Cause and Effect | There's a fundamental difference between the heatwaves in Europe and US
Both hemispheres have seen a spate of wildfires, heatwaves and flash floods. Though climate-crisis induced, these extreme weather events have different causes
Twenty one days into July, and the world has broken various temperature records.

It began with the average global temperature reaching 17.01°C on July 3, about 0.8°C higher than the averages recorded since 1979.
This record was broken on July 4, and then again on July 5, turning into the hottest first week of July ever, according to World Meteorological Organisation data, after the hottest ever June.
These temperatures have only turned more severe, with multiple severe heatwaves in both hemispheres, flash floods also in both hemispheres, and large swathes of land in both the US and Europe scorched from wildfires.

The reasons for these, while climate crisis induced, are all different.
First, the US.
The Western and Southern parts of the country were scorched by record-setting heat, the north-east was lashed with rain that triggered floods, and the Midwest was choked with wildfire smoke.
There were catastrophic floods in the Hudson Valley, an unrelenting heat dome over Phoenix, ocean temperatures hit 32.2°C off Miami's coast, a deluge in Vermont. Everything, but not yet everywhere, all at once.
While Phoenix in Arizona recorded a 19-day streak of temperatures of or above 43°C, Death Valley in California has had 84 consecutive days of 43.3°C. Death Valley, aptly named, has seen no reprieve even at night with 32°C for 47 nights.
“Death Valley at 1 am this morning was a mind-boggling 120°F (49°C), before bottoming out at 105°F (40.6°C) at 7 am. One of the hottest nights in Earth's recorded history," Colin McCarthy, a student of atmospheric science at UC Davis, said on Twitter.
The Valley fell just short of the new expected record of 55°C, which would have been the highest temperature recorded ever, globally. The previous temperature highs of 56.7°C in Death Valley and 55°C in Tunisia in July 1931 are both contested.
A digital thermometer at the Death Valley National Park hit 54.4°C at one point on Sunday, but it is not an official reading. The National Weather Service said the highest temperature recorded on Sunday was 53.5° C.

A sign board warning people to not walk in the area after 10am went unheeded, as the record setting heat inspired a sort of climate change tourism, a twisted form of eco-tourism, with people wanting to become a part of history by clicking selfies with the digital thermometer.
The heat wave has both long and short-term causes, said Arizona State University’s Randy Cerveny, who coordinates weather record verification for the World Meteorological Organization.
“The long-term is the continuation of increasing temperatures in recent decades due to human influence on climate, while the short-term cause is the persistence over the last few weeks of a very strong upper-level ridge of high pressure over the western United States,” he told Fortune.
This high pressure, a heat dome, has been around the southwest for weeks, and then moved to Phoenix.
According to scientists, a heat dome is triggered by a short change in ocean temperatures from west to east in the tropical Pacific Ocean during the preceding winter.
An El Nino has set in in the Pacific, with the temperature anomalies reaching the value of +0.9°C.
A heat dome occurs when an area of high pressure traps warm air over a region for an extended period of time. The longer that air remains trapped, the more the sun works to heat the air, producing warmer conditions. Picture a pressure cooker.
Heat domes generally stay for a few days but sometimes they can extend up to weeks.
The NOAA described it such: “...the western Pacific’s temperatures have risen over the past few decades as compared to the eastern Pacific, creating a strong temperature gradient, or pressure differences that drive wind, across the entire ocean in winter. In a process known as convection, the gradient causes more warm air, heated by the ocean surface, to rise over the western Pacific, and decreases convection over the central and eastern Pacific. As prevailing winds move the hot air east, the northern shifts of the jet stream trap the air and move it toward land, where it sinks, resulting in heat waves.”
The heat dome is forecast to extend into the weekend.
Now, Europe.

Large parts of southern Europe are in the grip of intense and dangerous heatwave conditions.
Temperatures reached the mid to high 30s last week. A temperature of 44.8°C was observed in Almeria, Spain last week. By the weekend, Greece recorded 41°C, Turkey 44°C and southern Germany 39°C. Authorities were forced to close the Acropolis during the hottest parts of the day amid health alerts; a large forest fire on La Palma, Spain, destroyed at least 4,500 ha of land forcing evacuations of over 4,000 people.
Meteorologists blamed it on Cerberus, and then Charon.
Cerberus is the hound of Hades guarding the Underworld. Charon is the ferryman of Hades, delivering souls to the Underworld.
No, scientists aren't turning to Greek myths to explain extreme weather. Only for the nomenclature.
Both Cerberus and Charon are anti-cyclones that have unleashed two back-to-back heatwaves on Europe.
An anti-cyclone is a large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counter clockwise in the Southern Hemisphere.
High pressure systems have small pressure gradients (the air pressure doesn't change rapidly). This means that the winds are gentle. As the air sinks, it warms up, leading to warm and dry weather.
While Cerberus started in the Sahara before moving across northern Africa and into the Mediterranean, Charon has entered Europe from north Africa.
"Italy, Spain, France, Germany and Poland are all facing a major heatwave with air temperatures expected to climb to 48°C on the islands of Sicily and Sardinia – potentially the hottest temperatures ever recorded in Europe," the European Space Agency said on July 13.
Land surface temperature is how hot the surface of Earth feels to the touch. Air temperature, what we see in daily weather forecasts, is a measure of how hot the air is above the ground.
The World Meteorological Organization said the extreme heat and rainfall was expected to extend into August.
The European Union’s Copernicus Climate Change Service, in its 2022 Global Climate Highlights, said that summer 2022 was the hottest on record for Europe, and 2021 was the second warmest year on record for Europe, while globally it was the fifth warmest.
According to a study recently published in Nature Medicine, more than 60,000 people died because of last year’s summer heatwaves across Europe. The mortality rate was highest in Italy, Greece, Spain and Portugal.
And it doesn’t end.

China’s Sanbao recorded 52.2°C over the weekend, smashing the old record by 1.7°C, after deadly heatwaves in eastern India last month.
“In many parts of the world, today is predicted to be the hottest day on record. And these records have already been broken a few times this year. Heatwaves put our health and lives at risk,” Tedros Adhanom Ghebreyesus, director-general of the World Health Organisation, tweeted on July 17.
“The Climate Crisis is not a warning. It’s happening. I urge world leaders to ACT now.”
While storms and heat domes aren’t a direct consequence of climate crisis as many deniers would point out, the warming of air and sea surface causes the pressure gradient making the weather phenomena more frequent and deadlier.
The trending headlines, popularised in the aftermath of the Covid pandemic, focus on the “new normal”. Data, however, shows that there is nothing normal about this altered reality.
Anything that is being normalised right now, will be shattered in a new record next summer, and then again the year after that.
All Access.
One Subscription.
Get 360° coverage—from daily headlines
to 100 year archives.



HT App & Website
