As climate changes, pollen season may become longer and more intense, according to a study.

In the United States, allergy season could intensify as the climate gets warmer.

By the end of the century, pollen season could start up to 40 days earlier and last 19 days longer due to unchecked carbon emissions, according to a study published Tuesday in the journal Nature Communications. This would increase annual pollen emissions in the U.S. by as much as 40 percent.

Using climate models and pollen data, researchers predicted how and when plants and trees would release pollen in the future.

For the past 30 years, allergy seasons have been longer and more intense across all regions in the U.S.

According to William Anderegg, an associate professor of biology at the University of Utah, who was not involved with the new study, pollen seasons are starting earlier, lasting longer, and have about 20 percent more pollen in the air than they did in the 1990s.

According to Patrick Kinney, a professor of environmental health at Boston University School of Public Health, the new findings indicate that the current trends will persist in the future.

The increase in pollen could have serious consequences for individuals with allergies or asthma.

Asthma, a more serious condition, is the underlying cause of allergies, which are commonly associated with stuffy noses and itchy eyes. As time progresses, individuals with allergies may experience worsening symptoms and require more medication. Additionally, the prevalence of pollen allergies is likely to increase.

The climate-pollen connection

Yingxiao Zhang, a doctoral candidate in climate sciences at the University of Michigan and the study's lead author, states that both precipitation and the amount of carbon dioxide in the atmosphere affect the amount of pollen plants produce and emit. As a result, human-caused pollution could lead to a 250 percent increase in annual pollen emissions.

As climate change causes average temperatures to steadily rise, spring is starting earlier due to the increasing amounts of greenhouse gasses in the atmosphere.

While current data is limited, it's not sufficient to understand the impact of increased carbon dioxide on pollen. However, we do know that temperature affects pollen, and we're already observing this effect.

Zhang and her team employed two sets of data to develop their model. Initially, they utilized historical pollen data gathered from nearly 100 sites across North America to comprehend the correlation between pollen emissions and various drivers of climate change, such as temperature and atmospheric carbon dioxide levels. Subsequently, they integrated this data with information from 15 distinct climate models to construct a model that predicts future pollen seasons over the next 80 years as the climate evolves.

Using two hypothetical situations, they tested their model: one with no actions taken to decrease carbon emissions and another with moderate actions.

If the worst-case scenario occurs, average temperatures on the continent could increase by up to 6 degrees Celsius, which is equivalent to 11 degrees Fahrenheit. This would result in an extension of pollen season by approximately 30 days. On the other hand, in a moderate scenario where Earth warms by a maximum of 3 degrees Celsius, or 5.4 degrees Fahrenheit, the pollen season is predicted to lengthen by about 10 days.

The appearance of pollen changes varies across the U.S. based on the location and the surrounding plant and forest composition. Scientists have already observed significant changes in northern states.

In parts of northern Minnesota and North Dakota, ragweed season has increased by 21 days from 1995 to 2015, according to data from the Environmental Protection Agency. Similarly, ragweed season was six days longer in Oklahoma during the same period.

In the past, trees have been the most prominent during spring pollen season, followed by grass in late summer and ragweed in the fall. However, the new model suggests that these seasons will overlap in the summer due to warming temperatures causing some plants to bloom earlier or later.

Allergy sufferers could experience more misery if the seasons overlap, according to Kinney.