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During the 4 July address, delivered by his long-time collaborator Professor Johan Rockströmfrom the University of Potsdam,  Steffen was fondly remembered not just as a brilliant scientist, but as a selfless mentor and gifted communicator. 

“I know I speak on behalf of the global sustainability and climate science community in saying that we owe so much to our dear colleague and friend Will Steffen,” Rockström said. 

“His work is now at the frontier of cutting-edge earth systems science.” 

��������Provost and Senior Vice-President, Professor Rebekah Brown, said that Steffen’s contributions to climate science are “unparalleled”. 

“He was a pioneer in earth systems science, synthesising and broadcasting ideas that were once seen as radical but are now considered mainstream,” she said. 

“He had a unique ability to see the connections between distinct scientific disciplines, and how this could be leveraged to address the environmental challenges of our time.” 

In his lecture, Rockström outlined the work he did with Steffen on the planetary boundaries framework, which presents a set of nine planetary boundaries within which humanity can continue to develop and thrive for generations to come. 

“The framework was not initially published as a finalised theory — it was a challenge to the world to scrutinise the nine planetary boundaries that we proposed,” Rockström said.  

“Will then updated this research in 2015, quantifying six of the nine boundaries. He was a fantastic spokesperson for the science. 

“Today we feel more confident than ever that if we are stewards of these nine planetary boundaries, we have a good chance of handing over to future generations a planet with good life support and healthy resilience. 

“But Will and I also wanted to explore what happens when we transgress these boundaries, for example, if we burn fossil fuels to a point where we reach two degrees of human caused global warming, what will the planet’s response be? 

“The conclusion was that already at two degrees warming we risk bumping up that warming to 2.4 degrees just through earth systems feedback of a planet that is losing resilience — and at that point you risk causing a domino effect.  

“The presentation of this work required courage, and Will really represented intellectual robustness combined with courage. 

“He is very much alive in our academic endeavours today. Humanity should thank him as well.”  

Several of Steffen’s close colleagues also took to the stage to speak about his legacy, including Professor Emerita and Pro-Chancellor at Macquarie University, Lesley Hughes, Professor Brian Walker and Distinguished Honorary Professor Penny Sackett.

The full lecture is available to view on