More CO2 means larger poison ivy plants and more toxic oil per plant.
In a more acidic ocean, shellfish, plankton and corals struggle to adapt.
CO2 mixes with seawater to form carbonic acid, making the oceans more acidic.
If CO2 emissions continue at the current pace, pollen counts are projected to nearly double by 2060.
Spring is arriving earlier across the U.S. by an average of three days.
Scientists say increased CO2 emissions are making poison ivy worse.
Foliage color and timing has been starting later, on average, in a warming world.
The highlights of NOAA's 2013 Spring climate summary.