Heat waves: what you need to know; California opens cooling centers for vulnerable

A blistering heat wave is baking the western United States, the latest to blast the northern hemisphere in a summer that has brought extreme temperatures across Europe, Asia and North America.

Climatologists say the kiln-like conditions in California, Nevada and Arizona are caused by a heat dome -- a huge bubble of stationary high pressure that is trapping ever-hotter air.

And, they say, human-caused climate change is making these oppressive heat waves worse -- hotter, longer and more frequent.

Here's what you need to know about heat waves.

- What is a heat wave? -

Anyone suffering through sultry nights and sweltering days knows they're in a heat wave, but there are a few technical definitions.

The one the US government chooses is: at least two consecutive days when the minimum temperature for the area is hotter than 85 percent of July and August days in the same area, based on historical averages.

That minimum usually comes at night, which is important -- after a very hot day, our bodies tend to cool off at night. But if the temperature remains elevated, that's much harder. This is when people get ill.

It's also important to localize the definition. People accustomed to 85 Fahrenheit (29 Celsius) days are likely not fazed by 90 degrees. But if you live in a chilly, damp spot and the mercury hits 90, you'll find it much harder to cope.

- What causes heat waves? -

Generally it's an area of high pressure that parks itself in one spot, forming a heat dome -- imagine a huge greenhouse that lets in the sun's heat, but won't let any air flow through.

The high pressure prevents clouds from forming as it pushes air downwards, compressing and heating the air -- think of how a tire gets hot as you pump more air in.

Jet streams -- air that flows high in the Earth's atmosphere -- usually move pressure systems around the planet.

But they can meander. As the waves of a jet stream widen, they slow and can even stop. This is what leaves a ridge of high pressure in one place.

- Are heat waves dangerous? -

Yes, very. More people die from the heat every year in the United States than from any other extreme weather, including floods, tornadoes, and cold snaps, according to government figures.

A ferocious heat wave in Spain and Portugal in July left more than 1,700 people dead.

And hundreds died last year when a heat wave frazzled Canada and the western US, with temperatures of up to 121F (49C).

When it's very hot, our bodies find it more difficult to keep cool, which can result in a "cascade of illnesses," according to the World Health Organization.

These include heat cramps, heat exhaustion, heatstroke, and hyperthermia.

"Deaths and hospitalizations from heat can occur extremely rapidly (same day), or have a lagged effect (several days later) and result in accelerating death or illness in the already frail," the WHO says.

That means anyone who already suffers from problems with their heart or respiratory system is particularly at risk.

The effects of intense heat are not evenly felt across societies, and tend to be more acute in poorer, and more marginalized communities.

Homeless people or those who work outside during the heat of the day are obviously at risk, but so are people living in neighborhoods without tree cover, or near to sources of pollution like roads.

- What is climate change doing? -

Like all weather phenomena, climate change is super-charging heat waves.

Human activity, specifically the burning of fossil fuels, has warmed the Earth by an average of around 1.9F (1.2C) since pre-industrial times. Much of this warming has happened in the last 50 years.

US government data shows heat waves worsening in concert with a warming planet: Every decade since the 1960s they have got longer, hotter and more frequent.

"Their frequency has increased steadily, from an average of two heat waves per year during the 1960s to six per year during the 2010s and 2020s," the Environmental Protection Agency says.

"In recent years, the average heat wave in major US urban areas has been about four days long. This is about a day longer than the average heat wave in the 1960s."

A study after last year's record-breaking heat wave in Canada found it would have been "virtually impossible" without human-caused climate change.

The World Weather Attribution group said that global warming, caused by greenhouse gas emissions, made the heat wave at least 150 times more likely to happen.

California opens cooling centers for heat wave vulnerable
Los Angeles (AFP) Sept 3, 2022 - It is too hot in Nelly Amaya's place when the mercury surges into triple digits, driven by the punishing heat wave gripping the western United States.

"We don't have air conditioning at our house, we only have a fan," Amaya, a retiree, told AFP.

"We come here because we can't stay at home."

Amaya is one of hundreds of people in Los Angeles who are making use of the 40 cooling centers set up by the county's emergency department as a fearsome heat dome sends temperatures soaring.

The centers have been established in libraries, recreation and park facilities, and senior living facilities, offering shelter in air-conditioned rooms and cold drinks during the heat of the day.

Forecasters have issued an excessive heat warning for most of California, as well as parts of Nevada and Arizona, with thermometers logging highs over 110 Fahrenheit (43 Celsius) in some places.

The oppressive heat is expected to last well into next week, smothering a holiday weekend, with little relief in the way of cooler nights.

Doctors say when temperatures remain elevated for long periods -- particularly overnight -- it puts strains on the human body that can cause a cascade of illness, sometimes even leading to death.

Joseph Riser of the Los Angeles emergency management department said the city was doing its best to look out for those in need of help when the mercury rises over 100 Fahrenheit.

"Once that hits that peak... then the plans we have for adverse weather kick in and we begin rallying the troops, getting the supplies, making sure which centers can be open and that we have enough," he said.

- 'Stay hydrated' -

The effects of intense heat are not evenly felt across societies, and tend to be more acute in poorer and more marginalized communities.

Homeless people or those who work outside during the heat of the day are obviously at risk, but so are people living in neighborhoods without tree cover, or near to sources of pollution like roads.

"It may be people who are living in homes where there's no air conditioning, and maybe people who are unhoused," Riser said.

"It may be just young people seeking shelter from the heat, from maybe a home where the air conditioning doesn't work very well."

For Ruth Rivera, the Lafayette Park center near downtown Los Angeles is a godsend.

"It helps a lot, we have to stay hydrated, because it's really hot outside," she said.

The operator of California's creaking electricity grid on Friday called a third consecutive "Flex Alert," asking households to conserve power and turn up their thermostats to help reduce power demand.

"Reducing energy use during a Flex Alert can help stabilize the power grid during tight supply conditions and prevent further emergency measures, including rotating power outages," California Independent Service Operator said.

The heat dome is expected to last well into next week, with thermometers set to peak at 116 degrees Fahrenheit in some densely populated areas around Los Angeles over the upcoming Labor Day holiday weekend.

It is not unusual for southern California to experience heat waves in September, but temperatures above 100 degrees Fahrenheit are considered hot even for a place almost perpetually baked by sunshine.

Scientists say global warming, which is being driven chiefly by the unchecked burning of fossil fuels, is making natural weather variations more extreme.

Heat waves are getting hotter and more intense, while storms are getting wetter and, in many cases, more dangerous.

Related Links
Weather News at TerraDaily.com

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'Dangerous' heat wave hits southwestern US
Los Angeles (AFP) Aug 30, 2022
A "dangerous" heat wave was taking hold of the southwestern United States Tuesday, with punishing temperatures expected for the next week. Forecasters said the mercury could reach as high as 112 Fahrenheit (44 Celsius) in the densely populated Los Angeles suburbs as a heat dome settles in over parts of California, Nevada and Arizona. "Dangerously hot conditions expected through the week," the National Weather Service warned. "A prolonged period of excessive heat will significantly increase t ... read more