In the most recent ‘Garden’ magazine of the Royal Horticultural Society there is a small piece at the bottom of page 33 confirming that CO2 levels are now above 400 ppm (parts per million). Measuring started in 1957 when levels were at 317 ppm and ice core data shows we have to go back over 3 milion years to find levels higher than they are now. Between 3 and 5 million years ago levels were at 415 ppm, average global temperature was 3 – 4 degrees centigrade higher than today and sea levels between 5 and 40 metres higher.
Comment: The levels did rise above 400 ppm in May and have subsequently fallen back slightly. A current figure can be found at http://keelingcurve.ucsd.edu/ (398 ppm as I write this). However the general trend is most definitely upwards!
A couple of radio programmes you may find interesting:
Start the Week on Radio 4 discusses the impact of the global poulation reching 10 Billion
and also on Radio 4 Shared Planet – can we put a price on nature?