State of the Climate - 2012

In this article

  1. Greenhouse gases
  2. Publishing History

Publishing History

Page 8 of 8

Key point

  • Fossil-fuel CO2 emissions increased by more than three per cent per year from 2000 to 2010.
  • The concentration of CO2 in the atmosphere in 2011 was 390 parts per million – higher than at any time for the past 800,000 years.
  • The main cause of the observed increase in CO2 concentration in the atmosphere is the combustion of fossil fuels since the industrial revolution.

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Dr Paul Frazer
Dr Paul Fraser, CSIRO atmospheric scientist, speaks about recorded atmospheric changes.

Greenhouse gas concentrations

Global CO2, methane (CH4), and nitrous oxide (N2O) concentrations have risen rapidly during the past two centuries. The amount of these long-lived greenhouse gases in the atmosphere reached a new high in 2011. The concentration of CO2 in the atmosphere in 2011 was 390 parts per million (ppm) – much higher than the natural range of 170 to 300 ppm during the past 800,000 years.

Global CO2 concentrations in the atmosphere increased from 2009 to 2011 at 2 ppm per year. Over the same period, nitrous oxide increased at nearly 1 part per billion (ppb) per year and the synthetic greenhouse gases (CFCs, HFCs and so on) increased at nearly ten parts per trillion per year. Methane has increased by about 6 ppb per year from 2009 to 2011 after a temporary pause in growth from 1998 to 2005.

The temporary pause was due to an overall reduction in methane sources (likely to be a combination of natural gas, agricultural and wetland emissions). The cause(s) of the recent methane increase are at present unidentified, but again likely to be a combination of the above sources.

The relative contributions to the enhanced greenhouse effect from pre-industrial times to 2011, due to the long-lived greenhouse gases, are: CO2 (64 per cent), CH4 (18 per cent), synthetics (12 per cent) and N2O (six per cent).

A graph of fossil-fuel CO2 emissions increased from 2000 to 2010

Fossil-fuel CO2 emissions (orange) increased from 2000 to 2010 at more than 3 per cent per year. The growth from 2009-2010 was 5.9 per cent, reversing a small decline of 1.2 per cent the previous year related to the global financial crisis. Observations of total CO2 emissions (from fossil fuel burning and land-use change – grey) are tracking along the higher end of expected emissions.

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Dr Melita Keywood, CSIRO Atmospheric Scientist
Dr Melita Keywood, CSIRO atmospheric scientist, speaks about the increase of ozone detected in the background atmosphere over the last 20 years.

Carbon dioxide emissions

Carbon dioxide (CO2) emissions account for about 60 per cent of the effect from anthropogenic greenhouse gases on the earth’s energy balance over the past 250 years. These global CO2 emissions are mostly from fossil fuels (more than 85 per cent), land use change, mainly associated with tropical deforestation (less than ten per cent), and cement production and other industrial processes (about four per cent). Australia contributes about 1.3 per cent of the global CO2 emissions. Energy generation continues to climb and is dominated by fossil fuels – suggesting emissions will grow for some time yet.

A graph of 1000-year records of southern hemisphere background concentrations of CO2 parts per million, N2O parts per billion and CH4 measured at Cape Grim Tasmania

1000-year records of southern hemisphere background concentrations of CO2 parts per million (ppm – orange), N2O parts per billion (ppb – blue) and CH4 (ppb – green) measured at Cape Grim Tasmania and in air extracted from Antarctic ice and nearsurface levels of ice known as firn.

 

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Dr Paul Fraser.
CSIRO Atmospheric scientist, Dr Paul Fraser, discusses the findings of research published online on Nature Geoscience on March 12, 2012 centred on a 65-year record of nitrous oxide changes in the Southern Hemisphere. The record is drawn from atmospheric sampling at the Cape Grim Baseline Air Pollution Station, Tasmania, and air extracted from the Antarctic ice sheet. The research will assist scientists to better predict the future for this long-lived greenhouse gas which is increasing with expanding fertiliser use.

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