Atmospheric carbon dioxide levels have scaled record highs. CO2 has hit 381 parts per million - 100ppm above the pre-industrial average, the BBC reports.

Researchers at the US National Oceanic and Atmospheric Administration analysed air samples the world over. The benchmark findings mean the rate of increase in CO2 has doubled in the last 30 years.

Chief analyst Pieter Tans said: "We don't see any sign of a decrease; in fact, we're seeing the opposite, the rate of increase is accelerating."

Government chief scientific adviser Professor Sir David King said: "That's higher than we've been for over a million years, possibly 30m years. Mankind is changing the climate."

The worrying data comes as Australian scientists report unprecedented levels of coral bleaching on the Great Barrier Reef, caused by abnormally high sea temperatures. Coral bleaching occurs when the tiny animals that build the structures die away.

Added to this, ahead of a UN environment ministers meeting due to be held later this month, biodiversity pressure group Diversitas has warned that environmentally-sensitive amphibian populations are being decimated.

Amphibians are often a barometer of how ecosystems respond to stressors, such as global warming, and so the group submits the outlook for diversity is grim. Diversitas head Anne Larigauderie told Reuters: "We are facing an extinction crisis." She poured scorn on the UN goal of significantly slowing species loss: "It's totally unrealistic." ®