on Climate Change (UNFCCC) was adopted at the Rio Earth Summit in 1992. The Kyoto Protocol, a further agreement negotiated in accordance with the UNFCCC, was finalised in December 1997.

The objective of the UNFCCC is to stabilise greenhouse gas concentrations at a level that avoids dangerous human interference with the climate system. As mentioned earlier, New Zealand is one of 180 countries that signed and ratified the UNFCCC. All developed countries that ratified the UNFCCC agreed to non-binding targets to reduce greenhouse gas emissions to 1990 levels by 2000. Only a few countries made appreciable progress towards achieving those targets.

The UNFCCC was designed so that it could be developed further by countries in response to new scientific evidence that suggested the objectives of the UNFCCC would not be met by voluntary reductions and that legally binding targets were required. They agreed to a further international agreement, the Kyoto Protocol.

The Protocol sets target levels of greenhouse gases for developed countries to achieve during 2008-2012 (the first Kyoto Commitment Period). The Protocol is only the first step in the reduction of greenhouse gases worldwide, and it is expected that further, stricter targets will be set in future commitment periods. New Zealand signed the Protocol in 1998, and has been actively involved negotiating the detailed rules by which it will operate.

To enter into force, the Protocol had to be ratified by at least 55 parties to the UNFCCC, including countries representing at least 55 percent of the developed world’s emissions. This happened on 16 February 2005. International negotiations are now underway to agree the framework to address climate change at the end of the first Kyoto Commitment Period.

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