BBC News - Carbon emissions linked to Europe's hay fever rise

BBC News - Carbon emissions linked to Europe's hay fever rise: "Researchers from 13 EU nations analysed pollen levels for more than 20 species of tree and plant.

They found that many, including several that cause allergies such as hay fever, correlated with rising CO2 levels.

Presenting their study at the European Geosciences Union (EGU) annual meeting, scientists said city planners might need to review which trees they plant.

Hay fever and other allergies appear to be rising across Europe.

In the UK, GP diagnoses of allergic rhinitis, which includes hay fever, rose by a third between 2001 and 2005.

It has been suggested that higher temperatures might be causing plants to produce more pollen.

But by comparing pollen counts during relatively hotter and relatively cooler years, this latest study found temperature was not the cause.

Annette Menzel from the Technical University of Munich said other possible factors were eliminated as well.

'We thought the increase in the amount of pollen could be related to land use changes, but we don't observe this,' she told BBC News.

'We tried to link it to temperature, but that's not possible.

'So the only effect that's left would be a CO2 effect; and we know from experiments in the real world and in climate chambers that CO2 does promote the amount of pollen [that trees produce].'"