Observed maximum temperatures for Monday, 13th January, 2014. Image from BOM.
Observed maximum temperatures for Monday, 13th January, 2014. Image from BOM.

By Claire

I’m writing this post from hot hot Canberra, Australia, in my office, in front of my desk fan. In case you didn’t pick up on it, IT’S FREAKING HOT HERE!!!

This week, a large mass of warm, desert air is slowly making its way across southern Australia, bringing as many as five consecutive days above 40°C (104°F). Here in Canberra, we are forecast to swelter through five consecutive days over 38°C (100°F).

Pilot heatwave forecast, beginning the 14th January 2014. Courtesy of BOM.
Pilot heatwave forecast, beginning the 14th January 2014. Image from BOM.

The Bureau of Meteorology (BOM) is currently piloting a new “heatwave forecast” product, in an attempt to better warn people of upcoming heatwaves. In the process of producing this product, they had to create a definition of a heatwave (a nationally used term has not previously been defined). A heatwave, now officially, is, “three days or more of high maximum and minimum temperatures that is unusual for that location.”

Candles melted by the heatwave in Adelaide. Image from abc.net.au
Candles melted by the heatwave in Adelaide. Image from abc.net.au

The fact that the Bureau of Meteorology has created a product specifically for heatwaves is an indicator of the fact that heatwaves in Australia are expected to become more common in the future.

According to the long-term average, Canberra is only expected to experience five days a year with temperatures over 35°C, with severe heatwaves only hitting once every 25 years or so. This week’s heatwave will be the third such event over the last four years. By 2070, scientists expect Canberrans to suffer through between 10 and 18 such days, or, allowing for all uncertainties, between 8 and 26 days.

5-you-don-t-know-hot-australia-memeWith 2013 officially confirmed as the hottest year on record for Australia, 2014 is already shaping up to be another warm one.

Meanwhile, in the USA… The “Polar Vortex”

By Jen (guest blogger)

In recent weeks, we’ve been hearing a lot of media coverage about the frigid conditions gripping the interior United States.  Real-feel temperatures in the Midwest dropped to less than -28°C (-20°F) (however temperatures got as cold as -50°C (-60°F) in places).   The fearsome descriptions of the “Polar Vortex” evoke images reminiscent of the freak super-storms from the movie, The Day After Tomorrow, which sent Americans scurrying across the Mexican border.

Super-storms from The Day After Tomorrow Image:  Day After Tomorrow
Super-storms from The Day After Tomorrow Image: Day After Tomorrow

Well, news flash for the news media:

The polar vortex is not some brand new freak storm, threatening to freeze over the Northern Hemisphere.  Actually, the polar vortex, or circumpolar vortex, is a persistent cold air mass in the Arctic bounded by a west-to-east current in the upper atmosphere, which usually spins on its merry way, unnoticed by Earth’s inhabitants at the surface.

Image: NOAA NWS
Image: NOAA NWS
Frozen car handle breaks off. "Curse you polar vortex!!"
Frozen car handle breaks off. “Curse you polar vortex!!”

Occasionally, the spinning current may weaken, as it did in early January as a result of a warming event high in the atmosphere.  This caused a southward dip in the jet stream that allowed some of that cold Arctic air to slip down into North America.  Though temperatures rose again last week, another wobble in the circumpolar vortex is forecast to generate another cold spell in North America this week.  It’s not expected to be as severe as the first round, but I expect that the media will continue to enjoy the use of their new buzzword for another week or two.

Niagara Falls freezes due to the extreme cold conditions. Photo: Reuters
Niagara Falls freezes due to the extreme cold conditions. Photo: Reuters

The “polar vortex” coverage has, of course, ignited the climate change debate again.  It’s a fair question to ask what climate change might mean for the circumpolar vortex.  The strength and stability of the polar current and the jet stream are dependent on the temperature difference between the poles and the equator.  The stronger the difference, the more stable the current.  As global temperatures climb, polar temperatures climb faster.  This will decrease the temperature difference, which could cause the circumpolar current to destabilize more frequently.

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