Carbon credit: a generic term to assign a value to a reduction or offset of greenhouse gas emissions.  A carbon credit is usually equivalent to one tonne of carbon dioxide equivalent (CO2-e).  A carbon credit can be used by a business or individual to reduce their carbon footprint by investing in an activity that has reduced or sequestered greenhouse gases at another site.

Carbon dioxide (CO2): the most common greenhouse gas (other major greenhouse gases include methane and nitrous oxide).  Carbon dioxide is released by burning fossil fuels, land clearing/deforestation and cropping.

Carbon footprint: a form of carbon calculation that measures the amount of carbon dioxide equivalent that a country, a business, an industry or an individual produces or is responsible for.  The footprint calculates the direct and indirect level of CO2-e emissions.  Direct emissions include the burning of fossil fuels for energy and transportation and indirect emissions focus on the whole lifecycle of products from procuring raw materials to waste management.

Carbon neutral: where an individual or company's carbon emissions are effectively reduced to zero through a combination of reducing energy consumption, using renewable energy and offsetting the remainder by (for example) planting trees to absorb carbon dioxide from the atmosphere or building renewable energy power stations.

Carbon offsetting: where an investment is made in a project that will lead to the prevention or removal of carbon dioxide from the atmosphere (for example, planting trees or building renewable energy power stations to avoid the construction of coal ones).

Climate change: a change of climate that is attributed directly or indirectly to human activity that alters the composition of the global atmosphere that is in addition to natural climate variability over comparable time periods.

Direct emissions: emissions of greenhouse gases from sources within the boundary or control of an organisation or facility's processes or actions.  In the World Resources Institute and World Business Council for Sustainable Development (WRI/WBCSD) Protocol these are also referred to as Scope 1 emissions.  Examples of direct emissions include burning of fossil fuels for energy and transportation and emissions from industrial processes.

Emissions Reductions: a measurable reduction in the level of greenhouse gases being emitted by a country, state, organisation or individual.

Emissions trading: a scheme that allows companies to either reduce emissions or pay for the right to pollute (with the money paid being used to reduce emissions elsewhere - often in developing countries).

Energy efficiency: is using less energy to provide the same amount of heating, cooling or other energy service.  Usually refers to cutting energy wastage (like turning off unused lights, plant and equipment).

Fossil fuel: fuel of biological (plant and animal) origin and largely comprised of carbon and hydrogen.  Coal, gas and oil are all fossil fuels.

Global warming: see 'climate change'.

Greenhouse gases: the gases (carbon dioxide, water vapour, methane, nitrous oxide, ozone, and various fluorocarbons) that blanket circling the Earth and which prevent solar radiation from the Sun being reflected back into space.

Greenhouse effect: the effect created by the band of greenhouse gases that blanket the Earth.  The greenhouse effect keeps the Earth's surface within a range and at a level that makes life on Earth (as we know it) possible.

Greenhouse Gas Protocol: the GHG protocol is an international accounting tool for government and business developed by the World Resources Institute (WRI) and the World Business Council on Sustainable Development (WBCSD).  The protocol provides an international standard reporting system that can be used for every aspect of reporting, from national to small business.

Indirect emissions: emissions that are a consequence of the activities of an organisation but occur from sources owned or controlled by another organisation.  In the World Resources Institute and World Business Council for Sustainable Development (WRI/WBCSD) Protocol these are also referred to as Scope 2 emissions.  A company's scope 2 indirect emissions include for example the consumption of purchased electricity, heat or steam and emissions from company owned vehicles.   Scope 3 indirect emissions include transport related activities in vehicles not owner or controlled by the organisation, out sourced activities, air travel and waste disposal.

Kyoto Protocol: an international agreement made in 1997 which sets emission reduction targets for developed countries and establishes mechanisms to reduce the emissions of developing countries.  The Kyoto Protocol is an addendum to the United Nations Framework Convention on Climate Change.  Australia is now a signatory of the Kyoto Protocol.

Renewable energy: energy produced from renewable resources such as wind, solar, geothermal energy and biofuels.

Renewable resources: a natural resource qualifies as a renewable resource if it is replenished by natural processes at a rate comparable to its rate of consumption. Wind, solar, oxygen, fresh water, timber, and biomass can all be considered renewable resources. However they can become non-renewable resources if used at a rate greater than the environment's capacity to replenish them. Renewable resources are used in the production of renewable energy.

Sources:

WWF - Australia

EPA Victoria