Public servants have previously been instrumental in the nation's climate change policies. They played a major role in advising on and developing carbon pricing mechanisms, and thinking of ways to reduce Australia's greenhouse gas emissions at the lowest overall cost to the economy. Public servants were visible contributors to these policies. Importantly, their contributions were visible to the public.

That visibility has diminished over time and it's harder now to tell what work the public service is doing on climate change policy. The little information senators were able to glean at estimates did reveal a few things.

First, Treasury has not modelled the effects of climate change and emissions reductions on the nation's economy for years.

Second, the Industry Department has led the development of the net zero plans and was responsible for the modelling underpinning them, with some assistance from Treasury, ABARES and Productivity Commission staff.

Third, McKinsey provided research and the consultancy firm won that contract over the government's scientific body, CSIRO.

The public is waiting to see the modelling behind the net zero policies - the delay, the Industry Department says, is so it can present the findings in a way that's easier for people to understand. Prime Minister Scott Morrison said this week it would be released soon.

Until the government releases the modelling, we only have the scant information gained at estimates, and the word of public servants and ministers, that the public service played an important role in the climate policy work. There seems little chance more will be revealed through the slow and obstructive channels of the freedom-of-information system. In any case, the involvement of a private firm, McKinsey, in modelling might encourage FOI officers to claim the documents can't be released due to their commercial value. It will be on journalists, and MPs, to push for the information regardless.

Knowing the extent of the public service's involvement in developing Australia's climate policies will help answer some fundamental questions ahead of the election. Some commentators have drawn attention to the political tinge of the Coalition's net zero document. Many question whether it can actually be labelled a plan in the first place, given its level of detail. The input of the public service gives credibility to policies. Right now, the government's net zero plans are struggling to gain trust, in an election the Coalition wants to make about trustworthiness.

The other question at play is whether the public service still has enough scope to inform policy, and advise meaningfully on climate change action. There's nothing inherently wrong with seeking different sources of advice. It's a matter of getting the right balance, and of making sure the public service is still an attractive place to work for the best and brightest. If the most important work is going to consultancy firms, is there enough reason to stick around in government departments? Is work going to the private sector that public servants should be able to do? Ministers need to answer those questions.

In a recent interview, I asked Howard-era secretary of the Department of the Prime Minister and Cabinet, Peter Shergold, more generally whether the public service was still a good place for people to work if they wanted to contribute to climate change policy.

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Every public servant makes a choice, he said. Will they be more effective working inside the bureaucracy - with its various constraints and opportunities - or outside it? He had to make that decision, too. For five years before becoming a public servant he had been active in advocating on migration and multicultural policy.

"You had to decide where you thought you were more comfortable and where you could be most effective," he said.

"I made a decision which I never regretted, that for all the constraints of working within the public service, I could have greater influence there, than being a much more public and strong voice, outside the public service."

Professor Shergold said he would still advise young, up-and-coming, bright people to have a go at working within the Australian Public Service to have an impact.

"And then if you decide that that is just too difficult, in terms of your commitment, then step back outside," he said.

"I would not say to anyone, 'Well do not go into the public service because you are frustrated at how little progress is being made on climate change policy'. Because, in my view, one thing you learn in public service is governments change, prime ministers change, ministers change, public viewpoints change. And so there are often unexpected opportunities that can be seized to work with government to bring about reforms."

The public service might well be quietly working on climate change policies with the view that a different, future government may embrace them. Those ideas might see the light of day then. Until that time, the public has some Industry Department modelling to read, hopefully soon.