It's Hot Up Here, Eh?

Just in case you haven’t noticed, it’s been a bit hot in Canada.  Also in north western USA.

Apparently it’s all due to a “heat dome” and these are not new (for example the link there explaining what one is is from 2020).  Fundamentally it’s just a high pressure system that doesn’t move away, getting trapped in place by other weather systems around and heats up a location with no relief from a following cold front (that inevitably always comes).  High pressure systems do two things that increase the temperature in an affected area:

·  they take air from higher altitudes (which is initially at a lower pressure) and compresses it, which warms it up – you might notice that when you release a gas from compression it gets cold, which is how your air-conditioner and fridge work, and

·  they dampen wind that could otherwise bring in cooler air from other areas.

This is what North America looked like at 2200 UTC on 29 June of this year (with my addition of high and low pressure system markers and an x to indicate where Lytton is):

The white streaks indicate wind (and its direction by increasing width of the line).  There was basically no movement of air along the west coast and inland which meant that the air that was there was just baking in the clear, cloudless skies (which is another feature of the high pressure system).

Could this situation have occurred without climate change?  Maybe.  Could it have got quite so hot?  It’s unclear.  It’s basically impossible to say that any single event is a consequence of climate change, all we can do is look at the trends.  The question we need to ask is whether these heat domes are moving northwards, as a trend.  Unfortunately, that is hard to tell too, since the term only entered into public consciousness in 2011, as far as I can tell.  At that time, the heat down was a lot further south, but the sample isn’t large enough to tell.

All I can suggest is that, if you are interested in what is going on, and why, it’s probably better to visit a site that is interested in weather and climatology rather than one that is interested in denying climate change.  Even if the events in Canada can’t be definitively pinned on climate change.