The CSIRO's chief has told the ABC the backlash from his decision to restructure the organisation has made him feel like an "early climate scientist in the '70s fighting against the oil lobby" and that there is so much emotion in the debate it almost "sounds more like religion than science".

Key points: CSIRO chief says he will not back down on restructure

CSIRO chief says he will not back down on restructure Thousands of climate scientists sign protest letter

Thousands of climate scientists sign protest letter Chief says change is about using resources effectively

Dr Larry Marshall said he would not be backing down on his controversial shake-up of the organisation's climate divisions, telling the ABC he was yet to be persuaded.

The redirection of climate science priorities at the CSIRO has drawn international condemnation, with thousands of climate scientists signing an open letter protesting against the changes.

The Oceans and Atmosphere division is expected to be one of the hardest hit, with 60 positions to go through a mix of redeployment and redundancies.

All up, 350 jobs will "change" - a plan that's drawn the ire of an Intergovernmental Panel on Climate Change co-chair and even the World Meteorological Organisation which has made an unprecedented statement condemning the decision.

But Dr Marshall said he had not been persuaded to reconsider the changes.

"For that to happen, someone's going to have to convince me that measuring and modelling is far more important than mitigation - and at this point you know, none of my leadership believe that," he said.

Since the changes were announced last Thursday, Dr Marshall has spent much of the week trying to clarify the restructure, stressing that there will not be a net loss of jobs.

"I feel like the early climate scientists in the '70s fighting against the oil lobby," he said.

"I guess I had the realisation that the climate lobby is perhaps more powerful than the energy lobby was back in the '70s - and the politics of climate I think there's a lot of emotion in this debate.

"In fact it almost sounds more like religion than science to me.

"I've been told by some extreme elements that they've put me at the top of the climate deniers list and what perplexes me is how saying that we're going to shift more resources to mitigation - i.e. doing something to address climate change versus just measuring and modelling it - I don't see how that makes me a climate denier.

"It just seems to me the whole purpose of measurement and modelling the whole purpose of trying to understand climate change is then to figure out what to do about it - that's where we're trying to move to."

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Senate Estimates hearing to scrutinise redirection

Dr Marshall said it was about using resources in the most effective way.

Larry Marshall will again address a Senate Estimates hearing today. ( ABC News )

"I know we have to continue measurements, I know we have to continue modelling and it's not a binary thing - we're not stopping," he said.

"But we do have to scale back in order to redirect resources to mitigation."

It is a redirection that will be closely scrutinised at a Senate Estimates hearing in Canberra today.

Dr Marshall will attend amid criticism stretching from as far as the World Meteorological Organisation's Climate Research Program.

"Normally as a UN agency we would never intervene or interfere like this, but this is just so startling and so devastating that we have to take this stand," director Dr Dave Carlson said.

"Climate is the most complex human challenge that we face.

Creativity, intellectually, engineering wise to try and actually understand the combined biological, ecological, chemical, physical climate system and then to build models to be able to predict what the impact is of what we're doing is one of the premier human intellectual challenges and achievements.

"So this idea that it's something simple and something you turn it on and off and something that's done it does leave us speechless - we're just in awe of how much of a serious misunderstanding that is."

International scientists call for restructure re-think

Thousands of international climate scientists have echoed those concerns - signing an open letter to be sent to the Government and the CSIRO's board urging the organisation to reconsider its decision.

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Former CSIRO oceanographer Paul Durack - who now works at the Lawrence Livermore National Laboratory in the United States - is one of the co-authors.

"We've had over 2,500 independent responses and it's a really overwhelming but an unsurprising international response," he said.

"There are some very profound and very distinguished scientists that are globally recognised that have signed up to this and sent emails to folks involved in putting this together."

Dr Marshall said he understood the concerns - from both abroad and his staff internally.

"I don't blame our scientists for crying out - they're passionate about what they do," he said.

"When a scientist has spent 20 or 30 years working in a particular area, they love it, that's what gets them out of bed in the morning - they're not going to want to change.

"I think this is much more about change and a shift in strategy and a shift in direction than it is specifically about climate - I think this is a fundamental human nature of resisting changing.

"When you really love doing something you don't want to change - we have to be respectful of the scientists that feel that way, but in order for the organisation to move forward, to evolve - we have to be capable of change and shift in direction.

"So now we're going through this process of figuring out who can change, who can't."