CSIRO head Larry Marshall has sought to defend deep cuts to climate science programs after days of sustained criticism, saying global warming research was "one piece of a much larger puzzle" in solving Australia's biggest challenges.

His defence came as dozens of scientists, including some whose jobs are under threat at CSIRO, rallied in Melbourne, warning the cuts would hurt Australia's ability to address the climate change threat.

In a lengthy statement released on Monday, Dr Marshall said there should be a focus on turning inventions into benefit for society and CSIRO had to weigh up where it could have the greatest impact.

The statement followed conference calls between CSIRO executives over the weekend to justify and prioritise the cuts to climate research.

"No one is saying climate change is not important, but surely mitigation, health, education, sustainable industries, and prosperity of the nation are no less important," Dr Marshall said.

Dr Marshall also claimed support for climate measurement, such as air pollution monitoring at the Cape Grim station in Tasmania and ocean research via the RV Investigator vessel, was not under threat. He said the Ocean and Atmosphere division of CSIRO would be reduced from 420 staff to 355.

Stormy times for the CSIRO: On board RV Investigator. Photo: Pete Harmsen

However, those job numbers were immediately challenged by scientists. Penny Whetton, a former senior principal research scientist with CSIRO, said they were misleading "because Marshall is including non-climate areas that are not affected", such as marine resources and fisheries.

"From the climate-oriented parts of [Oceans and Atmosphere], they are currently expected to lose 100 staff," Dr Whetton said. "That's the change that matters."

One senior scientist also took issue with the comment that the RV Investigator and Cape Grim were not under threat.

"Yes, the ship will still be there and used by a variety of people – but who will use it for measuring changes in ocean climate CO2 uptake, etc?" the scientist said.

While climate scientists from around the country had gathered in Melbourne at the Australian Meteorological and Oceanographic Society conference to discussion the latest climate research, the CSIRO cuts loomed over the proceedings.

The CSIRO was listed as a conference sponsor.

During the day a majority of scientists wore blue tape around their arms as a sign of protest. At lunchtime dozens of scientists held a rally outside the Melbourne Convention and Exhibition Centre against the cuts.

"I, and many of my colleagues, find this deeply insulting to us as scientists and our efforts over many years," John Church, a climate scientist and CSIRO fellow.

"Rather than major cuts to climate change science in Australia, what is needed is both a reinvigoration and a refocusing of that research on Australia's future needs."

Dr John Church and other climate scientists speaking to the media about proposed cuts to the CSIRO. Photo: Penny Stephens

In a joint statement released alongside the rally, concerned scientists said the cuts to CSIRO would "seriously undermine Australia's capacity to respond to the challenges posed by climate change."

"The cuts to CSIRO will leave Australia unable to meet certain international research commitments, including commitments stemming from the Paris climate conference," the statement read.

The keynote speaker on ocean warming, CSIRO's Susan Wijffels, criticised the cuts, adding Dr Marshall's comments last week sent a "very poor message to the community" that climate science was not needed.

"The idea that Australia has to choose between having this information and playing a great role in mitigation [of greenhouse gases emissions] we also strongly disagree with," Dr Wijffles said.

"We are one of the wealthiest nations in the world. It seems absurd that we have to choose."

Peter Stott, who heads the climate observation and attribution team at Britain's Met Office, said the proposed cuts were causing concern within the UK weather organisation. Its chief scientist, Professor Julia Slingo, emailed colleagues over the weekend to say they should support CSIRO scientists.

In Canberra, Bureau of Metrology head Rob Vertessy told a Senate estimates hearings the cuts threatened weather data research.