There are two kinds of political people in today’s world: a minority who believe that climate change is the most consequential problem humans now face or have ever faced, and a majority for whom, for one reason or another, the penny has not dropped. I once held Malcolm Turnbull in some esteem because I believed he belonged sincerely to the minority. I now realise what a fool I was.

During the 2010 federal election campaign, Turnbull, who some eight months earlier had lost the leadership of the Opposition on the question of climate change, strode onto the stage of a packed Sydney Town Hall at the launch of Beyond Zero Emissions’ Stationary Energy Plan. The person who introduced him mentioned that Turnbull was now a climate-change “pariah” among his political colleagues. Turnbull welcomed the description as “distinctly” a privilege.

To intermittent loud applause, Turnbull argued that there was a hunger among Australians for information about how their country might move “to a situation where all or almost all of our energy comes from zero- or very near zero-emission sources”. Turnbull argued that we must be “guided by science”; that humans were now “conducting a massive science experiment with this planet”, the only one we had; and that in their predictions about the “catastrophic” consequences of climate change the scientists might, if anything, very well be erring “on the conservative side”.

Turnbull pointed out that 2010 was the “warmest year on record”. Although it might not be possible to link each weather disaster with the changes in the climate, “we know” that “extreme weather events are occurring with greater and greater frequency” and that “these trends are entirely consistent with the climate-change forecasts, with the climate models that the scientists are relying on”.

Climate change was a “profound moral challenge”, said Turnbull. It was a profound moral challenge because “we as a human species have a deep and abiding obligation to this planet and to the generations that will come after us”. There was loud applause in the Sydney Town Hall. “In order to discharge that obligation we must make a dramatic reduction in the world’s greenhouse gas emissions.”

Of what order? What was necessary was a 50% global reduction of emissions by 2050 compared to what they were in the late 20th century. “I promise you [that] you cannot achieve that cut without getting to a point by mid-century where all or almost all of our stationary energy … from power stations and big factories and so forth comes from zero-emission sources.”

Turnbull admitted that he had once held out hopes for “clean coal”, by which he and everyone else in 2010 meant burning the coal but then capturing and storing underground the carbon dioxide that was released. He now had grave doubts. The future could equally lie with solar or wind or other zero-emissions technologies. The role of government was to put a price on carbon emissions, provide some modest research and development finance, and then leave it to the market to decide which zero-emissions technologies would win out. One thing only was clear. “The zero-emission future is absolutely essential if we are to leave a safe planet to our children and the generations that come after them.” Cue loud and sustained applause.

In 2010 Turnbull had argued that natural weather disasters were entirely consistent with climate scientists’ models and warnings about future catastrophe, and that the earth’s future rested on the rapid adoption of renewable-energy technology.

In late September 2016, at a time when South Australians were still fighting the effects of wild winds and floods, Turnbull seized upon the opportunity presented not to dramatise the dangers of climate change but to discredit those who believed that the future of the earth and of our children and our grandchildren relied on the progress of zero-emissions renewable technology.

Turnbull lambasted his political opponents for their wildly irresponsible renewable-energy targets. “If you are stuck in an elevator, if the lights won’t go on, if your fridge is thawing out … you are not going to be concerned about the particular source of that power – whether it is hydro, wind, solar, coal or gas.” He continued, “I regret to say that a number of state Labor governments have over the years set priorities and renewable targets that are extremely aggressive, extremely unrealistic.” The “incident” in South Australia was a “wake-up call”.

Ambitious renewable-energy targets – of precisely the kind he championed with apparent conviction in 2010 – now represented for Turnbull the triumph of “ideology”, a political disease to which Labor was prone, over common sense and practical reality. Modest renewable-energy targets were certainly permissible. But only so far as they did not threaten what Turnbull emphasised must always be the “key priority” of his government and indeed of all governments, namely “energy security”. For Turnbull in 2016 energy security was more important than any nonsense about the zero-emissions targets that Turnbull in 2010 argued were vital.

In October 2016, Turnbull was in Brisbane, touting the virtues of legislation aimed at preventing environmental groups from taking legal action against fossil-fuel developments. During a radio interview, the ABC’s Steve Austin put to Turnbull the arguments of the Queensland Resources Council. According to the council, the export of coal should be actively encouraged, because Australia produced “some of the cleanest coal in the world … [which] burns at a far cleaner rate, [with] less sulphur etc”. “Is that,” Austin asked Turnbull, “how you see it?”

As it turned out, indeed it was. “The reality is that Australia’s coal compared to that from other countries is relatively clean,” said Turnbull. “The fact is if we stop all our coal exports tomorrow, you would simply have more coal exported from other countries … that would be filling the gap … Trying to strangle the Australian coal industry is not going to do anything … to reduce global greenhouse gas emissions.”

“Coal,” said Turnbull, “is going to be an important part of our energy mix – there’s no question about that – for many, many, many decades to come.”

In 2010 Malcolm Turnbull had serious doubts about the viability of what clean coal then meant – that is to say, carbon capture and storage. By 2016 he had no doubts that a certain kind of coal, serendipitously found in Australia, could be burned comparatively safely without capturing and storing the carbon released, and could thus reasonably be described as clean.

In 2010 Turnbull thought that we were recklessly conducting a dangerous experiment that was imperilling our planet, and that the only prudent course was to reduce the emissions of stationary energy sources to zero by 2050. By 2016 he was criticising the state Labor governments as ideological zealots because of their ambitious renewable-energy targets.

Even more significantly, the man who in 2010 believed zero emissions for stationary energy was vital and achievable by 2050 was by 2016 cheerfully embracing the idea that coal would be part of the world’s energy mix, not for “many decades”, or even “many, many decades”, but for “many, many, many decades” into the future. Many, many, many decades is, by any calculation, a very long time. Turnbull did not show the slightest alarm at the thought that our species would be burning coal, preferably Australian coal, for our energy needs well into the 22nd century.

The zero-emissions pariah had seamlessly become the fossil-fuel realist-cum-enthusiast in the space of six short years. In its own way, this was a remarkable achievement.

There is no need to argue why this metamorphosis has occurred. Everyone who follows Australian politics knows the reason: ambition. Without repudiating his earlier climate-change views, Turnbull would never have become prime minister of Australia. What is more interesting is what it reveals about his character.

Even when I still kind-of admired Turnbull, I had my doubts about him. How could someone, I wondered, who entered Australian politics as a supposedly passionate republican lose all apparent interest in the cause very shortly after the defeat of the referendum proposal, which he argued had broken Australia’s heart?

I now think that this provides a clue. Malcolm Turnbull is a barrister by training and inclination. For him, causes are quasi-clients that he voluntarily and serially embraces – with the kind of sincerity barristers must routinely muster in a court of law – in order to advance his career. At a certain moment, however, Turnbull appears to realise that this or that cause poses a danger to his progress. At this moment, the cause is quietly dropped, with as much dignity and disguise as possible. It is dropped because in the end there is only one cause that ultimately counts for him – the cause of Malcolm Turnbull. Perhaps almost all successful politicians have this quality to some degree. But with Turnbull, it appears to be definitive.