It's all so confusing: CO2 allegedly increases Alaskan snowpack when that's needed for one bad scenario, but it also allegedly *decreases* Alaskan snowpack when that's needed for a different bad scenario.

Health: Climate change is expanding allergy risks -- 04/30/2012 -- www.eenews.net

A rising atmospheric carbon dioxide concentration is also important because it nourishes plants, and fast-growing pollen producers like ragweed are often the quickest to avail themselves of its increasing abundance.

...A changing climate also increases the likelihood of extreme weather events like heavy rainfall, which can exacerbate allergies from mold spores. Rotkin-Ellman cited the aftermath of Hurricane Katrina in New Orleans as an example of this. "It wasn't only dangerous levels of mold spores in homes, but all of the elevated levels of flooding created spores in the air as a whole," she said.

...This comes largely from warmer winter temperatures leading to more snowfall, since Alaskan winters often reach the point where it's too cold to snow. The snow helped insulate insect dwellings, and as a result, more stinging insects survived the winter and expanded their ranges. Now people are finding out the hard way whether they are allergic to stings.

Birch trees, a major pollen source in Alaska, have also benefited from the recent climate changes. "Not only is there a likelihood we are insulating the insect queen's hibernaculum, the snowpack also protects the trees and it protects the roots," said Demain. "As the permafrost melts, we're seeing trees grow where there have never been trees."

Flashback | Warming blamed for yellow cedar die-off in Southeast Alaska

Those roots turned into an Achilles heel as snow patterns changed. Elevated mortality began around 1880-1890 and peaked in the 1970s and 1980s, according to the USFS study.

The yellow cedar's durability allowed dead trees to stand 100 years after they died but the cause of death was perplexing for years. Tree pathologists eliminated organisms or fungi as the primary cause and turned to physical factors such as hydrology and soil temperature, eventually linking yellow cedar decline to snow accumulation and duplicating results with seedlings.

"It's ironic that a species might be dying due to freeze-induced mortality when the climate signal is warming," Schaberg said. "So the world is getting warmer and these things are freezing? What's up with that?"