Globally renowned Australian climate scientist Prof Will Steffen has died, aged 75, with former colleagues and family remembering him as an inspiring, courageous and gentle human.
Steffen died in Canberra hospital on Sunday evening after almost a year of treatment for pancreatic cancer.
Colleagues from around the world described him as a scientific giant who had spent a career studying and communicating the risks of climate change.
Steffen was known for his studies on the rate humans were driving changes to the planet and the risks of irreversible “tipping points” that could push the world to “hothouse” conditions.
He was known as a skilled communicator, delivering countless public talks and interviews to the media, and was a trusted adviser to the Gillard government.
The director of the Potsdam Institute for Climate Impact Research in Germany, Prof Johan Rockström, said: “Such a loss for humanity. There is no better friend and colleague for humanity and a livable planet.”
Steffen moved to Australia from the US in 1977, taking a post-doc position at the Australian National University. He was a pivotal figure and leader in coordinating international research collaborations.
Sign up for Guardian Australia’s free morning and afternoon email newsletters for your daily news roundup
In Australia he was a highly respected adviser on climate change policy and worked on a multiparty committee around 2010 that helped devise a mechanism to put a price on carbon.
Steffen was part of a group of scientists including Rockström who described nine “planetary boundaries” that regulate the planet and formed the basis for a Netflix documentary narrated by Sir David Attenborough.
His wife of 51 years, Carrie Steffen, said: “He was a wonderful, kind and passionate man and he was the same as a husband.
“He was the most marvellous companion and the best dinner companion I would ever have, and ever will have. He brought the world to me.”
She said Steffen had been determined to fight the cancer and had undergone chemotherapy and radiotherapy in readiness for surgery.
“He fought this to the end,” she said.
After complications from an initial surgery, he did not regain consciousness from a second operation and died peacefully with Carrie and his daughter, Sonja, 36, by his side.
Carrie said in later years, Steffen had been particularly proud of his work supporting young climate activists, including providing expert testimony in court cases.
Arrangements were still being made for a private funeral ceremony, but Carrie said she also hoped for a larger “knees up” to celebrate his life.
The climate change and energy minister, Chris Bowen, said “very few people around the world could claim to have done more to tackle climate change” than Steffen.
“He was a first class scientist and a world class communicator,” he said in a tweet.
Prof Lesley Hughes, a board member of the government’s Climate Change Authority, said the world had lost “someone truly special” and she had lost “a wonderful friend”.
Dr Pep Canadell, a climate scientist at CSIRO, said one of Steffen’s biggest contributions was as a pioneer in developing a role that combined scientific expertise with coordinating international networks that, he said, had influenced the scientific agenda and governments around the world.
Canadell said: “I was incredibly sad when I heard – no matter how much I knew it was coming. He has impacted so many people, programs, research agendas and governments.”
Former Australian chief scientist Penny Sackett said Steffen was an “irreplaceable scientist, world citizen and friend” who was “courageous in his truth telling”.
“We’ve lost a truly leading thinker on climate change, someone who made a difference in how the world understands it,” said Prof Frank Jotzo, a climate economist at ANU.
Steffen was a member of the government-backed independent climate commission launched in 2011 by the then Labor government, that was closed down in 2013 only to re-emerge as the not-for-profit Climate Council.
The chief executive of the Climate Council, Amanda McKenzie, said: “Our dear colleague Will Steffen contributed enormously to climate science, climate communications and putting the issue on the agenda here and around the world. He helped to build the Climate Council, like many other institutions, from the ground up.
“We will always remember his bravery, his optimism, his kindness, his energy and his determination. We are devastated that he is gone, but determined that his legacy will live on every day in our work.”
In a hand-written letter in 2020 for a project that asked climate scientists how they felt about the future, Steffen wrote: “I’m angry because the lack of effective action on climate change, despite the wealth not only of scientific information but also of solutions to reduce emissions, has now created a climate emergency.
“The students are right. Their future is now being threatening by the greed of the wealthy fossil fuel elite, the lies of the Murdoch press, and the weakness of our political leaders. These people have no right to destroy my daughter’s future and that of her generation.”
