So yes, there will be more ragweed pollen, and somewhat more pollen from all plant species.

FORBES: Global Warmists Allergic To The Truth During Pollen Season

Such traits -- whether of viruses, ragweed pollen or cancer -- are called antigens.

FORBES: In search of antigens

Moreover, we are told, global warming is expanding ragweed range and the range of other nuisance plants.

FORBES: Global Warmists Allergic To The Truth During Pollen Season

Warmer temperatures, we are told, mean longer growing seasons and longer pollen seasons for nuisance plants such as ragweed.

FORBES: Global Warmists Allergic To The Truth During Pollen Season

Trees start scattering their pollen in early spring, followed by grasses, and then ragweed kicks in during the summer and runs through fall.

CNN: Predicting allergy season eludes experts

Dr Epstein offers a novel twist: he thinks that rising carbon dioxide concentrations may be promoting the growth of ragweed, pollen and fungus.

ECONOMIST: Climate change

But in the past researchers have focused on allergens in the air, Silverberg said, such as pollen or ragweed, instead of other environmental exposures.

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The spring allergy capitals are based on tree pollen counts, while the fall cities are ranked on ragweed pollen counts from September through November of the previous years.

CNN: Worst U.S. cities for allergy sufferers

"It's been a better year for ragweed, " Kress says.

CNN: Southern deluge may help fall allergy sufferers

Normal people also realize that it is better to have a world that is conducive to plant growth, even though ragweed is one of those plants, than to have a world that is hostile to plant growth.

FORBES: Global Warmists Allergic To The Truth During Pollen Season

Oh, wait, ragweed is a plant, too.

FORBES: Global Warmists Allergic To The Truth During Pollen Season

Although the South suffers from weed and mold spore allergies in the fall, Gerald Kress, an executive with SDI Health, which operates Pollen.com, says the North and Northeast gets hit particularly hard by ragweed -- and 2009 is shaping up to be a banner year for ragweed pollen.

CNN: Southern deluge may help fall allergy sufferers