Climate change impacts - A summary of the methodology used
Developing refined projections for NSW has involved:
- determining and using only those global climate models that appear to be the best at assessing climate
- developing predictions of regional climate change and its impacts in NSW, based on a greenhouse gas emissions scenario that reflects the latest emerging trends in emissions.
Assessing the best models for predicting climate - to develop projections that are specific for NSW regions, researchers at the Climate Change Research Centre UNSW, led by Professor Andy Pitman (an Intergovernmental Panel on Climate Change (IPCC) lead author and an expert on climate model evaluation), evaluated existing IPCC global climate models to assess which were better at depicting the existing regional climate.
The four models that were best at depicting existing climate in south eastern Australia were also assumed to have higher skill in projecting future climate.
Regional projections have been based on the outputs of these four best-performing models.
Using emerging trends in greenhouse gas emissions - regional projections are based on an upper-range emissions scenario (the A2 scenario).
The A2 scenario predicts that greenhouse gas emissions will be in the upper-range of the emission scenarios developed by IPCC. This scenario has been chosen for regional assessment work in NSW because it is consistent with emerging climate trends of higher greenhouse gas emissions.
To model future climate change, assumptions are made about future greenhouse gas emission rates and the atmospheric concentrations of greenhouse gases. The IPCC has developed a range of potential emission scenarios for use in climate change models, which are intended to portray a plausible set of future economic and social conditions. In brief, these scenarios are divided into two groups of scenarios (‘A’ and ‘B’) with a different emphasis on economic growth and uptake of emission reduction technologies.
The ‘A’ scenarios lead to higher greenhouse gas emissions and subsequent temperature change. The ‘B‘ scenarios result in lower emissions and temperature change.
Given that global greenhouse gas emissions are currently tracking above the highest emissions scenario developed by the IPCC, the climate projections in this project are based on the A2 scenario, which is an upper-range emissions scenario.
Further detail on the IPCC scenarios can be found in the IPCC’s Fourth Assessment Report.
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