I am glad that there were encouraging comments on The Times' website following my rather controversial letter on climate change titled New Cars Can Be Worse Polluters (April 12).

For those who were somewhat confused I would like to say that I am not saying that old cars do not pollute the environment. This is so obvious that I felt there was no need to make a fuss on it. On the other hand, one must not continue to believe that new cars are virgins!

The reason is that when it comes to the global issue of climate change, it is the colourless, odourless carbon dioxide (CO2) which is of major concern and not the black exhaust that we often see coming out of worn-out or badly-tuned car engines.

As CO2 is given off by every combustion engine, it goes without saying that in order to have a fair tax on cars it would make more sense if we follow my genuine advice of: the more CO2 you produce, the more you have to pay.

For obvious reasons, several owners of new cars may probably be afraid of my fair-for-all proposal as they wouldn't want to take any risks.

Oops! As a matter of fact, last time I forgot to write that the wind-screens of modern cars have grown bigger than those of previous ones! Cars have literally become mobile greenhouses.

This means that the heat inside is much more unbearable than inside the older, cooler versions. This implies that nowadays, air conditioning has become a must and this in turn leads to more strain on the engine to produce more CO2.