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<\/div>High temperatures hit Joshua Tree, California, on 5 June 2024<\/p>\n
Gina Ferazzi\/Los Angeles Times via Getty Images<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
Mexico has been experiencing a severe heatwave<\/a> due to a massive heat dome that has been affecting the country for weeks. Now this system has extended northwards into the southern US, causing extreme temperatures across a large region.<\/p>\n A heat dome is not a clearly defined scientific term, but it is used by many weather forecasters. The American Meteorological Society defines it<\/a> as an \u201cexceptionally hot air mass that develops when high pressure aloft prevents warm air below from rising\u201d. High pressure results in clear skies because sinking air warms as it descends \u2013 clouds form under the opposite circumnstances, with water droplets condensing out as rising air cools<\/span>.<\/p>\n These high-pressure conditions mean lots of sunshine, which results in further warming and can dry out the soil, leading to less evaporation and a reduced chance of clouds and rain. These positive feedbacks can produce hotter and hotter conditions the longer the heat dome stays in one place. While heat domes cause heatwaves<\/a>, there can be heatwaves without heat domes.<\/p>\n <\/p>\n The jet streams are fast-flowing bands of wind<\/a> in the upper atmosphere that usually help move weather systems along the planet\u2019s surface. But sometimes big loops form in a jet stream, resulting in weather systems getting stuck<\/a> in the loops. These blocking patterns, as they are known, can lead to extreme cold, extreme rain or, in the case of heat domes, extreme heat<\/a>.<\/p>\n During the 2021 heat dome, several North American cities broke temperature records<\/p>\n Joshua Stevens\/NASA Earth Observatory<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n They can last anywhere from days to weeks. For instance, an extreme heat dome<\/a> over Canada and the northwest US in 2021 lasted nearly a month. During this event, the temperature reached nearly 50\u00b0C (122\u00b0F) in British Columbia, the highest ever recorded in Canada.<\/p>\n Heatwaves in general are becoming more frequent<\/a> because of climate change, but most studies don\u2019t look specifically at heatwaves caused by heat domes. There is a lot of debate about how warming will affect the blocking patterns that trap heat domes<\/a> in place. A 2023 study<\/a> concluded there will be an increase in \u201csummer heat-dome-like stationary waves\u201d over northwestern North America.<\/p>\n Yes, this is certain. Because the world is now nearly 1.5\u00b0C warmer than in preindustrial times, when heat domes form today surface temperatures can get hotter than they previously would have. For instance, one study concluded<\/a>\u00a0the extreme temperatures recorded during the 2021 heat dome in Canada were \u201cvirtually impossible without human-caused climate change\u201d. There is also some evidence that the intensity of heat domes is outpacing the warming trend, suggesting climate change is amplifying their intensity<\/span>. \u201cThe intensities of hot extremes associated with\u2026 heat dome-like atmospheric circulations increase faster than background global warming in both historical change and future projection\u201d, states a 2023 study<\/a>.<\/p>\n Topics:<\/p>\n<\/section><\/div>\nWhat is a heat dome?<\/h2>\n
What makes high-pressure systems get stuck?<\/h2>\n
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<\/div>How long do heat domes last?<\/h2>\n
Are heat domes becoming more common as a result of global warming?<\/h2>\n
Are heat domes becoming hotter as a result of global warming?<\/h2>\n