August 6, 2008 Seasonal allergies may be growing worse Play video

(NECN/ABC) - August 15th is the opening day for ragweed season and it is fast approaching, which is bad news for the 36 million Americans who suffer from ragweed allergy -- and global warming could be making things worse.

According to scientists' estimates, the planet is expected to heat up between two and four degrees this century. Allergy experts say the warmer temperatures are ALREADY making the pollen season worse for allergy and asthma sufferers -- a trend they expect will only accelerate in the coming years.

If it seems like your seasonal allergies have been getting worse in recent years, you may be right.

Experts from the American Academy of Allergy, Asthma & Immunology say GLOBAL WARMING is making pollen seasons LONGER and more concentrated.

In a new review, researchers describe multiple ways in which warmer temperatures impact asthma, allergies, and other respiratory disorders.

One British study on hundreds of plants found that they flower an average of nearly 5 days EARLIER now compared to a decade ago - and 10 percent flower a 15 days earlier, lengthening the allergy season.

Other research finds that increased carbon dioxide gas is linked to a 60 to 90 percent rise in pollen production for some ragweed varieties.

Global warming is also expected to create more FOREST FIRES, which trigger air pollution that worsens asthma.

Experts recommend allergy sufferers protect themselves by keeping their windows CLOSED

during the pollen season, STAYING INDOORS during midday to reduce exposure, and changing their CLOTHES after outdoor activities.

ABC's Dr. Timothy Johnson has more.