Scientists have suggested a new classification for storms as tropical cyclones become increasingly severe.

The Saffir-Simpson hurricane wind scale runs 1-5, with five describing near-total destruction. But experts meeting at a conference in New Zealand say there may be a need for a Category 6, as climate change leads to more extreme weather events.

Typhoon Haiyan

In 2013, South-East Asia suffered the strongest storm ever recorded at landfall, with wind speeds of 315km per hour. Typhoon Haiyan left more than 6,000 people dead and nearly 1,800 others missing. The typhoon devastated large portions of South-East Asia, particularly the Philippines; damaging more than a million houses. More than 27,000 people were injured and 4 million displaced.

The typhoon caused such destruction because it reached peak intensity just as it hit landfall; and created a 13-foot storm surge in a bay, headed by the city of Tacloban.

A destroyed house stands in the midst of fallen trees near Guiuan, Eastern Samar, in central Philippines November 20, 2013. The Philippines is facing an enormous rebuilding task from Typhoon Haiyan, which killed at least 3,974 people and left 1,186 missing, with many isolated communities yet to receive significant aid despite a massive international relief effort.  REUTERS/Edgar Su (PHILIPPINES - Tags: DISASTER ENVIRONMENT TPX IMAGES OF THE DAY) - GM1E9BK1KCZ01
A destroyed house stands among fallen trees, in central Philippines.
Image: REUTERS/Edgar Su

Hurricane Patricia

In 2015, Hurricane Patricia hit the coast of Mexico with winds of 265km per hour, making it the most powerful storm ever to be recorded in the Americas. A spokesperson for the Meteorological Organisation, Claire Nullis said that at one point the hurricane’s winds were strong enough “to get a plane in the air and keep it flying”.

The hurricane did not result in the catastrophic damage many had anticipated, as the winds stayed confined to a small area and hit a relatively unpopulated region. Patricia did cause mud slides, flooding and power outages; and forced thousands of people to flee their homes and beachfront resorts.

The damaged roof of a Pemex gas station is seen in Casimiro, Mexico October 24, 2015. Hurricane Patricia caused less damage than feared on Mexico's Pacific coast on Saturday, but little was known about an isolated part of the shoreline dotted with luxury villas and fishing villages, where the storm and its 165 mph (266 kph) winds landed.Thousands of residents and tourists had fled the advance of the storm, one of the strongest in recorded history, seeking refuge in hastily arranged shelters. There were no early reports of deaths and it appeared major damage was averted as Patricia missed tourist centers like Puerto Vallarta and the major cargo port of Manzanillo. REUTERS/Edgard Garrido - GF20000031513
The damaged roof in Casimiro, Mexico, following Hurricane Patricia.
Image: REUTERS/Edgard Garrido

Tropical Cyclone Winston

In 2016, Tropical Cyclone Winston tore across Fiji, killing 42 people. With winds that reached 296km per hour, the cyclone damaged 32,000 houses, leaving hundreds of thousands of people in need of shelter. The Fijian government estimated total losses topped $1.4 billion, with hundreds of schools damaged, basic public services disrupted, and crops and livelihoods destroyed.

At the Pacific Climate Conference in Wellington, New Zealand's Climate Change Minister, James Shaw, said Winston was an example of a cyclone that could have been a category 6. “The only reason it wasn't a category six cyclone is because we don't have a category 6, but we might need one in the future.”

Category 5 was previously considered the highest category necessary because it led to total destruction of human infrastructure. Michael Mann, director of the Earth System Science Center at Penn State University, said that was no longer true due to sturdier buildings.

“Since the scale is now used as much in a scientific context as it is a damage assessment context, it makes sense to introduce a category 6 to describe the unprecedented strength storms we’ve seen over the past few years.”

Mann said category 6 “would also better communicate the well-established finding now that climate change is making the strongest storms even stronger”.

Chris Brandolino, principal scientist at the National Institute of Water and Atmospheric Research in New Zealand, said introducing another category could confuse people.

He said: “Categories are engaging to the public and it’s easy for us to understand and communicate the severity of a storm. I always encourage re-evaluating the science, but I think it requires looking at the whole scale, not just adding a category. Maybe the whole scale gets rejigged to reflect the times.”