Abstract: In November 2010, Professor Ross Garnaut was commissioned by the Australian Government to provide an update of his 2008 Climate Change Review (http://www.garnautreview.org.au/2008-review.html). This review (see http://www.garnautreview.org.au/update-2011/terms-of-reference.html) was to consider developments in climate change mitigation, climate change science, proposals to develop a carbon price in Australia, trends in domestic and international emissions, changes in low emission technology, the potential for abatement within the land sector and developments in the Australian electricity market. A series of papers related to the above are being released during the period November 2010 to March 2011 with the final report due May 2011. The Centre for Australian Weather and Climate Research (CAWCR - see http://www.cawcr.gov.au/) received a request from the Department of Climate Change and Energy Efficiency (DCCEE) to provide input to this process. This technical report was developed in response to the request. The rationale was to provide from CAWCR a summary of the science of climate change, especially since the 2008 Garnaut Report, and associated national developments in climate change programs. This report was one part of the process that informed Professor Garnaut during the development of his Climate Change Science Report. Essentially this science update is a rapid assessment of material published from 2008 to 2010, designed specifically for consideration by Professor Garnaut in his climate science update. This technical report is based on scientific contributions from both CSIRO1 and the Bureau of Meteorology. It is not intended to be comprehensive in terms of depth or breadth. Rather it is a snapshot of the “state of the science” mainly from the perspective of CAWCR scientific expertise based on peer-reviewed literature. The issues covered relate mainly (but not exclusively) to the scope of Working Group One (WGI) of the Intergovernmental Panel on Climate Change (http://www.ipcc.ch/); i.e. an assessment of the physical and scientific aspects of the climate system and climate change.