Emissions Reduction Targets and the Great Barrier Reef November 2009 on the level of risk we are prepared to take. More than 100 nations have endorsed the goal of limiting average global warming to no more than 2°C above the preindustrial temperature 3 . Such an average increase, however, will inevitably lead to significant impacts in many locations and on many sectors. For example, highly sensitive systems such as ice sheets, coral reefs, coastal settlements, alpine ecosystems, and regions of marginal agriculture would be under considerable risk even at this warming scenario. A stabilisation level of no more than 450 parts per million in the concentration of CO 2 - equivalent greenhouse gases in the atmosphere could achieve, at best, an even chance of constraining warming below the 2°C target 4 . To achieve even this 50:50 chance of avoiding 2°C of warming would require global emissions to peak no later than 2020, and then decline to 80-90 per cent below 2000 emissions by 2050. To have a realistic chance of achieving this target, emissions from industrialised countries in 2020 need to be reduced by at least 25 per cent relative to their 2000 levels 5 . 3 Malte Meinshausen, Nicolai Meinshausen, William Hare, Sarah C. B. Raper, Katja Frieler, Reto Knutti, David J. Frame & Myles R. Allen. Greenhouse-gas emission targets for limiting global warming to 2 °C. Nature 458: 1158-1162 (2009). 4 England, M.H., A. Sen Gupta and A.J. Pitman. Constraining future greenhouse gas emissions by a cumulative target. Proceedings of the National Academy of Science 106: 16539 –16540 (2009). 5 The Garnaut Climate Change Review: Final Report, Commonwealth of Australia (2008). The State of the Climate “Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.” 1 Scientific research from multiple independent sources indicates that the emission of greenhouse gases by human activities is the primary cause of the observed global average warming of 0.7 o C over the past century 1 . Australia’s land and sea temperatures are currently warming at the global average rate. Furthermore, emissions over the past century have already committed us to a future increase in global average temperature of at least 1 o C 1 . The most recent evidence shows that the climate is changing more rapidly than earlier thought likely 2 . This underscores the need for immediate action to both reduce greenhouse gas emissions caused by human activities that are responsible for climate change, and to adapt to the changes we cannot prevent. “……emissions from industrialised countries in 2020 need to be reduced by at least 25% relative to their 2000 levels.” What target would prevent dangerous interference in the natural and social systems we rely on? This depends not only on scientific assessments but also 1 IPCC (2007) Summary for Policymakers. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Solomon S, Qin D, Manning M, Chen Z, Marquis M, Kaveryt KB, Tignor M, Miller HL (eds.). Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. 2 Steffen W (2009) Climate Change 2009. Faster Change & More Serious Risks. Department of Climate Change, Commonwealth of Australia, 52pp.