Australia is stepping up its pledge to help Pacific nations build climate change and disaster reliance, ahead of international climate talks.

The foreign affairs department has released its long-awaited climate change action strategy without any fanfare, pledging $500 million from 2020-2025 to help Pacific nations.

The figure is a "step up" from the $300 million commitment from 2016-2020, the department says in the strategy paper.

READ MORE Pacific Island nations urge action on climate change at UN

"The world's climate is changing faster than most scientists expected even five years ago," the paper says.

"The impacts of climate change are magnifying a range of challenges for developing countries.

AAP

"For some, including Pacific atoll nations, climate change impacts present an existential threat."

Released a month ahead of the United Nations Climate Change Conference in Madrid, the paper reaffirms Australia's commitment to the Paris Agreement, which the department said "underlines the strength of global commitment to addressing the threats of climate change, including commitments by donor countries to provide support to developing countries in need to address climate change".

READ MORE Australia pledges $500 million to tackle Pacific climate change

The DFAT strategy sets three objectives to make the best use of Australia's aid and development program:

* support partner countries to adapt to climate change, and to plan, prepare for and respond to climate-related impacts;

*promote the shift to lower-emissions development in the Indo-Pacific region;

* support innovative solutions to climate change, including those that engage private sector investment.

Development assistance provided by Australia would be "sensitive to lower-emissions options" and ensure infrastructure or agricultural investments are climate resilient.