The world's hottest two days on record occurred in July, and 2024 is expected to be the hottest year on record. Heatwaves are becoming more frequent and more intense, often arriving earlier than expected. Factoring in humidity, extreme weather is already testing the limits of the human body. More than 1,300 people died during the Hajj pilgrimage in Saudi Arabia in June when temperatures reached about 52 degrees Celsius (126 degrees Fahrenheit), and heatstroke deaths have been recorded in the United States, Thailand, India, Mexico and other countries this year. In parts of Europe, where rising temperatures have caused more than 47,000 deaths in 2023, caution is needed against even more extreme weather this summer.
Why is extreme heat dangerous?
There are many reasons. High temperatures make people more susceptible to dehydration, increasing the risk of heart attacks and strokes. Heat can worsen respiratory problems, especially in places with high levels of air pollution. Heatstroke makes it harder to work and increases the chances of injury. It is difficult to know the exact number of people who die from heat each year, and most of them go uncounted. According to a study led by the Barcelona Institute for Global Health, heat-related deaths in Europe will reach 61,672 in 2022, but this figure may underestimate the actual total. Emerging countries are harder hit than developed countries because they tend to get little respite from the sun. Most people work outdoors, and few have effective air conditioning at home. Concrete and asphalt in urban areas trap heat and increase nighttime temperatures, contributing to heatstroke. Studies have found that women and the elderly are most susceptible to the effects of extreme heat.
How is extreme heat measured?
Weather forecasters are increasingly using heat stress and discomfort indices (such as humidity index, heat index, and perceived temperature) to understand the health risks posed by high temperatures. The “wet bulb temperature” is one such index, which takes into account the effect of humidity, which makes it harder for the human body to cool itself down by sweating. For example, if the temperature is 42°C and the humidity is 40% (think Phoenix, Arizona in July), the wet bulb temperature is about 30°C. If the temperature is lower but the humidity is high, at 80%, the wet bulb temperature is about 35°C. This is high enough to cause heatstroke in healthy people with unlimited shade and water, and is already starting to occur in subtropical coastal regions. In reality, shade and water are often limited, and heat can kill even at a much lower wet bulb temperature. A 2020 study published in Science magazine found that areas affected by the 2003 European and 2010 Russian heat waves that killed thousands had wet-bulb temperatures below 28°C.
How is wet bulb temperature measured?
Originally, this was done by wrapping a wet cloth around the bulb of a thermometer. Scientists recorded the temperature after the water evaporated, similar to how sweating cools the body. Today, wet bulb temperatures are measured using electronics at weather stations, and satellite data from NASA and the International Space Station are also being used to further study hotspots. The National Oceanic and Atmospheric Administration has also developed a tool to predict wet bulb globe temperature, a more advanced indicator of heat stress that takes into account wind speed, sun angle, and cloud cover.
What is the problem here?
Traditionally, South Asia and areas with subtropical climates experienced the highest heat and humidity. Some places in India saw wet bulb temperatures exceed 32 degrees, and the United Nations predicts that India will be one of the first countries to see a wet bulb temperature exceeding 35 degrees. According to the University of California, Berkeley, global warming and the El Niño phenomenon are likely to break temperature and humidity records this year across a wide range of areas straddling the equator, including Florida, Texas, much of Africa, India, Australia, and Central and South America. Even places that are usually warm are experiencing an increase in incredibly hot days. The UK recorded a record high temperature of 40.3 degrees in July 2022, but the wet bulb temperature remained around 25 degrees due to relatively low humidity. Barcelona experienced its hottest day on record in late July. According to the World Meteorological Organization, heatstroke warnings were issued for about half of the population in the United States on August 1. Japan, Greece, Hungary, and Croatia were among the countries that experienced their warmest July on record.
What are the economic impacts of heat?
In places with extreme heat, every aspect of life becomes more difficult, and inequality is especially acute in cities. But even cooler places feel the effects, typically in the form of higher food and energy prices. Coffee prices soared to a 45-year high this year as prolonged heat and drought worsened supply shortages in Vietnam, the world's largest producer of robusta coffee. Dry weather this year in Russia led analysts to cut wheat production forecasts. And supplies of crops like canola and chickpeas remain vulnerable to heatwaves. Previous El Niño events have had a pronounced impact on global inflation, boosting non-energy commodity prices by 3.9 percentage points and crude oil prices by 3.5 percentage points, according to a Bloomberg Economics model. Electricity consumption also rises during hot weather, and the price spike puts a strain on the power grid and consumers' wallets. Natural gas prices rose this summer as consumers worried about the risk of blackouts. Egypt, which normally exports natural gas, has turned to buying LNG as demand rises. The heat will worsen droughts, putting additional strain on hydroelectric and nuclear power plants. Extreme temperatures will increase the threat to outdoor activities, disrupting events such as concerts, religious gatherings and sporting events.
What does the heatwave have to do with climate change?
Attribution of extreme events, a new branch of science, has made some concrete connections between global warming and extreme weather. Heatwaves are most directly linked to human greenhouse gas pollution. And because heat, along with dryness and wind, fuels forest fires, scientists are now convinced that climate change is making wildfires worse in the western United States, Australia, and other regions. (The U.S. wildfire season is two months longer than it was in the 1970s and 1980s.) Global warming is increasing the intensity of tropical cyclones (also called hurricanes or typhoons). Warmer water and moist air, the result of global warming, provide more fuel for storms like the record-breaking Hurricane Beryl, which struck parts of the Caribbean and the United States in July. Extreme heatwaves are 30 times more likely to occur in India and Pakistan because of climate change.
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