According to the researchers, since 2005, the allergy season has increased by 16 days in Minneapolis -- and even farther north, as the number of frost-free days each year also rose.

This has been accompanied with food shortages in Africa, the demise of polar bears in the Arctic and massive flooding in Pakistan -- they may seem like remote symptoms of climate change to people in snow-struck Minnesota.

The researchers on Monday said that one price Minnesotans are already paying because of rising global temperatures is the extension of allergic season. This has increased another 16 days of suffering for about 10 percent of population. This allergy is caused by pollen grains and is very common for humankind.

"It isn't just theoretical", said Lewis Ziska, a plant physiologist with the U. S. Department of Agriculture, who led a study published in the Proceedings of the National Academy of Sciences.

He also claimed that the scientists have seen seasonal changes reflected in terms of the actual pollen season length.

"Climate change increases pollen production. There's more pollen on any given day", said Frenz. He also said the duration of the season is longer.

He analyzed 15 years of pollen data for eight cities that follow a south-to-north line from Georgetown, Texas, to Saskatoon, Saskatchewan, including Minneapolis.