Researchers have found that ozone, the chemical we can't live without, could also be the death of us, or at least a potent trigger for global warming. Stephen Sitch, from the UK's Hadley Centre, has found that ozone at ground level interferes with the ability of plants to soak up carbon dioxide, meaning future CO2 predictions could have been significantly under-estimated. Ground-level ozone, which is produced when sunlight interacts with airbourne pollutants, has been steadily increasing in concentration in recent years. It enters the leaves of plants via their stomata - mouths in the undersides of the leaves that allow CO2 from the atmosphere to enter. Once inside the plant it damages cells and stunts growth, reducing the amount of carbon dioxide the plant subsequently removes from the air. "Although increased CO2 in the atmosphere will have a "fertilising" effect on plants, rising ozone will nevertheless cut the amount of CO2 removed from the atmosphere. So we may have underestimated the size of the warming effect we're going to get," says Sitch.