State of the Climate - 2012
- 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.
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).
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.
The Bureau has been observing, reporting and researching Australia’s
weather since 1908. CSIRO has been undertaking atmospheric and
marine research for more than 60 years. Together our scientists
continue to build the body of knowledge that allows people to
understand the changes in our climate that we are observing and
prepare for any future changes.