Heat wave
Temperatures that humans from a hotter climate consider normal can be regarded as a heat wave in a cooler area.
Heat waves have become more frequent, and more intense over land, across almost every area on Earth since the 1950s, the increase in frequency and duration being caused by climate change.
[14] In Greece, the Hellenic National Meteorological Service defines a heat wave as occurring over three consecutive days with temperatures at 39 °C (102 °F) or higher.
The Netherlands defines a heat wave as a period of at least five consecutive days in which the maximum temperature in De Bilt exceeds 25 °C (77 °F).
Heat storms occur when the temperature reaches 100 °F (37.8 °C) for three or more consecutive days over a wide area (tens of thousands of square miles).
In Canada, heat waves are defined using the daily maximum and minimum temperatures, and in most of the country, the humidex as well, exceeding a regional threshold for two or more days.
[22] The Australian Bureau of Meteorology defines a heat wave as three or more days of unusual maximum and minimum temperatures.
[24] Marine heatwaves have become a prominent subject of research in recent years, reflecting the fact that since the turn of this century many ocean areas have experienced peaks of temperatures, along with more frequent, more intense, more prolonged warming events than ever met on record.
[25] The genesis of marine heatwaves is mainly driven by a combination of oceanic and atmospheric factors, often triggered by high pressure systems that will reduce cloud cover and increase solar absorption by the sea surface.
Human-induced climate change appears bound to play a growing role in the development of marine heatwaves, with increasing impacts on marine ecosystems, such as mass mortality in benthic communities, coral bleaching events, disruptions in fishery catches, and shifts in species distributions.
[32][33] In the eastern regions of the United States a heat wave can occur when a high pressure system originating in the Gulf of Mexico becomes stationary just off the Atlantic Seaboard.
The southwest winds on the back side of the high continue to pump hot, humid Gulf air northeastwards.
The highest temperature recorded in South Africa (51.5 Celsius) occurred one summer during a berg wind along the Eastern Cape coastline.
[49] Health experts warn that "exposure to extreme heat increases the risk of death from cardiovascular, cerebrovascular, and respiratory conditions and all-cause mortality.
[56] Also more than 2,000 people died in Karachi, Pakistan in June 2015 due to a severe heat wave with temperatures as high as 49 °C (120 °F).
[60] When considering heat-related illnesses as well, actual death tolls from extreme heat may be six times higher than official figures.
[65] The heat index in the table above is a measure of how hot it feels when relative humidity is factored with the actual air temperature.
A study of countries in the United States found that the economic productivity of individual days declines by about 1.7 percent for each degree Celsius above 15 °C (59 °F).
[72] Calculations from 2022 suggest that heat waves will shrink the global economy by about 1 percent decrease by the middle of the 21st century.
They reduce labour productivity, disrupt agricultural and industrial processes and damage infrastructure that is not suitable for extreme heat.
[6][7] In 2016, a marine heatwave in Chile and its subsequent harmful algal bloom caused $800 million (USD) in export losses for the aquaculture industry as salmon and shellfish died off.
During the 2003 European heat wave, for instance, thousands of pigs, poultry, and rabbits died in the French regions of Brittany and Pays-de-la-Loire alone.
Feed supplementation with antioxidants like chromium can help address oxidative stress and prevent it from leading to other pathological conditions, but only in a limited way.
[87] For example, the record-breaking heat wave that afflicted Pakistan beginning in May 2022 led to glacier melt and moisture flow.
[88] Researchers have predicted that roughly 10-40% of all land vertebrate species will be affected by heat waves by 2099, depending on the amount of future greenhouse gas emissions.
[89] Heatwaves present an additional form of stress and evolutionary pressure for species that already deal with habitat loss and climate change.
[90][91] The species with sufficient genetic variation will be able to ensure some individuals can survive frequent days of high temperatures in the future.
[120] The heat wave occurred during the Indian dry season, which typically lasts from March to July with peak temperatures in April and May.
The study predicted that by the 2060s, annual heat wave-related mortality is expected to reach 29,000 to 38,000 in China, with a 28% to 37% increase in work hours lost.
[131] In the United States, the loss of human life in hot spells in summer exceeds that caused by all other weather events.
