Climate scientist Professor Will Steffen, who died at the age of 76, has been remembered as a leader of his field, communicator and mentor, whose work paved the way for much of today’s climate policies.

Steffen, who had advanced pancreatic cancer, died on Sunday. During his career he wore many hats, among them emeritus professor at the Australian National University’s Fenner School of Environment and Society. He was also a former executive director of the International Geosphere-Biosphere Programme, the inaugural director of the ANU Climate Change Institute and a science adviser to the Australian government.

The US-born scientist was also an author, contributed to five Intergovernmental Panels on Climate Change assessments and special reports between 2000 and 2018, and was a councillor with the Climate Council. But for many, he was also a friend and mentor. Professor Tim Flannery, a former climate commissioner and chief councillor at the Climate Council, said he was heartbroken at the loss of Steffen.

“He was the most intelligent, kindest, most gentle person,” Flannery said. “He was a great friend and so loyal. He was so desperately needed right now, he was active right until he couldn’t any more.”

CSIRO climate scientist Pep Canadell said one of the things that made Steffen so impressive was his knowledge of complex sciences and the ability to articulate that to those around him, including policymakers, students and other researchers and scientists.

“He was basically a driving force for thousands of networks globally and helped them to move towards directions that were new to everyone in the 1990s,” Canadell said. “He marked the path for today. His work was his life. He gave everything he had. He worked so hard, he was always available and always ready to contribute.”

Professor Frank Jotzo, director of the Centre for Climate Economics and Policy at the ANU, said he was relatively early in his academic career when he crossed paths with Steffen. “He was a big influence for me in my professional life, as a mentor and as a shining example for how to strive for positive impact in society on the basis of scientific insight.”

Australian journalist and author Marian Wilkinson said Steffen had been vital in sharing his knowledge on climate change, especially in the days of climate denialism in Australia.

“He could speak out where other science voices were nervous about coming forward both because [in] the Howard years they had been pretty much ignored and attacked and that the opposition was very, very vocal against climate science and the media was frankly hysterical at times on the issue,” she said.