Certain gases in the atmosphere (commonly referred to as greenhouse gases) block the heat being reflected back to space and radiate it back to the Earth's surface, having an insulation effect. Water vapour is the main natural greenhouse gas. Other gases include carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6).

While water vapour is the most significant natural greenhouse gas, it cannot be controlled by humans. Human activity has, however, influenced the atmospheric concentrations of the other greenhouse gases listed above. Since the beginning of the industrial revolution (about 1700 A.D.), the levels of other greenhouse gases in the atmosphere have significantly increased. This increase is largely associated with human activities such as the combustion of fossil fuels and vegetation changes. As a result, more radiation is being trapped in the Earth's atmosphere, causing it to warm (global warming).

Climate change is a global environmental problem, predominantly caused by human activities. The likely effects of climate change include rising average temperatures, rising sea levels, more frequent extreme weather events and a change in rainfall patterns. There is strong scientific consensus that, by the end of this century, these changes will occur on a scale that will cause serious harm to ecosystems, industries, infrastructure, human health, biosecurity and economies world wide.

This global warming has begun to affect the world's climate. The effects on weather patterns and larger scale climatic trends are expected to become steadily more pronounced over time.

There will be both positive and negative consequences of climate change. But globally, more people are likely to be harmed by the effects of climate change than will benefit. If greenhouse gas emissions are not reduced significantly over the coming decades, the impacts of climate change will more than likely get steadily worse and the costs could be severe.

In response to this risk, the Kyoto Protocol was initiated to try to reduce global greenhouse gas emissions, with each member country being set reduction targets. Under the Kyoto Protocol, New Zealand will have to limit net average greenhouse gas emissions to 1990 levels during the period 2008 to 2012 (the first commitment period).

Almost 62 million tonnes of CO2 equivalent were emitted in 1990, meaning that New Zealand must take responsibility for any emissions in excess of its 307 million tonnes allocation over the first commitment period. New Zealand is steadily increasing its greenhouse gas emissions. Current estimates suggest total emissions for 2002 were 22% higher than in 1990 (excluding net removals from forest sinks).

In order for New Zealand to meet its Kyoto Protocol target the Government has introduced a climate change policy. This policy includes the use of an emissions charge, incentives for greenhouse gas emission reduction projects, agriculture sector funded research, negotiated greenhouse agreements (NGAs) with mainly larger industries, the encouragement of forest sinks and the possible use of emissions trading.

For this policy to be a success the Government requires the assistance and cooperation of a wide variety of sectors of the economy.

Further information in relation to this policy can be found at the New Zealand Climate Change Office website www.climatechange.govt.nz.