Climate change in Australia
  
Australia's future climate > About the projections > Scenarios
Emissions | |
 
Emissions

We do not know what future greenhouse gas emissions will be, because we can not predict the behavioural, social, political, technological and economic drivers of society. Future emissions are critical in climate projections however, so the Intergovernmental Panel on Climate Change (IPCC) developed a series of possible emission scenarios.

These scenarios are based on four ‘storylines’ – A1, A2, B1 and B2 - that illustrate possibilities for society in the 21st century. The A1 storyline has three subgroups, based on reliance on different energy sources. This gives us 6 scenario groups on which to base our climate projections.

Note: These scenarios do not include additional climate initiatives (e.g. United Nations Framework Convention on Climate Change, Kyoto Protocol).
A1

A future world of very rapid economic growth, a global population that peaks in mid-century and declines thereafter, and the rapid introduction of new and more efficient technologies. Major underlying themes are convergence among regions, capacity building and increased cultural and social interactions, with a substantial reduction in regional differences in per capita income.
A1FI – reliance on fossil intensive energy
A1B – energy generation is balanced across all sources
AIT – energy is generated using non-fossil energy sources and technologies
A2 Society is based on self reliance and preservation of local identities. Fertility patterns across regions converge very slowly, which results in continuously increasing population. Economic development is primarily regionally oriented and per capita economic growth and technological change more fragmented and slower than other storylines.
B1 Global population peaks in mid-century and declines thereafter, as in the A1 storyline, but with rapid change in economic structures toward a service and information economy, with reductions in material intensity and the introduction of clean and resource efficient technologies. The emphasis is on global solutions to economic, social and environmental sustainability, including improved equity, but without additional climate initiatives.
B2 A world in which the emphasis is on local solutions to economic, social and environmental sustainability. It is a world with continuously increasing global population, at a rate lower than A2, intermediate levels of economic development, and less rapid and more diverse technological change than in the B1 and A1 storylines. While the scenario is also oriented towards environmental protection and social equity, it focuses on local and regional levels.
In Climate Change in Australia, the B1 scenario has been used as the basis for a low warming future, the A1B scenario has been used as the basis of a future if we continue with 'business as usual' and the A1FI scenario has been used as the basis for a high warming future.
^ back to top
 
Concentrations

Carbon cycle models are used to convert emissions into atmospheric concentrations, allowing for uptake of emissions by the land and ocean, land and ocean climate feedbacks, and transport and chemical reactions in the atmosphere.

Carbon cycle models give the following estimates of atmospheric greenhouse gas concentrations for 2100:

  • Carbon dioxide concentrations range from 540 to 970 ppm (compared to the 2005 concentration of 380 ppm)
  • Methane concentrations to change by -11 to +112%
  • Nitrous oxide concentrations to increase by 12 to 46%.
  • Tropospheric ozone, hydrofluorocarbons and perfluorocarbons concentrations are projected to increase.
Anthropogenic aerosols (e.g. black carbon, sulfate aerosols, biomass aerosols and organic carbon aerosols) may increase or decrease depending on the extent of fossil fuels use. Carbon cycle models project a reduction in the ability of the land and ocean to absorb anthropogenic carbon dioxide, causing an increasingly large fraction of anthropogenic carbon dioxide to stay airborne.
^ back to top
 
Radiative forcing

Increasing concentrations of greenhouse gases affects the balance between incoming solar radiation and outgoing heat radiation, referred to as the Earth's radiative balance. This balance determines the Earth's average temperature. Radiative forcing is the term given to an externally imposed change in the radiation balance, such as changes in atmospheric concentrations of greenhouse gases.

The SRES greenhouse gas concentrations are converted to a radiative forcing of the climate system using radiation codes (usually located within climate models themselves). Positive forcing warms the Earth, while negative forcing cools the Earth. All SRES scenarios give positive forcing for the well-mixed greenhouse gases, except for methane in the B1 scenario by the year 2100.
^ back to top
 
More Information

Hot topics in climate change: The IPCC climate change scenarios
www.greenhouse.gov.au/science/hottopics/pubs/topic2.pdf

IPCC Special Report on Emission Scenarios [external link]
www.grida.no/climate/ipcc/emission/index.htm

 
 
© Copyright 2007-2008. All Rights Reserved.

Climate change in Australia Site Designed and Developed by Web Initiatives web design
Climate Change in Australia was developed by CSIRO and the Bureau of Meteorology in partnership
with the Australian Greenhouse Office through the Australian Climate Change Science Program
Disclaimer