Carbon dioxide cuts cannot be solution to global warming

Tania Willis' letter ("Personal action now unavoidable to halt planet's destruction", June 1) quoted Al Gore and Jim Hansen in labelling carbon dioxide as the primary global warming pollutant. She has fallen short in showing why the 7.2 million people in Hong Kong must hold their breath because of the undesirable consequences claimed by her.

"Climate Change: A Summary of the Science", based on the consensus opinion of Royal Society scientists and issued in September 2010, provides the best synopsis on the current science on climate change.

It shows where the science is well established and where there remains substantial uncertainty.

Measurements from the earth's surface and space, together with modelling, show that, in addition to clouds, the gases that make the largest contribution to the greenhouse effect are water vapour, followed by carbon dioxide. There are smaller contributions from many other gases, including ozone, methane, nitrous oxide and chlorofluorocarbons.

Therefore the effectiveness of reducing the second most important greenhouse gas carbon dioxide alone is questionable. Carbon dioxide alarmists must also explain:

Why carbon dioxide is labelled as a pollutant when it is an essential, life-supporting part of earth's ecosystem;

Why the current 400 parts per million level of atmospheric carbon dioxide is more important to global temperatures than clouds and water vapour;