Sunny and Warm! – But Why? The Answer lies to the North.

The forecast is so easy.  Sun. It’s going to be sunny and warm all the way into the weekend.  We will be close to record highs at the Airport as well. Our record for today is 22ºC. That’s not out of the question today or tomorrow.  (That means there’s no excuse not to vote 🙂 either Tuesday at City Hall or Main Voting Day Saturday Oct 20 at the Athletic Hall. Bring two pieces of ID).

But what is the reason for this amazing period of sunny and warm weather? 

First, the immediate cause, a strong ridge of high pressure allowing warm air up from the south and pushing the jet stream into Yukon. The image below should be animated.  Watch the jet stream (the coloured bands of strong upper-atmosphere winds)

Watch as the jet stream loops over us. You can see how it bends and some pieces break off to form small lows, and then it straightens a little only to bend again into quite a wild pattern as the ridge of high pressure (the purple and white areas) gradually moves off to the east but is quickly replaced.

It is not uncommon for the jet stream to get ‘stuck’ in these kinds of very wavy patterns, and if we are stuck under or over one of those waves, then our weather gets ‘stuck’ in a specific mode as well.  In this case, clear and relatively warm skies.

The bigger question – Why is the jetstream like this? 

Have you noticed this pattern before? Do you remember any other times recently when we have seemed to have the same pattern of weather for days, even weeks on end?  You probably do. It happens often, and I believe it is happening more often than it used to.

If you have followed this blog closely in the past, you will likely remember me mentioning this phenomenon. If you haven’t here’s a primer.

A research scientists at Rutgers University in the USA named Jennifer Francis was one of the first to publish evidence and make the link between extreme weather, the wavy jet stream, and the rapid warming and melting of the Arctic.

She has now published 8 papers on the subject, between 2012 and 2015.

In the latest article from 2015 “Evidence linking rapid Arctic warming to mid-latitude weather patterns” she and Natasa Skific  say (a simpler description awaits below):

new metrics and evidence are presented that suggest disproportionate Arctic warming—and resulting weakening of the poleward temperature gradient—is causing the Northern Hemisphere circulation to assume a more meridional character (i.e. wavier), although not uniformly in space or by season, and that highly amplified jet-stream patterns are occurring more frequently. Further analysis based on self-organizing maps supports this finding. These changes in circulation are expected to lead to persistent weather patterns that are known to cause extreme weather events. As emissions of greenhouse gases continue unabated, therefore, the continued amplification of Arctic warming should favour an increased occurrence of extreme events caused by prolonged weather conditions.

A description using less technical language:  
We already know the Arctic is warming faster than the rest of the planet.

The difference in temperature, especially in the Fall and Winter, between the Arctic and mid-latitudes (like Canada, the USA, Europe) is shrinking.

The jet stream has been observed to be wavier more often than in the past due to that shrinking difference in temperature.

A wavy jet stream makes for stuck weather patterns (like we are seeing here today). Stuck weather patterns lead to extremes.

So we can expect that as CO2 and other greenhouse gas levels rise from fossil fuel use, the Arctic will continue to warm faster than elsewhere and so extreme weather patterns will continue.

So Ya. It’s Climate Change, it’s us, and we better do something about it.

So in the end, you, me, your neighbour, your friend, your grandma, your uncle… we all have contributed to making this sunny day.  On the surface, in the moment, it seems quite wonderful.  But that candy has a sour centre. You’ve likely seen the news lately with headlines like:

We have 12 years to limit climate change catastrophe, warns UN

But that’s just the Guardian… they like to get people worried right?  Alright, here’s the actual press release from October 8th from the UN IPCC.

“One of the key messages that comes out very strongly from this report is that we are alreadyseeing the consequences of 1°C of global warming through more extreme weather, rising sea levelsand diminishing Arctic sea ice, among other changes,” said Panmao Zhai, Co-Chair of IPCC Working Group I

Sound familiar?

More:

The decisions we make today are critical in ensuring a safe and sustainable world for everyone, both now and in the future, said Debra Roberts, Co-Chair of IPCC Working Group II.
“The next few years are probably the most important in our history”

“A safe world.” —- “The most important time in our history” —-

Remember that this is a press release that had to be agreed to by people representing dozens of countries all with competing interests and goals. Yet they all agreed that our safety is at stake. They all agreed that we have to act immediately.

“The good news is that some of the kinds of actions that would be needed to limit global warming to1.5oC are already underway around the world, but they would need to accelerate,” said ValerieMasson-Delmotte, Co-Chair of Working Group I.

We can do it, but we have to make big changes, very big changes, in a very short period of time.  I am willing to make and fight for those changes, are you?

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