People who suffer from seasonal allergies are attacked by a higher amount of pollen during a longer season due to rising temperatures.
Global warming is also triggering worrying cases of extreme allergies, experts warn.
People could see the storm, but not what was in it.
Trillions of pollen particles, sucked into the clouds as the storm formed, were now being torn into even smaller fragments by rain, lightning, and humidity.
They were then thrown back to Earth for people to inhale.
It was around 18:00 PM on November 21, 2016 when the air in Melbourne, Australia, became deadly.
Emergency phone lines were boiling, people unable to breathe were flooding hospitals, and the demand for ambulances was so great that the vehicles could not reach people stuck at home.
In the emergency rooms there were eight times more people with breathing problems than expected.
Almost 10 times more people with asthma were admitted to hospital, and ten of them died.
Among them 20-year-old student rights who passed out on her own lawn, waiting for an ambulance while her family tried to revive her.
One survivor described how he was breathing normally, and then, within 30 minutes, he could no longer get air.
"It was crazy," He said to journalists from a hospital bed.
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Paul Beggs, an environmental health scientist and professor at Macquarie University in Sydney, Australia, remembers the incident well.
"It was an absolutely massive event. Unprecedented. Catastrophic."
"People in Melbourne, doctors, nurses and people in pharmacies didn't know what was going on," he recalled.
It soon became clear that a massive case of "storm asthma," which occurs when certain types of storms break up pollen particles in the air, releasing proteins and showering them on the unsuspecting people below.
Widespread proteins can trigger allergic reactions in some people, even those who were not previously asthmatic.
"Asthma storm" events like the one that hit Melbourne are an extreme example of how pollen from plants, and the allergies it causes, are changing dramatically due to climate change.
As temperatures rise, many areas, especially the United States, Evropa and Australia, are experiencing seasonal allergies affecting an increasing percentage of people, over a longer season and with worse symptoms, scientists say.
It is estimated that by 2025, pollen levels in America will be higher than historical average in 39 states.
It will likely only get worse in the years to come, scientists warn.
Pollen itself is a crucial and ubiquitous component of our world.
These microscopic particles are transferred from plant to plant, allowing them to reproduce.
While some plants spread pollen with the help of insects, others rely on the wind, sending huge amounts of this powdery substance into the air.
Many species of trees, grasses, and weeds depend on wind dispersal to obtain pollen.
They are particularly prone to causing seasonal allergies or hay fever.
This happens when your immune system mistakenly identifies pollen as a harmful substance, triggering a reaction normally reserved for pathogenic bacteria or viruses.
Common symptoms may include a runny nose, itchy eyes, and sneezing.
In some cases, seasonal allergies can cause breathing difficulties when inflammation of the airways causes swelling, making it difficult for enough air to enter the lungs.
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Melbourne was unfortunate epicenter of storm asthma, with seven mass asthma storm events recorded since 1984, but similar incidents have occurred all over the world, from Birmingham in Great Britain to Atlas in the USA.
Although these are still rare events, climate change may increase the likelihood of storm asthma incidents, partly because it lengthens pollen seasons, but also because it encourages frequency of extreme weather events, including a storm.
It's impossible to determine exactly how much climate change contributed to the 2016 Melbourne storm asthma incident, but Paul Beggs is "pretty sure" it had some influence.
"We know that climate change is causing to a higher amount of pollen in the atmosphere.
"They change the seasonal nature of pollen and the types of pollen we are exposed to," he explains.
Beggs, who has extensively researched stormy asthma, published a 2024 study in which he explored the links between this phenomenon and climate change.
How storms drastically increase the strength of pollen
Exactly how storms trigger or worsen asthma in this way is not yet fully understood.
The leading theory is that cold downdrafts that occur during storm systems generate strong crosswinds that blow across the land surface, raising pollen grains and fungal spores from grass and plants.
They are then carried high into the storm by updrafts, where the moisture in the clouds causes them to swell and break into smaller fragments, massively increasing the number of allergen particles in the air.
The strong electric field generated during storms can also enhance pollen fragmentation.
This smaller particle size makes it easier for pollen fragments to enter the respiratory tract because they are brought down to the surface of the earth by cold downward air currents.
Pollen levels seem to be jumping. during the first 20-30 minutes of the storm, according to studies of this phenomenon.
It seems that especially affects younger people.
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Mass events of storm asthma are still very rare.
But climate change is increasing people's risk of pollen exposure in other ways as well.
Rising temperatures mean that pollen seasons (when plants release pollen, usually during spring and summer) are starting earlier and lasting longer, says Elaine Fuertes of the National Heart and Lung Institute at Imperial College London.
"There will be people who will have symptoms earlier in the year, for longer periods of time," the scientist says.
In parts of the world, including the US and Europe, one of the key culprits is ragweed – a widespread group of flowering plants that many consider a weed.
There are many different types of ragweed around the world, but they can produce incredible amounts of pollen.
A single plant can release about a billion pollen grains, for example.
Ragweed grows in gardens and on farms, but also in various corners of the urban landscape.
Ragweed pollen allergies are already affecting some 50 million people in America alone.
A study that analyzed data from 11 locations in North America between 1995 and 2015 found that ten of them had longer ragweed pollen seasons, sometimes much longer.
During that two-decade period, the season was extended by 25 days in Winnipeg, Manitoba, 21 days in Fargo, North Dakota, and 18 days in Minneapolis, Minnesota.
"Winter is warmer, spring is coming earlier, and fall is coming later, so the amount of time you spend outside in contact with allergen pollen is definitely increasing," says Luis Ziska, assistant professor of environmental health sciences at Columbia University in New York, USA.
These changes are becoming more drastic in northern parts of North America, Europe and Asia, says Ziska, who has researched ragweed pollen season.
But these changes are also being observed in Australia and the southern parts of South America and Africa.
Without urgent reductions in greenhouse gas emissions, the consequences are likely to only worsen.
One study from 2022 estimated that, by the end of the 21st century, the pollen season will start up to 40 days earlier.
It will end 15 days later than it does now, potentially meaning two more months of symptoms per year for people who suffer from hay fever.
It's not just humans who are exposed to allergens for longer periods of time.
And the amount of allergens in the air is increasing in many parts of the world.
The pollen season in the continental United States began three days earlier in the 2000s than during the previous decade, but the amount of pollen also in the air was 46 percent higher.
In part because carbon dioxide (CO2) levels in the atmosphere are rising due to emissions from human activities.
Many of the most problematic plants for people who suffer from hay fever thrive on CO2.
Researchers have grown a certain type of grass under a different level of CO2.
They found that plants grown in an atmosphere containing 2 parts per million (ppm) of CO800 had flowers that produced about 50 percent more pollen than plants grown in air that contained half as much carbon dioxide.
The latter mimics current levels of CO2 in the Earth's atmosphere.
Some scientists have experimented with growing different types of oak trees, whose pollen often causes hay fever in countries such as South Korea.
Under a 720ppm CO2 scenario, they found that every oak tree contained an average amount of pollen 13 times greater than what the trees had under the 400ppm scenario.
Even at 560ppm, pollen production was 3,5 times higher than current levels.
Ziska, author of the book Greenhouse planet published in 2022, he conducted similar experiments with ragweed.
His results mirror those of other researchers.
"Every time we increased the carbon dioxide, the ragweed would react and release and produce more pollen," he says.
"There's also been evidence that it produces more allergenic forms of pollen, which can cause your immune system to react even more intensely than before," he explains.
The spread of invasive species to new parts of the world is also causing allergic reactions among new generations.
Ragweed is native to North America, but spread throughout Europe, as well as in Australia, Asia and South America.
Already some 60 percent of people in Hungary, 20 in Denmark and 15 in the Netherlands They are supposedly sensitive to pollen. this productive group of plants.
It is particularly worrying that it is estimated that to 2050. The concentration of ragweed pollen in the air will be about four times higher compared to today.
Even in parts of Europe where ragweed pollen is now almost non-existent, such as southern Great Britain and Germany, "pollen contingents become sizeable" under moderate or worst-case climate scenarios, the authors of a 2015 study warned.
They suggest that the continued spread of invasive species is responsible for about one-third of the increase.
The remaining two-thirds are specifically caused by climate change, including the lengthening of the growing season as temperatures increase.
"The season will arrive earlier, be longer and more intense for those who experience allergy symptoms."
"Then there's the greater risk of new susceptibility for previously unexposed populations," Fuertes says.
Not every region in the world will experience increased pollen production.
Some researchers have argued that Southern California, for example, will experience earlier but less productive pollen seasons, mainly as result of reduced precipitation.
But these predictions do not count all the potential consequences of climate change on airborne allergens.
There could be health consequences caused by the increased likelihood of forest fires because it increases the risk of both asthma and allergy symptoms.
The amount of pollen in the air still varies from year to year, Fuertes points out.
This is not very helpful for people who suffer from hay fever.
"Once you become sensitized and develop allergy symptoms, you're likely to continue to experience them during years when pollen levels are lower than average," she says.
"You'll react to whatever pollen is there," he explains.
So what can people do about this?
Reducing carbon emissions would help prevent some of the worst climate impacts, and other strategies could also mitigate the problem.
It is also possible to take some drastic, but direct, interventions.
Some American cities even established ragweed control commissions a century ago.
"Chicago hires 1.350 people to fight hay fever," is one of the newspaper headlines from 1932.
People, otherwise unemployed during the Great Depression, were paid the equivalent of a week's worth of food and lodging (and "25 cents in cash") for each day spent clearing the plant, media reported.
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Although this might sound innocuous to you, a difference has been noticed.
A 1956 study by New York's Operation Ambrosia estimated that mass cutting of this plant reduced pollen production by about 50 percent.
Such an action is being carried out in Europe today.
In Berlin, workers have been sent to find and eliminate ragweed throughout the city, while Switzerland has banned the import or sale of the plant in 2024 and has set up volunteer groups to patrol public parks to uproot it.
Other solutions lie in smarter urban design.
"We definitely need to green our cities, but in a thoughtful way," says Fuertes.
Planting exotic species can trigger new allergies.
Opting for male trees that produce pollen over "messy" female trees that produce fruit and seeds - so-called "botanical sexism" - can also increase pollen levels in urban areas.
But studies have shown that the consequences of this bias are relatively small in large cities like New York.
Scientists warn that it is also important to monitor and predict pollen levels.
"We need to know what we're breathing in. It's a pretty fundamental thing when it comes to our health," says Paul Beggs.
He points out that most people take for granted the ability to get reliable and verified real-time information about metrics like temperature or precipitation in their area.
Relatively few can say the same about airborne allergens.
But even those services that model pollen measurements in a comprehensive, detailed way, such as the Finnish Meteorological Institute, do not monitor or model airborne allergen levels, which are more accurate.
Each pollen particle can release different amounts of allergens and it depends on weather conditions.
There are different metrics, Fuertes points out, and the ones she showed are more closely related to allergy symptoms.
"Nobody routinely measures allergen levels, and we should be working on that," Fuertes says.
The scientific data is clear, experts say.
Without concrete, coordinated action, climate change will continue to worsen hay fever in many areas of the world.
This could include more dramatic, deadly events such as storm asthma.
But it could also mean more people sniffling and suffering, over a longer season, every year.
"We now have studies showing that it really does have an impact on human health, and there will be more of that," Beggs warns.
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