Trees in the greenhouse

According to research using isotopically labeled carbon dioxide to study a mature forest outside the Swiss town of Basel, trees do not grow more in an atmosphere more rich in carbon dioxide, but simply "pump" through more CO2 than normal. Scientists at the Paul Scherrer Institute (PSI) and the University of Basel developed a new system to distribute CO2 to the treetops and found that contrary to general expectations there was no sustainable increase in biomass carbon. The question of whether or not rising atmospheric carbon dioxide levels would cause forests to grow more quickly and so store more carbon has vexed environmental scientists for years.