Data reliability
We continue to develop our greenhouse gas accounting methods and understanding of issues associated with data quality.
In 2005 an external consultant, Ernst & Young, was commissioned to review Rio Tinto's greenhouse gas inventory process and methodology. This work included an assessment of how Rio Tinto methods compare to established or applicable international standards (such as the WRI/WBCSD protocol). Ernst & Young identified opportunities for improving Rio Tinto’s greenhouse gas and energy use accounting process and methodologies. In 2006 efforts will be made to respond to these opportunities.
The uncertainty of the Rio Tinto total greenhouse gas inventory is between four and eight per cent. However the greenhouse gas trend (year to year) uncertainty is estimated to be less than two per cent. The scientific uncertainty with coal seam methane estimation is a significant source of uncertainty.
In 2001, the Intergovernmental Panel on Climate Change (IPCC) updated their 1996 global warming potential (GWP) values. In some cases GWPs increased (CH4, C2F6) whilst in others the GWPs decreased (CF4, N20). Rio Tinto currently uses the 1996 IPCC global warming potentials. During 2003, an assessment of the change to the revised values was undertaken. It concluded that adoption of the new GWPs would result in a change to the inventory of less than one per cent. Based on the immaterial impact on the inventory, and the fact that international reporting standards (such as the Kyoto Protocol) are yet to adopt the revised GWPs, it was decided that Rio Tinto will continue to use the 1996 GWPs. This decision may be revised in the future if international standards move towards adoption of the 2001 GWPs.
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