Climate change

What is climate change mitigation?

Climate change refers to any change in climate over time, whether due to natural variability or as a result of human activity. The science supporting climate change mitigation seeks to understand these changes and their drivers to improve the knowledge underpinning mitigation policy.

Climate change mitigation includes actions we take globally, nationally and individually to limit changes caused in the global climate by human activities. Mitigation activities are designed to reduce greenhouse emissions and/or increase the amounts of greenhouse gases removed from the atmosphere by greenhouse sinks.

Global goal for mitigation

‘During the past million years, the average temperature of the Earth’s surface has risen and fallen by about 5°C, through 10 major ice age cycles. The last 8,000 years, however, have been relatively stable at the warmer end of this temperature range’ (Australian Academy of Science 2010).

Human civilisations have flourished in this relatively stable climate. We depend on water supplies that rely on a certain type of climate, and our agriculture depends on certain patterns of rainfall and temperature. A shift in these stable weather patterns will affect all aspects of our lives, including our capacity to grow food, the availability of water, where we live, the infectious diseases and pests that thrive in our region and affect our health, and our ability to keep our homes and families safe from extreme weather.

‘Dangerous’ climate change

The goal for global mitigation was set in 1992 by the (United Nations Framework Convention on Climate Change-UNFCCC) as: ‘stabilisation of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system’ (Article 2, UNFCCC).

Although the UNFCCC mentions ‘dangerous anthropogenic interference’, it does not define it. In 2009, a formal definition for ‘dangerous’ climate change was adopted as part of the Copenhagen Accord. Under this agreement, global efforts would focus on limiting the rise in global average temperatures to 2°C above pre-industrial levels.

Our understanding of climate sensitivity (see Our climate system: how it works and changes) and the consequences of global warming (see Climate change impacts in NSW) continues to improve. In 2010 governments agreed to review the level of agreed global warming and consider whether it should be limited further to 1.5°C above pre-industrial levels (Cancun Agreement).

Uncertainties in projections

Although a precise value for the likely warming cannot be calculated because of uncertainties about how the climate system will respond to small disturbances and to mitigation activities, climate models and evidence from past climate change are able to provide a plausible range of values.

The international scientific community is working hard to understand and narrow down the uncertainties in future climate projections, through modelling, observations and synthesis of results.

It is possible that there will be rapid transitions in the climate or ‘tipping points’ associated with global warming, but they ‘… cannot yet be predicted with confidence. These uncertainties work in both directions: There is a chance that climate change will be less severe than the current estimates of climate science, but there is also a chance that it will be more severe’ (Australian Academy of Science 2010).

Effect of greenhouse gas levels on global temperatures

Two different approaches—climate system modelling and studying past climates—both tell us that global warming will continue as the concentration of greenhouse gases increases in the atmosphere. Both methods project a warming of around 3°C (within a range of 2°C to 4.5°C due to uncertainty) in response to a doubling of the concentration of carbon dioxide in the atmosphere.

'Continued “business as usual” reliance on fossil fuels is expected to lead to a doubling of pre-industrial levels of carbon dioxide by about 2050, and possibly a tripling by about 2100. This emission pathway for carbon dioxide, coupled with rises in the other greenhouse gases, would be expected to produce a warming of around 4.5°C by 2100, but possibly as low as 3°C or as high as 7°C’ (Australian Academy of Science 2010).

Research into mitigation

Climate change mitigation actions are designed to reduce greenhouse emissions and increase the amounts of greenhouse gases removed from the atmosphere by greenhouse ‘sinks’. The oceans, plants and soils are carbon dioxide sinks because they absorb more carbon than they emit (for more information, see Causes of climate change).

Globally, scientific and technological research is under way into how to reduce the amount of greenhouse gases that we emit. This includes research into:

  • cleaner energy supplies such as electricity from renewable sources and automotive biofuels
  • using energy more efficiently to avoid burning fossil fuels
  • developing more efficient transport
  • improved cropland and livestock management
  • better waste management
  • reducing land clearing and deforestation.

As carbon dioxide accumulates in the atmosphere, natural sinks of carbon dioxide become even more important as a means of absorbing additional concentrations.

More information