Wind-pollinated plants—including trees, grasses, and weeds—produce most of the pollen that affects seasonal allergy sufferers. Wind-pollinated plants produce great amounts of pollen grains that are very small in size. For example, one ragweed plant can produce 1 billion dustlike pollen grains. These small pollen grains are capable of travelling long distances by the wind, potentially affecting large numbers of people who suffer from pollen allergies. Allergy symptoms can range from nuisance manifestations, such as itchy eyes and runny nose for those with allergic rhinitis (also known as hay fever) to severe health hazards for those with allergic asthma. Unfortunately for those who suffer such allergies, researchers in North America and Japan have reported earlier start dates for pollen seasons as well as increased concentrations of airborne pollen. These increases have occurred since (in North America) and before (in Japan) 1990, and the researchers attribute these changes to global climate change. See also: Allergy; Asthma; Global climate change; Pollen
Climatic factors influencing pollen production include warmer spring and fall temperatures, which extend the growing seasons of pollen-producing plants, and increased atmospheric carbon dioxide (CO2) concentrations, which may cause plants to produce even more pollen. Climate simulations by researchers at the University of Michigan, United States, show that by the end of this century in North America, spring pollen season could start 10 to 40 days earlier, while increases in temperature and atmospheric CO2 concentrations could increase pollen production by 200 percent. As climate change has already increased the length of pollen seasons in recent decades, the outlook for allergy sufferers seems somewhat unfavorable. See also: Carbon dioxide; Global warming; Greenhouse effect; Plant growth; Simulation
