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;
Why global temperatures failed to correlate with the steady increase in carbon dioxide levels over the past 100 years;
Why changes in carbon dioxide levels lag temperature rise by some 800 years in Antarctica ice core records spanning 800,000 years;
Why the cessation of all commercial flights over Canada and the United States for three days after the September 11 terrorist attacks increased the diurnal temperatures measured over the US by more than 1 degree Celsius (this is explained by higher daytime temperatures and lower nighttime temperatures caused by the disappearance of contrails, Water vapour being the main component of contrails);
Why temperatures measured at the Hong Kong Observatory's headquarters are nearly always higher than at its Waglan Island station, especially at night; and
Why the observed extreme weather events are within the range of known natural variability.
Because carbon dioxide is not the main cause of global warming, reducing carbon emission cannot be the solution to limiting the potentially catastrophic impact of climate change.
Wyss Yim, Pok Fu Lam