Pacific islands can expect more extremely hot and wet days, saltier oceans killing off coral reefs and rising sea levels, a new report on climate change reveals.
Climate Change Minister Greg Combet released the report while attending the United Nations climate summit in Durban, South Africa.
Regional warming is expected to be greatest near the equator, the report says.
"Large increases in the incidence of extremely hot days and warm nights are also projected.
"A widespread increase in the number of heavy and extreme rain days is projected."
The report adds that conditions for coral reefs will become "increasingly marginal" due to further ocean acidification.
It also warns Pacific islands of rising sea levels of around 18 centimetres by 2040 and 80 centimetres by 2100 in a worst-case scenario for emissions growth and ice cap melting, and around 30 centimetres by 2100 under the best case of emissions growth slowing.
The landmark report, Climate Change in the Pacific, covers three years of research by CSIRO and the Bureau of Meteorology.
"Pacific Island countries and East Timor are extremely vulnerable to climate change," Mr Combet said in a statement.
"Until now, though, understanding of climate change in the Pacific has been limited."
The report includes online tools to help Pacific island countries understand the changes.
It also has country-specific information on 15 small islands states: East Timor, Papua New Guinea, Solomon Islands, Vanuatu, Fiji, Tonga, Samoa, Niue, Cook Islands, Kiribati, Tuvalu, Nauru, Marshall Islands, Federated States of Micronesia and Palau.
Australia is providing more than $328 million under a five-year program to help small nations adapt to climate change.
Meanwhile, the Australian Greens have accused the government of failing to push for an agreement beyond the existing Kyoto protocol, which is due to expire.
Mr Combet told a session of the UN climate summit - speaking on behalf of the "umbrella group" of countries including Australia, the US, Canada, Russia and Japan - that greater investment through a new Green Climate Fund was needed to help developing countries adapt to climate change and tap into low-emission technology.
The minister also called for a new global climate action reporting-and-review system.
A new transparency regime would show whether countries were taking the action they promised and compare their efforts, Mr Combet said.
But Greens deputy leader Christine Milne said Australia was failing to show leadership on the issue of what comes after the Kyoto protocol expires.
It would be "an enormous blow" to climate action globally if the Kyoto protocol was allowed to lapse post-2012 with no legally binding treaty or even a pathway towards one, she said.
"Minister Combet ... pointedly avoided any commitment to a second Kyoto commitment period by talking instead about a more appropriate 21st century agreement," Senator Milne said.
"Now is the time for Australia to offer leadership on the back of the country's renewed credibility thanks to the clean energy package."
UN secretary-general Ban Ki-Moon had urged the summit to consider a second commitment period under the Kyoto protocol.