Circulating Knowledge of
By U. S. National Weather Service/National Ocean Service - https://www.weather.gov/jetstream/hi and https://aambpublicoceanservice.blob.core.windows.net/oceanserviceprod/facts/heatdome.jpg, Public Domain, Link
Starting with the gradual impact, global climate change has been warming the oceans for some time. The western Pacific ocean, in particular, is warming at a considerable rate where surface winds and currents push that heat to the east. So we have a warmer-than-normal Pacific ocean surface temperature, but this doesn't really add up to a heat wave. That's where 2 other weather events come into play as catalysts.
In mid-to-late June of 2021, there were 2 meteorological events happening in different parts of the globe. In China, there were torrential rains hitting the country that resulted in a higher-than-average atmospheric temperature. This heat was sucked into the jet stream, or a system of atmospheric air currents, which started moving that heat to the east over the Pacific ocean. As it traveled, this created a patch of the atmosphere with unusually high pressure.
The 2021 Western North America Heat Dome traveled all the way to the eastern reaches of Canada before dissipating, lasting about 2 weeks!
The heat dome that hit North America in 2021 is recorded as a "1000 year event made 150 times more likely by global climate change"
Convection & Efficient Heat Transfer
That isn't to say that these meteorological events meeting played a magic trick either. A heat dome is born of trapped heat. Thanks to the growing warmth of the ocean surface temperature, tropical storms were unable to dissipate the high-pressure zone generated from the heat transferred by the jet stream. And thanks to the heat from the southwestern US drought, we saw the formation of the "bottom" of a high pressure container. Having a high-pressure surface covered by a high-pressure "lid" traps circulating air until it is disrupted by a source of cool air. In the case of the heat wave above, there were 2 spots where cool air was introduced: the Hudson Bay and the Atlantic ocean. The former dropped the intensity of the heat dome as the westerly winds moved it eastward, but it didn't dissipate until the eastern part of the dome reached the Atlantic ocean in mid-July.
Okay, so we have a lot of trapped heat in a dome, why does this result in such an intense wave of extreme heat?
Enter the convection oven which introduces an unlikely ally to the mix: a fan. One would think this would interfere with the heat being generated from the oven, but the contrary is true. Similar to the jet stream in our heat wave example, this circulating air is now carrying the warm air. Since the oven is creating a vacuum from outside elements, this added wind simply adds more force behind the circulating heat, both increasing the speed at which the contents are cooked and, in turn, reducing the net energy required to do the same work as a conventional oven.
In the case of the western North America heat wave, the heat dome is the oven, and all of us inside it are being cooked. At least it's being efficient! Similar to how an oven creates a vacuum from outside elements, the high-pressure containerization of the heat dome creates a cavity for the heat to circulate without drastic cooling. Heat domes are essentially the Earth's mobile convection oven in action.
Heat domes sustain themselves using convection, the same principle used in convection ovens to heat food faster and more efficiently, only we're in the oven with heat domes!
By U. S. National Weather Service/National Ocean Service - Link
The prolonged conditions in recent heat waves has been enough to cripple human-built infrastructure causing railroads to warp, roads to shatter, and power lines to sag
In addition to the physical reality of prolonged exposure to extreme heat, humans also have a few other dimensions to consider, one of them being the infrastructure we've built and rely on. A lot, and I mean a LOT, of human infrastructure in the northern hemisphere is not built with extreme heat in mind. From cabling to roads to transport, all of these buckle under the pressure of extreme heat. We saw this with the above heat wave where reports of deformed railroad tracks, sagging power lines, and the shattering of concrete roads and sidewalks due to thermal expansion were widespread. Under these days of prolonged exposure to extreme heat, it shows that human infrastructure begins to crumble rather quickly, something that is abundantly clear now, but needs attention much sooner rather than later.
In a similar light, when our infrastructure fails, we also see our social dimension begin to deteriorate as well. Humans are able to act within our society thanks to a lot of this infrastructure, and when it's down for the count or destabilized, our ability to live and work is diminished or otherwise endangered. During this heat wave, a lot of businesses closed down due to this infrastructure being down, and those that forced people to work in the extreme conditions were faced with walkouts and strikes. Turns out people don't want to risk their lives on their employer's behalf.