WEATHER | DISEASE | WATER | HUNGER | AIR POLLUTION | ALLERGIES 
There is growing evidence that rising global temperatures are affecting both the timing and abundance of airborne allergens, especially pollen.
In recent decades, spring flowering, and thus the allergenic pollen season, has advanced at a rate of nearly a day per year. In the Mediterranean, the leaves of most deciduous plant species now unfold on average 16 days earlier and fall on average 13 days later than they did 50 years ago, whereas in Europe, spring events, such as leaf unfolding, have advanced by about six days per decade since the 1950s. Experimental studies have demonstrated significant increases in pollen production resulting from exposure to increased CO2 concentrations, while examination of recent trends have linked elevated pollen levels to increases in temperature.
Studies also suggest stronger allergenicity of pollen from trees grown at increased temperatures. A study in Pediatrics warns of the potential public health consequences of these changes: "climate change may adversely impact the occurrence and severity of asthma, the most common chronic disease of childhood, and affect the timing or duration of seasonal allergies such as hay fever." Combined with the observed doubling of pediatric asthma prevalence within the past twenty years, children's physiological and behavioral susceptibility to air pollution increases their risk of being adversely affected by changes in the concentration and distribution of pollutants.
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