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Allergy season will become increasingly brutal as climate warms

Pollen is a well-known airborne allergen that can cause allergic reactions varying from mild itchiness and sneezing right up to serious problems with breathing and anaphylaxis. It is estimated that as many as 60 million people in the USA suffer from seasonal allergies each year. And now, a study from scientists at the University of Michigan has suggested that the length and intensity of allergy season will increase dramatically as Earth’s climate warms.

“Pollen-induced respiratory allergies are getting worse with climate change,” said study first author Yingxiao Zhang. “Our findings can be a starting point for further investigations into the consequence of climate change on pollen and corresponding health effects.”

The scientists considered pollen from 15 different plant species that occur throughout the U.S. and modeled the potential responses of these plants to various climate change scenarios. They investigated the potential impact of increases in temperature and changes in precipitation on the different grasses, weeds and trees. 

The production of pollen by many plant species will be affected by a warming climate, which will enable them to start producing pollen earlier than normal and continue for longer. Hotter temperatures can also increase the amount of pollen produced, and even its allergenicity (capacity to cause an allergic reaction).

Initially, the researchers tested their predictive model using historical climate data and known pollen levels for the period 1995 through 2014. They then used their model to predict pollen emissions for the last two decades of the 21st century, under different potential warming conditions.

Their results predict that, by the end of this century, pollen emissions could begin 40 days earlier in the spring than was the case between 1995 and 2014. In addition, misery for allergy sufferers could last longer – an additional 19 days – before high pollen counts subside. This would be the case under the most extreme climate change scenario, but even under the best-case scenario, where global average temperatures rise by only 2.7oF (1.5oC), pollen season will still start 20 days earlier.

In addition, thanks to rising temperatures the emission of pollen could increase by 40 percent. If the model considers the effects of increasing CO2 levels as well, the annual amount of pollen emitted each year could increase by as much as 200 percent.

The experts from Michigan University say that pollen season in the U.S. has already moved earlier in the year over the past three decades. They found that between 1990 and 2018, the start of the pollen season shifted from around Valentine’s Day (14 February), to St Patrick’s Day (17 March) each year.

Pollen-induced respiratory allergy affects up to 30 percent of the world population, particularly children, and causes large economic losses in terms of medical expenses, missed work and school days, and early deaths.. In the U.S., pollen allergy is particularly difficult for the 25 million Americans with asthma, as it makes symptoms worse.

Allison Steiner, UM professor of climate and space sciences and engineering, said that while allergy suffering will increase across the U.S., the Southeast will get hit hardest. She said the pollen emissions modeling developed by her team could eventually allow for allergy season predictions targeted to different geographical regions. 

“We’re hoping to include our pollen emissions model within a national air quality forecasting system to provide improved and climate-sensitive forecasts to the public,” said Professor Steiner..

According to the researchers, this study provides an important predictive tool to start investigating the consequences of climate change on future plant communities and their corresponding health effects.

The study is published in the journal Nature Communications.

By Alison Bosman, Staff Writer

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