The amount of carbon dioxide in the air is growing at alarming rates and is now at levels not seen for millions of years. The dangerous levels of CO2 could fuel a 20-metre rise in sea levels and add 3 degrees to temperatures, the World Meteorological Organisation said.
Levels are accelerating far faster than before, with last year's growth more than 50 per cent above the average for the last decade. That has led CO2 levels to rise 45 per cent above pre-industrial levels and further outside the range of 180-280 ppm seen in recent cycles of ice ages and warmer periods. As far as anyone can tell, the world has never experienced a rise in CO2 levels as quick or intense as this. The increase has happened 100 times faster than when the world was emerging from the last ice age.
The last time carbon dioxide levels reached 400 ppm was 3-5 million years ago, in the mid-Pliocene era.
"During that period, global mean surface temperatures were 2-degrees warmer than today, ice sheets in Greenland and West Antarctica melted and even parts of East Antarctica's ice retreated, causing the sea level to rise 10-20 m higher than that today," the WMO bulletin said.
The two other main gases - methane and nitrous oxide - also grew to record concentrations last year, although at a slower rate of increase than carbon dioxide.
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