Details of the warning will be outlined in the annual climate change statement to parliament in Canberra on Thursday.
The statement notes rising global temperatures present "unprecedented challenges" to national security.
"Climate change is likely to accentuate economic factors already fuelling political instability, with intrastate conflict, population displacement, food insecurity and civil unrest having risen in the past decade," the statement says.
"Infrastructure failure, extremist activity and disruptive protests could compound the impacts of disasters, water shortages or food and energy price spikes, and further erode some countries' political legitimacy."
Domestically, events such as floods and bushfires - which have in the past caused coal-fired power plant shutdowns and threatened transmission lines - place increased strain on Australia's energy networks.
"This fragility could be used as a climate change-based force multiplier for hostile actors," the statement says.
"The threshold for damage to Australia's energy networks from sabotage may be significantly lower during high demand/low supply periods, such as extreme weather seasons."
The statement also notes potential disruption to global supply chains and greater demand for spending on diplomacy and aid as countries prepare for natural hazards.
Climate Change Minister Chris Bowen, who will speak to the report in parliament on Thursday, said extra stress could be placed on Australia's crisis management agencies, stretching their emergency capabilities.
"The relationship between the level of warming and the threats faced is not linear - the threats will compound and expand exponentially the hotter the planet becomes," he will say.
"Climate change is an existential national security risk to our Pacific partners and presents unprecedented challenges for our region.
"It is likely to accentuate economic factors already fuelling political instability, including risks to water insecurity across the globe."
Australia is working with Pacific leaders as well as the US and UK on the security challenges from climate change.
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