HD Osborn's claim (Letters, NCE 13 May) that while 'humans have created a little extra CO 2it has a minimal effect on global warming' is illfounded.
Concentrations of atmospheric CO 2have shown a rapid acceleration since the Industrial Revolution and present day levels are at their highest in the 420,000 year record. Measurements of CO 2show a 33% increase since 1760.
This is primarily due to combustion of fossil fuels and can hardly be said to constitute 'a little extra CO 2'.
This has occurred even though the oceans have taken up around a third of the additional CO 2. Increases in atmospheric CO 2have been mirrored by a significant increase in the mean global temperature of approximately 0.6infinityC, and even higher over land. An immediate stabilisation of CO 2would still see an increase in warming of around 1infinityC owing to the inertia of the climate system. With more realistic scenarios of greenhouse emissions, temperatures are set to rise considerably further.
Far from the ocean being the main driver of current climate change the evidence supports the assertion that anthropogenic CO 2is by far the bigger influence.
Fiona Smith, Met Office, Hadley Centre for Climate Prediction and Research, FitzRoy Rd, Exeter EX1 3PB