People with seasonal allergies may be suffering sooner and for longer this spring. A new study in the Proceedings of the National Academy of Sciences found that climate change is causing plants to release their pollen earlier. The amount of pollen in the air is increasing each year. The extra pollen is mainly coming from trees. Extra carbon dioxide in the air makes the plants produce more pollen. Scientist Bill Anderegg lead the study. He expects this to gets worse in future decades.