Pam was certainly a monster , with one-minute winds reaching 145 knots (268 km/h) and its core pressure dropping below 900 hectopascals - a rare event on both counts in the region.

Still, according to the US ratings – slightly tougher than Fiji and Australia's - Pam's intensity did not make it "an outlier among category 5 storms", says Professor Peter Hoeppe, head of Geo Risks Research for giant re-insurer, Munich RE.

"Starting from Pam there is no need to introduce a new intensity category 6," Hoeppe says.

Well, at least not yet.

As Jonathan Nott, a professor at James Cook University, told Fairfax Media this week, there has "been a lot of discussion over the last five to 10 years" about the need to extend the severity category beyond the current top rating of category 5.

"Everyone's been asking this question: should we have a cat-6 or not?" Professor Nott said.

The reason the debate is likely to revisited is that warming trends point only one way as we pump ever more greenhouse gases into the atmosphere.

Global temperature records continue to tumble. 2014 was likely the hottest year on record and even the past three months set a high for the December-February period as the warmth extends into 2015, the US National Oceanic and Atmospheric Administration said this week.

That warmth doesn't remain at the surface but mostly ends up in the oceans, providing the energy source for storms.

"It's very simple physics," Professor Matt England, a climate scientist at the University of NSW, says. "A warmer ocean leads to a more intense cyclone."

"The model projections show a robust increase of those category 4 and 5 strength storms," he says. "You're loading the dice for a much greater chance of a higher intensity storm."

Assessing cyclone strengths is challenging as  ground stations in the maw of a storm are often damaged. Satellite readings show Pam probably fell just short of the intensity of Cyclone Zoe in 2002, considered to be the strongest in the South Pacific.

Nott of James Cook University, though, has also investigated Cyclone Mahina, the most deadly storm in Australia's recorded history.

Evidence from the March 5, 1899 event, such as a nine-metre storm surge that contributed many of the 300 fatalities, implies the pressure dropped as low as 880 hPA, exceeding both Pam and Zoe.

(Mahina crossed the Queensland coast near Bathurst Bay, not far from where Cyclone Nathan, a severe category 4 storm made landfall on Friday morning.)

Interestingly, climate models predict fewer cyclones for Australia with global warming because there are likely to be more El Nino years.

During El Nino events, waters are relatively warm in the central and eastern Pacific, shifting the "nursery of cyclones" further to the east in those years.

That means places such as Vanuatu may get fewer cyclones but countries such as Fiji and the Cook Islands cop more direct hits, says Professor Steve Turton, a climate researcher also at James Cook University.

Other basins, such as the north-west Pacific, are likely to get the worst of the new world.

"The typhoons will become more common and more severe, which will be a big issue for countries like the Philippines for disaster management," Turton says.

Munich RE's Hoppe says among the biggest cyclones recorded only one had winds intense enough to reach the far end of category 5 and potentially lie with category-6 range: typhoon Haiyan with its 315 km/h winds which killed more than 6000 in the Philippines in 2013.

"There is definitely something changing with the intensity - we are seeing more of the stronger typhoons, cyclones and hurricanes," he says. "But it's not such a big change that we have to change the system."