‘Heat dome’ to ‘mega-blaze’: Extreme weather terms on the rise

06 August 2021

Published by https://au.news.yahoo.com/

GLOBAL – Extreme weather is forcing climate scientists to find new terms to communicate about our changing planet.

Bushfires, heatwaves, flooding and typhoons have become more severe and as a result, new terms have been devised out of necessity to describe them.

“Mega-fire” came into common usage during the Black Summer bushfires which some believe were Australia’s worst on record, and the term is now being used by some commentators to describe events in the Northern Hemisphere this summer.

Other phrases like “heat dome” have been around for years, but are seemingly being used more frequently now.

Dr Sarah Perkins-Kirkpatrick, who researches climate extremes at UNSW, believes there is growing public interest in the causes of extreme weather.

“People, now have an appetite to understand much more about the dynamics of weather events,” she told Yahoo News Australia.

“We need (new terms) to describe the new events and new things that have started to happen.”

What evidence is there that climate change is responsible?

Professor Will Steffen works with the Climate Council to help Australians better understand the effects of climate change on the planet.

He said that while extreme weather events do naturally occur, it is “basic physics” that by pouring more greenhouse gases into the environment, more heat is trapped.

“That means you have more energy in the lower atmosphere that these extreme events draw on, so using physical principles we understand that’s going to make (extreme weather events) worse,” he said.

Ocean climate facts you may not know

  • Oceans absorb more than 90 per cent of extra heat caused by greenhouse gases.
  • Heat generally pools on the upper oceans, and surface currents can move excess heat from the Pacific Ocean to the Great Barrier Reef.

What is a heat dome?

Heat domes occur during intense high pressure systems which are either stationary or slow moving, and thus maintain high temperatures in a single space for a long period of time.

“The longer the heatwave, the more the heat actually builds up in the atmosphere,” Dr Perkins-Kirkpatrick said.

“You can kind of imagine it being in a saucepan and as the water boils, the heat is contained in that little environment.”

They are likely occurring more frequently due to climate change and can worsen conditions required for mega-fires.

Mega-fires explained

Professor Steffen describes mega-fires as being more intense and covering a larger areas than other bushfires or wildfires.

“Eucalyptus forests are finely adapted and burning is part of their natural dynamics,” he said.

“On average, if you go along the east coast of Australia, where a lot of these forests are, about two per cent of them burn every year, but in the 2019/2020, bushfires 21 per cent of them burnt.

“That’s an order of magnitude more, and why the term mega-fire is probably actually appropriate.”

Key extreme weather terms that are commonly used

  • Tipping cascades are a series of tipping points which can impact each other like a row of dominoes.
  • Marine heatwaves mean excessive underwater heat, and these are affecting areas like the Great Barrier Reef.
  • Super typhoons are more intense and can cause heavy rain and flooding.
  • New normal describes weather trends observed by scientists after studying decades of weather data.
  • Urban heat islands occur in urban areas where there is less vegetation to send water back into the atmosphere, and large areas of concrete and steel which traps heat.

Why the term ‘tipping point’ is being used more often

Tipping point describes features of the Earth’s system which can be pushed to a threshold and tip quickly, and/or irreversibly to create new conditions.

Professor Steffen said an example many people are familiar with is melting sea ice in the Arctic Ocean.

“Once that gets to a critical point, it becomes self reinforcing,” he said.

“It’s simply because you’re reducing the area of ice which reflects sunlight, and uncovering darker ocean water which absorbs sunlight, and that intensifies the heating.”

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