Madam, - John Gibbons is to be complimented on his timely and informative series on climate change. However, his article of May 22nd, "EU's CO2 goal may be ecological suicide", gives prominence to scientific results that need to be regarded with a degree of scepticism.
He quotes the findings of a group of US scientists indicating a need for much more drastic and immediate cuts in CO2 emissions than have been judged necessary by the EU on the basis of the 2007 report of the Intergovernmental Panel on Climate Change (IPCC).
The scientific results quoted are based on a study of ocean sediments from 35 million years ago, when the atmospheric CO2 level was 450ppm and sea levels were 75 metres higher than today. With present emissions, this level of CO2 will again be reached in the present century. The conclusion presented by Mr Gibbons, apparently as a result of a conversation with the main author of the US study, is that something like 75 metres of sea level rise will necessarily ensue.
The primary cause of the extreme climate of 35 million years ago, however, was not CO2 increase but, most likely, variations in solar heating due to the varying tilt of the earth's axis or the shape of its orbit. Changes in greenhouse gas concentrations would occur in response to such variations in solar heating and would amplify their effect. Water vapour, the main greenhouse gas in the atmosphere, would be the main amplifier and CO2 a secondary one.
In contrast, the primary cause of global warming today is, with virtual certainty, the increase in CO2 due to human activities. However, the solar heating pattern of 35 million years ago is missing in today's climate and a CO2 level of 450ppm in this century, even though it will represent a serious perturbation to the natural climate system, will not necessarily be attended by the same effects as in that distant era.
Limits on CO2 emissions will have painful consequences and arguments for making them more stringent need to be based on solid scientific evidence. Adequate grounds for alarm are provided by the IPCC report and by the subsequent evidence of rapid decrease of the Arctic sea ice. The environmentalist case can only be weakened by adding evidence that is clearly dubious.
Despite my reservations about his sources in this instance, I
wish Mr Gibbons every success in his laudable project of conveying
scientific information on climate matters to the public. - Yours,
etc,
RAY BATES,
Adjunct Professor of Meteorology,
UCD,
Belfield,
Dublin 4.