"Is this a real thread or a game?"
Both. The real thread is about understanding how the Earth's climate system works. The game is "Goad the Denier".
I usually manage to avoid rising to the bait, but lost it yesterday. Sorry Nia, I apologize for getting shirty with you, I should know better.
"Pointing to local cold spells as counterevidence is just bad practice."
On the contrary, understanding the causes of extreme weather helps us understand how the climate system works. Climate is after all, the integral of weather. But thanks for the quote, I'll redeploy it whenever the people on your side of the debate point to heatwaves or ten year droughts and ascribe them to 'catastrophicanthropogenicglobalwarmingclimatechange'.
I'm not certain, but I think there may be a severe blast of late winter cold about to hit the southern hemisphere around Australia. South America has been in the grip of deadly cold anyway, but Austalia may be about to get a dose of it too.
Sudden stratospheric warming events are quite rare in the southern hemisphere, because of the stability of the circumpolar southern ocean. The last one occurred in Sept 2002. Was there a cold snap around then?
This animation shows what has been happening at the 10Hpa level over the last month:
This is likely to cause a big wobble in the antarctic polar vortex which may get very wavy around the edges, dragging very cold antarctic air towards the mid latitudes. Downward forces can bring icy blasts as these events buiold, this may have alrady been affecting South America.
What causes these events in the stratosphere? No-one really knows. Some think it has to do with the 'quasi bi-annual oscillation (QBO), some point to Rossby waves in the atmosphere. I'm wondering if it may be connected to the collapse of the thermosphere by 30% of it's volume caused by the long solar minimum, and the spacequakes caused by solar wind variation which can cause sudden releases of energy high above our heads equivalent to Richter scale 6-7 earthquakes. These happen up to five times a day. Maybe when we have better data, we will be able to see if periodicities in these these build up resonances which effect large scale atmospheric events.
A rather cool interpretational simulation movie from NASA:
I'd be grateful if antipodean BPLers would keep us posted over the next couple of weeks on the ups and downs of temperature there.