Have you been sneezing and experiencing watery eyes nonstop lately whenever you step outside? It’s not just us — around the world, people are facing an intense pollen “surge.” Are pollen impacts really getting worse? In this episode of Global Weather Early Warning Watch, we look at the pollen challenge under climate change.

First, let’s look at the data. According to the World Health Organization (WHO), 30% to 40% of the global population has suffered from allergic diseases. Alarmingly, by 2050, as many as 4 billion people worldwide could be affected by allergies. Among all types of allergic diseases, pollen allergy is on a steady rise and has become the leading cause of allergic conditions.

Why is pollen allergy getting worse? Two key factors are driving this trend.

The WHO points out that, amid global climate change, rising temperatures and increasing carbon dioxide levels are causing pollen seasons to start earlier and last longer, boosting pollen production and increasing the risk of pollen allergies.

　　Figure 1. Effect of climate change and air pollution on pollen and allergic diseases

First, rising global temperatures are bringing spring earlier, which in turn significantly advances the start of pollen seasons. Data from the USA National Phenology Network shows that the average start of spring across the 48 contiguous states has been getting earlier since 1984. Between 1990 and 2018, due to earlier springs, total pollen production across the United States surged by 21%.

　　Figure 2. Global annual average temperature anomalies from 1850 to 2024, relative to the pre-industrial baseline (1850–1900).(Source: World Health Organization)

This pattern is seen worldwide. In Canada, the ragweed pollen season extended by more than three weeks between 1995 and 2009. In the United Kingdom, plants now bloom 4.5 days earlier on average than a decade ago. Pollen seasons are also lengthening in European countries such as Poland and Italy.

With earlier springs and longer pollen seasons, our exposure to pollen is increased — so it’s no wonder allergy risks are soaring.Second, soaring carbon dioxide levels act like a growth hormone for plants.

The World Meteorological Organization (WMO) reports that global atmospheric CO₂ reached 420 ppm in 2023, 151% of the pre-industrial level. Carbon dioxide is essential for plant photosynthesis. Higher CO₂ levels supercharge photosynthesis, acting as an “accelerator” for highly allergenic plants like ragweed and mugwort, greatly increasing their pollen output.

　　Figure 3. Globally averaged CO₂ concentration (a) and its growth rate from 1984 to 2024(Source: World Meteorological Organization)

Since we can’t avoid pollen entirely, we must take proactive steps. Beyond daily protection, we must also address the challenge of climate change together. Share this video to remind family and friends to stay protected and get through pollen season safely.

Author：ZHOU Ying Editor: ZHOU Ying