2014 was the hottest year on Earth since recordkeeping began in 1880, and ten of the previous warmest years on record occurred since 2000. The scientific consensus is that climate change is the driving force behind these rising temperatures. Scientific studies have also shown that our changing climate could favor the formation of more ozone smog in some areas and increase the production of allergenic pollen such as that released by the ragweed plant, the principal source of pollen associated with allergic rhinitis. This is bad news for allergy sufferers and asthmatics because both ragweed pollen and high levels of ozone smog can trigger asthma attacks and worsen allergic symptoms in adults and children. Moreover, studies show that people exposed to both ragweed allergens and ozone are likely to become more ill than people exposed to just one of the two. These negative health effects are expected to worsen if carbon dioxide (CO2) concentrations keep rising and climate change continues unchecked.