A total of 11 basic indicators are used for 128 countries. Definitions of indicators are taken from Esty et. al. (2005), OECD (2005), IEA (2002, 2010, 2011a, 2011b, 2011c, 2011d); World Resources Institute (2006), as well as from the websites of The World Bank, the Environmental Sustainability Index, the Human Development Report, and the United Nations Environment Programme.

Greenhouse gas (GHG) emissions per capita(tons of CO₂ equivalent)

Emissions of total GHG (CO₂, CH₄, N₂O, hydrofluorocarbons (HFC’s), perfluorocarbons (PFC’s), and SF₆), excluding land-use change and forestry. To convert all emissions to CO₂ equivalent, the global warming potential (GWP) is used. GWP is an index used to translate the level of emissions of various gases into a common measure in order to compare the relative radiative forcing of different gases without directly calculating the changes in atmospheric concentrations. GWP is the ratio of the warming caused by a substance to the warming caused by the same mass of CO₂.

Atmospheric concentrations of NO₂ and SO₂(μg/m³ of air)

The values were originally collected at the city level. The number of cities with data provided by each country varies. Within each country, the values have been normalized by city population for the year 1995, and then summed to give the total concentration for the given country. High concentrations decrease air sustainability.

PM10(μg/m³ of air)

Particulate matter concentrations refer to fine suspended particulates less than 10 microns in diameter that are capable of penetrating deep into the respiratory tract and causing significant health damage.

Nuclear waste(tons of heavy metals per capita per year)

Nuclear waste is primarily due to spent fuel from nuclear power plants. It is assumed that nuclear waste influences land sustainability negatively due mainly to generation of heavy radioactive metals.

Access to electricity(percent of population)

Access to electricity is the percentage of population with access to electricity. Electrification data are collected from industry, national surveys and international sources.

Renewable resources production(percent of total primary energy supply)

The higher the proportion of renewable energy sources is, the less a country relies on environmentally damaging sources such as fossil fuel and nuclear energy.

Electricity production from oil, gas and coal sources(percent of total electricity production)

Sources of electricity refer to the inputs used to generate electricity. Oil refers to crude oil and petroleum products. Gas refers to natural gas but excludes natural gas liquids. Coal refers to all coal and brown coal, both primary (including hard coal and lignite-brown coal) and derived fuels (including patent fuel, coke, oven coke, gas coke, coke oven gas, and blast furnace gas). Peat is also included in this category.

Energy intensity(kg of oil equivalent per $1,000 GDP - constant 2005 PPP)

Energy intensity is a measure of the energy efficiency of a nation's economy. It is calculated as units of energy per unit of GDP. High energy intensities indicate a high price or cost of converting energy into GDP. Low energy intensity indicates a lower price or cost of converting energy into GDP. Energy Intensity, as defined here, should not be confused with Energy Use Intensity (EUI), a measure of building energy use per unit area.

Energy use(kg of oil equivalent per capita)

It refers to use of primary energy before transformation to other end-use fuels, which is equal to indigenous production plus imports and stock changes, minus exports and fuels supplied to ships and aircraft engaged in international transport.

Energy imports(percent of energy use)

Net energy imports are estimated as energy use less production, both measured in oil equivalents. A negative value indicates that the country is a net exporter. Energy use refers to use of primary energy before transformation to other end-use fuels, which is equal to indigenous production plus imports and stock changes, minus exports and fuels sup-plied to ships and aircraft engaged in international transport.

References

• Esty DC, Levy M, Srebotnjak T, Sherbinin A (2005) 2005 Environmental Sustainability Index: Benchmarking National Environmental Stewardship, New Haven, CT, Yale Center for Environmental Law and Policy.
• OECD (2005) OECD Factbook 2005, Paris: OECD Publications.
• IEA (International Energy Agency) (2002) World energy outlook: Energy and poverty, Paris: International Energy Agency.
• IEA (International Energy Agency) (2010) World energy outlook 2010, Paris: International Energy Agency.
• IEA (International Energy Agency) (2011a) Energy balances of non-OECD countries, Paris: International Energy Agency.
• IEA (International Energy Agency) (2011b) Energy balances of OECD countries, Paris: International Energy Agency.
• IEA (International Energy Agency) (2011c) Energy statistics of Non-OECD countries, Paris: International Energy Agency.
• IEA (International Energy Agency) (2011d) Energy statistics of OECD countries, Paris: International Energy Agency.
• World Resources Institute (2006) EarthTrends: Environmental information, Washington, D.C.: World Resources Institute.

Websites

• The World Bank
• Environmental Sustainability Index
• Human Development Report
• United Nations Environment Programme