Fifteen of Australia’s top climate experts explain how we know humans are altering the atmosphere and why we must act now.

1. The global average temperature has increased by about 0.8 degrees since 1850, with most of the increase occurring since 1950. The warming varies among decades because of natural fluctuations but the overall trend has been inexorably upward.
2. The dominant cause of the warming since about 1950 is the increase in the atmospheric concentrations of greenhouse gases released by human activities, of which carbon dioxide (CO2) is the most important.
3. Warming will increase in future, if emissions of CO2 and other greenhouse gases maintain their present paths. “Business as usual” scenarios for future emissions lead to likely global temperature increases of up to six degrees above present temperatures by 2100.
4. Climate change cannot be reversed for many centuries, because of the massive heat stores in the world’s oceans. Even if CO2 and other greenhouse gas concentrations were stabilised today at their present levels, a further warming of at least 0.6 degrees would inevitably follow (on top of the 0.8 degrees observed since 1850) and sea-level rise would continue for centuries to millenniums.

These four conclusions have been known and agreed among thousands of independent climate scientists for more than a decade. However, new findings suggest that the situation is, if anything, more serious than the assessment of just a few years ago.

Click here to read the full article titled “Climate change poised to feed on itself” published in the Sydney Morning Herald by Michael Raupach and John Church, CSIRO; David Griggs, Amanda Lynch and Neville Nicholls, Monash University; Nathan Bindoff, Antarctic Climate and Ecosystems Co-operative Research Centre; Matthew England and Andy Pitman, University of NSW; Ann Henderson-Sellers and Lesley Hughes, Macquarie University; Ove Hoegh-Guldberg, University of Queensland; Roger Jones, Victoria University; David Karoly, University of Melbourne; and Tony McMichael and Will Steffen, Australian National University.