EXETER The impact of global warming over the next century may be even worse than predicted because high levels of ozone are reducing the effectiveness of plants as “carbon sinks”, research suggests.

Ozone is a form of oxygen that has different effects depending on where it is in the atmosphere. At high altitudes in the stratosphere, it forms of protective layer that shields the Earth from ultraviolet radiation, but in the troposphere, closer to ground, it is a greenhouse gas that warms surface temperatures. It is also toxic and stunts the growth of plants. Carbon dioxide, by contrast, helps plants to grow, though it is also a powerful greenhouse gas. The ability of plants to absorb carbon dioxide depends on the interplay between these two factors.

Research by the the Met Office’s Hadley Centre for Climate Prediction and Research, published in the journal Nature, found that the overall balance will be negative, forcing up global temperatures by between 2.4C (4.3F) and 6.4C (11.5F) by 2100.

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