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    Explained: What is a heat dome and why is it so hot in US, Canada

    Explained: What is a heat dome and why is it so hot in US, Canada

    Explained: What is a heat dome and why is it so hot in US, Canada
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    By CNBCTV18.com  IST (Updated)


    Heat domes can also wreak havoc on agriculture as most crops are unable to cope with such extreme heat. This can lead to short-term food shortages and long-term increases in food prices.

    Canada and parts of the US have been struggling with a record-shattering jump in temperatures over the last week. While Lytton, British Columbia sizzled at 49.6°C (121°F) in Canada on June 29, cities of Portland and Oregon saw blazing high temperatures of 47°C (116°F) and 38°C (100°F), respectively.
    Hundreds have died due to extreme heat during this period, according to official data.
    The "heat dome" broke an 84-year-old record when two towns in Saskatchewan -- Yellow Grass and Midale – sizzled at 45°C (113°F) in July 1937, as per officials from Lytton climate station.
    Homes in one of the coldest countries in the world are built to fight harsh winter and keep the inhabitants warm. Lack of air conditioning is making matters worse for them.
    Lisa Lapointe, British Columbia’s Chief coroner, had said that there were at least 486 cases of “sudden and unexpected deaths”, an increase of 195 percent until June 30. The US state of Oregon also reported 60 deaths related to the increasing temperatures in the same period.
    What is a heat dome?
    According to the US National Ocean and Atmospheric Administration, “a heat dome occurs when the atmosphere traps hot ocean air like a lid or cap.”
    Daniel Swain, a climate scientist at UCLA’s Institute of the Environment and Sustainability, explains, a heat dome "is really just sort of a colloquial term for a persistent and/or strong high-pressure system that occurs during the warm season, with the end result being a lot of heat."
    The event is caused when hot air, created by a temperature gradient over the Pacific Ocean, rises high up into the atmosphere and gets carried towards the Northwestern North American landmass.
    Upon reaching there, strong jet streams trap the air and force it towards the ground level. The already hot air gets compressed and heats up further by the time it descends down, creating a self-sustaining high-pressure system.
    Winds that can disperse the hot air, turning the system into a heatwave, are instead swept down in the high-pressure system. The same system also inhibits the formation of any clouds, which would disperse some of the pressure, since there is no vertical motion of air currents.
    As the dome traps heat, it also exhausts natural heat sink mechanisms like evaporation by drying out most of the moisture in the land. This further fuels the ‘heat dome’ as more of the solar energy is used in fueling it.
    "So after a certain point, once it's been hot enough for long, it becomes even easier to get even hotter," added Swain. "And so that's why these things can often be really persistent because once they've been around for a little while, they start to feed off of themselves."
    How long does it take to dissipate?
    The conditions of the 'heat wave' generally last for a week or two, as the high-pressure system slowly moves further inland, where it finds more heatsinks and loses its source of hot air from the ocean. The large pressure system collapses on itself as it is unable to sustain or fuel itself any longer.
    David Phillips, a senior climatologist at Environment and Climate Change Canada, a government agency, said that the ‘heat dome’ weakened as it moved east but was still intense enough to significantly raise temperatures over the areas it was moving over.
    What are the long-term effects of a heat dome? 
    Heat domes can cause a cavalcade of effects even after they have dissipated. The super-hot conditions evaporate any moisture from the underbrush and create dry regions where wildfires can start and spread much more easily.
    The persistent conditions can also cause drought or drought-like conditions by evaporating a large amount of water while simultaneously increasing the demand for water for cooling purposes.
    Heat domes can also wreak havoc on agriculture as most crops are unable to cope with such extreme heat. This can lead to short-term food shortages and long-term increases in food prices.
    What can be done to prevent heat domes?
    The current ‘heat dome’ event is neither the first nor the last. A previous heat dome event occurred less than a year ago, in the middle of the COVID-19 pandemic.
    While heat domes are a natural phenomenon, their intensity, rate of occurrence, and frequency are all exacerbated by the global rise in temperature. As the Pacific Ocean continues to grow warmer, which itself will lead to a heating of the world in a vicious cycle, the temperature gradient across the ocean also increases. It is this gradient that causes more frequent, and intense, heat dome events to occur.
    Zeke Hausfather, a scientist at Berkeley Earth, a climate data non-profit, said the Pacific north-west had warmed by nearly 1.7°C (3°F) in the last 50 years.
    John Horgan, British Columbia’s Premier, said, "This is not a British Columbia problem, it's not a Canada problem, it is a global challenge.”
    Canadian Prime Minister Justin Trudeau expressed similar sentiments. "We've been seeing more and more of this type of extreme weather event in the past years. So realistically, we know that this heatwave won't be the last,” he said.
    Jay Inslee, Washington’s State Governor, told MSNBC, "This is the beginning of a permanent emergency."
    "We have to tackle the source of this problem, which is climate change," Inslee added.
    US President Joe Biden added that climate change was the core reason behind the "dangerous confluence of extreme heat and prolonged drought."
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