Sources of greenhouse gases

Posted: 1 April 2009

The climate system has inherent natural fluctuations in which global cooling and warming occur. Natural factors like volcanic eruptions and El Nino alter the climate system; however, since the turn of the 20th century, the quantities of greenhouse gases from human actions pumped into the atmosphere have increased substantially, feeding into global warming.

Historic emissions

  • Industrialized countries have emitted the majority of historic carbon dioxide emissions, with 25 per cent of emissions coming from the United States.

CO2 emissions share
CO2 emissions share
Source: Alice McKeown and Gary Gardener, Climate Change Reference Guide and Glossary, in State of the World 2009: Into A Warming World, (Worldwatch Institute)

Sources of today’s emissions

  • Based on Worldwatch Institute estimates, burning of fossil fuels emitted a total of nearly 30 billion tonnes of carbon dioxide (CO2) in 2007, a 36 per cent increase from 1990 levels.
    • The United States emitted 6.1 billion tonnes of CO2 in 2007, a 27 per cent increase from 1990 levels.

    • China emitted 5.9 billion tonnes of CO2 in 2007, a 157 per cent increase from 1990 levels.

    • The European Union (EU-27) emitted 3.8 billion tonnes of CO2 in 2007, a 6 percent increase from 1990 levels.

    • India emitted 1.5 billion tonnes of CO2 in 2007, a 132 per cent increase from 1990 levels.

    • The entire continent of Africa emitted 1.2 billion metric tons of CO2 in 2007, an 84 per cent increase from 1990 levels.
  • Estimates of total 2006 emissions (including not only fossil fuel combustion but also natural gas flaring and cement production) from the Netherlands Environmental Assessment Agency show China surpassing the United States as the leading emitter of greenhouse gases.

  • In 2004, carbon dioxide accounted for 76.7 per cent of global emissions resulting from human activities, or anthropogenic emissions. Use of fossil fuels and land use change are the primary contributors to the carbon dioxide emissions.

  • Methane emissions made up 14.3 per cent of global anthropogenic emissions in 2004. Agriculture and fossil fuel use are the primary contributors of methane emissions.

  • Nitrous oxide emissions made up 7.9 per cent of global anthropogenic emissions in 2004. Agriculture is also the primary contributor of nitrous oxide emissions.

  • The three other greenhouse gases under Kyoto Protocol – sulphur hexafluoride (SF6), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) – are also grouped together into the F-gases. Together, they made up 1.1 per cent of global anthropogenic emissions in 2004.

Global GHG emissions
Global GHG emissions
Source: IPCC, Climate Change 2007: Synthesis Report

Related links:

Fossil fuels and carbon emissions (Renewable energy section)

IPCC, Climate Change 2007: Synthesis Report Netherlands Environmental Assessment Agency

Janos Maté, Kert Davies, and David Kanter, The Risks of Other Greenhouse Gases, in State of the World 2009: Into A Warming World, (Worldwatch Institute)

Dennis Clare, Reducing Black Carbon, in State of the World 2009: Into A Warming World, (Worldwatch Institute)