The samples, which formed about 14,000 years ago as the ice age drew to an end, contains bursts of nitrous oxide, popularly known as laughing gas.
The gas, used medically for pain relief has gained notoriety in recent years thanks to people using it as a recreational drug. A study by Mirjam Pfieffer of the Swiss Federal Institute of Technology, in Lausanne, found that nitrous oxide which ended the Ice Age came from plants that blossomed as the climate began to warm.
The team reconstructed how the ecosystem changed at a Swiss lake during this time by identifying pollen buried in sediment. As temperatures rose, the area was over-run by a shrub called sea buckthorn. Sea buckthorn uses nitrogen from the air to produce nutrients. Trials suggest that its chemical tinkering released a lot of nitrous oxide, perhaps 1.6 mg of extra gas for every square metre of land. The scientists said told New Scientist magazine that a similar development could happen this century as Arctic ice retreats and warmer Arctic peatlands belch out nitrous oxide.