In the 5 years since SoE 2011, international climate science has advanced significantly. The IPCC, operating under the United Nations, is the leading international scientific body for the assessment of climate change. Its role is to review, assess and synthesise the latest information on climate change, based on the most recent peer-reviewed literature. AR5, which cited more than 9200 scientific publications and contained contributions from more than 600 authors (Stocker et al. 2013b), confirms (with between 95 and 100 per cent certainty) that humans have been the dominant cause of warming since the 1950s.
Although it is clear that the climate is warming, the complexity of the climate system means that there are still scientific uncertainties about how much the climate will change in the future. In particular, uncertainty exists about:
- future emissions and levels of GHGs, which will be influenced by policies, and population and technology changes
- the precise temperature response to future GHG concentrations, because climate model projections under different GHG emissions scenarios can only estimate temperature increases within a probability range
- how land and ocean carbon sinks will operate in a warmer climate.
With the long-term global investment in climate science (e.g. the large number of climate observation programs and studies), the increased sophistication of Earth system models and increased understanding of some climate processes, the scientific understanding of climate change impacts has increased substantially since 1990. However, to reduce uncertainty further, this investment must continue, because high-quality information about climate change is a core requirement for good adaptation and mitigation policy (Garnaut 2008).
The National Framework for Climate Change Science (established in 2009) outlined the climate science challenges to be addressed in supporting Australia’s climate change policy, as well as the capabilities required to deliver this science. The plan for implementation of the framework was established in 2012 and set out a series of key policy questions that, when answered, would deliver national benefit. The plan coordinated the science delivered through the Australian Climate Change Science Program, to which the Australian Government committed $15 million per year between 2011 and 2015. A major achievement of the program has been the development of ACCESS (see Box ATM4). In 2015, the 26-year program was replaced with the National Environmental Science Programme’s Earth System and Climate Change Hub ($23.9 million across 5 years).