That anthropogenic climate change is now of mainstream concern has, paradoxically, a lot to do with an oil man. Maurice Frederick Strong, fossil-fuel magnate, was the founding executive director of the United Nations Environment Programme (UNEP). He died on 27 November.

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Strong was among the last of a generation of post-war scholar-administrators in Canada that included former prime minister Lester B. Pearson. Each lived through the Great Depression and the Second World War, determined that history must never be repeated. Pearson positioned Canada as the world's anti-poverty champion. Strong was one of Pearson's army of nation-builders: he helped to create the Canadian International Development Agency in 1968 and the national oil company Petro-Canada in 1976.

It is thanks to UNEP that nearly every government today has a dedicated department that looks after the environment. The body's creation in 1972 can be attributed directly to Stong's unusual blend of skills. He was adept at making complex science accessible to non-specialists, and able to build unlikely coalitions to support his cause. In 2009, he summarized his approach as, “never to confront, but to co-opt, never to bully but to equivocate, and never to yield”.

Strong was born in April 1929 in Oak Lake, rural Canada, to a family that had fallen on desperate times. As he wrote movingly in his autobiography, Where on Earth Are We Going? (Knopf, 2000), the Great Depression “stripped my father of his livelihood and his sense of self worth. It ruined my mother's health and in the end it killed her”. In winter their clothes would freeze stiff, and at times there was little to eat beyond weeds and dandelions. The need and hunger he witnessed haunted him for years.

Leaving school in 1943, Strong won a cash prize to help with the costs of university but used the money to pay off his parents' creditors. He did not join the ranks of young men headed for the front line. Waiting to board a freight train near his home, he spotted a discarded copy of the local newspaper. He read that Winston Churchill and Franklin D. Roosevelt had decided that once the war was over they would work to unite nations. Strong decided that he wanted to be a part of that project.

For the next two decades he forged what many saw as a contradictory career: that of an oil tycoon. He built companies. Bought companies. Sold companies. He acquired unparalleled knowledge and experience of the energy business; and he became rich. Oil wealth for Strong had a second purpose: it was his passport to Canada's elites. His prominence and ability to make money caught the attention of ministers, and that enabled Strong to realize his public-service ambitions, at home and on the world stage.

In 1969, Strong was running Canada's aid programme when Sweden sought his advice on how to rescue a global environmental meeting. The conference was due to take place in Stockholm in 1972. Few wanted to come, and many of the nations that had signed up seemed to wish the conference to fail.

Developed countries were yet to be convinced that the environmental threat was real. Solly Zuckerman, a former chief scientific adviser to the British government, branded Strong an “extremist”, claiming that environmental degradation was reversible.

Developing nations had different concerns. Some with ambitions to industrialize saw the conference as a conspiracy to keep them poor. “The Third World is not merely worried about the quality of life, it is worried about life itself,” said Pakistan's former chief economist Mahbub ul Haq. And the Soviet bloc was threatening a boycott because the United States wanted communist East Germany excluded from the meeting.

Strong set to work. As the conference secretary-general, he appointed a Soviet scientist to his staff, which gave him a direct line to negotiate with Moscow. And he asked the developing countries to set the conference agenda. This would say explicitly that they could protect their environments without compromising their ability to industrialize, and that rich countries should help to finance poor countries to achieve that goal. To deal with objections from British scientists, Strong sought help from the team at the Massachusetts Institute of Technology in Cambridge that had just published the book The Limits to Growth (Universe, 1972).

He put Barbara Ward, former foreign editor of The Economist turned environmental advocate, on the conference staff to neutralize the influence of sceptical diplomats from rich nations. Somehow, Strong persuaded Indira Gandhi, then-prime minister of India, to open the conference.

The 1972 United Nations Conference on the Human Environment ended in practical action. It led to a new UN body to monitor the global environment, to be based in Nairobi, Kenya. Strong remained UNEP's executive director until 1975. Two decades later, the UN called on him again to steer the Earth Summit in Rio de Janeiro and this resulted in three further agreements: the Framework Convention on Climate Change, the Convention on Biological Diversity and, later, the Convention to Combat Desertification.

Yet Strong's diplomatic ability was not universally appreciated. Many in the energy industry saw him as a closet 'green'; to environmental groups he represented Big Oil. The right, meanwhile, attacked him as the embodiment of Big Government. It is true that UNEP and the environment conventions have made little progress in slowing climate change or reducing the rate of biodiversity loss.

Such failures cannot be attributed to Strong alone. They point to a flaw in the global environmental architecture that he helped to draw up. The world's green agreements need leaders with an unusually broad mix of qualities. Maurice Strong was one of the last. His passing is the end of an era.