Majuro: Australia should accelerate its emissions cuts by bringing its target forward by five years, Marshall Islands foreign minister Tony de Brum says, while warning that his tiny Pacific nation was already feeling the effects of climate change.

Mr de Brum's comments came during Opposition Leader Bill Shorten's visit to the Marshall Islands - a vulnerable collection of isolated, small coral atolls in the Pacific Ocean.

Mr Shorten said Labor would embrace more ambitious climate targets for Australia in line with keeping global warming below two degrees.

The Marshall Islands government has been critical of Australia's climate goal to cut emissions by 26 to 28 per cent from 2005 levels by 2030, describing it as weak.

Speaking on a boat trip to the island of Eneko, Mr de Brum said he would be happy if Australia kept the same emissions cut but sought to achieve it five years earlier.

"Well, I think it can be better," he said of the Australian target. "I think if they can move their date from 2030 to 2025 with the same figures, that is a very good beginning."

Moving the goal forward five years would replicate the United States' promised emissions target.

Mr de Brum said the Marshall Islands were holding out for more ambitious long-term emissions targets and bringing current pledges forward would leave the door open for that to happen.

"It is our long-held belief that Australia should play a leading role in the Pacific, and specifically climate change issues," he said.

"Australia is a Pacific island, a big Pacific island, but a Pacific island."

Mr Shorten said Labor was visiting the Marshall Islands to see firsthand the impact of climate change as it formulated its policies.

"We are here to see firsthand the dreadful effects of the rising water levels, the food scarcity, the drought, the storm surges and the extreme weather events," he said.

Mr Shorten said Labor's soon-to-be-announced position on emissions targets would be consistent with delivering Australia's fair share of keeping global warming to two degrees - an internationally agreed target through the United Nations global climate change negotiations.

But despite promising to back more ambitious targets, Labor has not yet articulated exactly what goal it will adopt and refused again on Tuesday to detail further specifics.

The Climate Change Authority has previously recommended that Australia adopt a 2030 cut of 45 to 65 per cent cut to emissions from 2005 levels as part of it making a fair contribution towards the two degree goal.

The Coalition government has previous rejected that proposal as too economically onerous.

Senior Labor figures including Mr Shorten, his deputy Tanya Plibersek and immigration spokesman Richard Marles are on a four-day trip to the Pacific.

The trip started on Sunday in Papua New Guinea, where the country's Prime Minister Peter O'Neill called on Australia to be the lead voice in supporting its Pacific neighbours at the upcoming Paris climate summit.

While Labor says it will embrace more ambitious targets, it has stopped short of backing the overall climate goal most vulnerable Pacific nations want - limiting global warming to 1.5 degrees, which low-lying islands say is necessary to ensure their long-term survival.

Mr Shorten said while the Opposition respected the Pacific nations' push for 1.5 degrees, "Labor is committed to policies that will see Australia do our part to try restrain temperature increase up to two degrees".

Mr de Brum said the ascendancy of Malcolm Turnbull to the prime ministership gave him hope that Australia would offer a more responsive approach to climate change.

The main island on the Marshalls, Majuro, is about about 50 kilometres long. But at its widest it is only about 400 metres, and at many points less than 100 metres.

In the past bodies like the UN Intergovernmental Panel on Climate Change have highlighted the threat of climate change to the Marshalls, finding that about two-thirds of the islands would be inundated with a sea-level rise of 80 centimetres.

But more recent research has found islands from the nearby and similar nations of Kiribati, Tuvalu and the Federated States of Micronesia were in fact remaining stable and even growing in size.

But Mr de Brum was dismissive of the research on growing atoll sizes, saying "to my mind that is the equivalent of people running around saying coal is the future of the world".

He said the Marshall Islands were already feeling the effects of climate change. Freshwater resources were being inundated by sea water, while coastal erosion and seasonal unpredictability were becoming a feature of life in the country.

As the boat moved towards Eneko, Mr de Brum pointed to a rocky patch in the water where he said another island known as Anebok had disappeared in the past 12 years.

The broad sentiment was echoed by the head of the Marshall Islands Environment Protect Agency, Moriana Phillip, who said that many atolls had changed distinctively over the past 10 years.

She said the worst impacts came with strong winds and high tides, which caused the collapse of cement sea walls, sewage spills, and property and cropping land to be inundated with sea water.

The Labor delegation left Majuro on Tuesday afternoon, arriving in another small Pacific island nation, Kiribati, where Mr Shorten will meet with President Anote Tong.

Mr Tong has led a push among some island states for a moratorium on new and the expansion of coal mines and industry to be considered as part of the international climate negotiations.

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