The adage "a little knowledge is a dangerous thing" is well illustrated by the letter from A T Sayers (WMN Nov 29).
The writer has plainly put a lot of thought into this, but, by starting from at least two false premises, he (if you are a lady, I apologise) has come to a conclusion that is not only wrong but also, if it leads anyone to ignore the potential of climate change, very dangerous.
First, if the average temperature of the Antarctic is -49C (I do not know if this is correct, but will assume it is). This means that some parts are colder than this and some parts are warmer and, during the summer, the average temperature will be warmer than this, whilst, during the winter, it will be colder. Thus, it is not necessary to raise the whole of the Antarctic to above 0C in order for melting to commence.
Melting of the ice cap will commence at the periphery of the polar cap, and this has been, and is being, observed. If, during colder spells, that water refroze, all would be well. However, it does not. Again, this has been, and is being, observed. The polar cap is generally white. This reflects the sun's radiation. The sea is darker and absorbs it. As the ice of the polar caps melts, the proportion of ice to sea changes: there is more sea, less ice. Therefore, as the ice melts, more solar radiation is absorbed, thus raising the sea temperature, the air temperature and ultimately the temperature of the Antarctic. We then get a vicious circle. The more ice that melts, the less there is to reflect solar radiation and the more sea there is to absorb it, leading to yet more ice melting and so on.
Vast quantities of methane are apparently trapped in permafrost. Methane is an even more effective greenhouse gas than carbon dioxide and, if this is released, we can expect the gradual increase in average global temperatures, which is currently being observed, to rapidly accelerate.
Global warming is happening. That is an observed fact. Most scientists believe that this warming will continue and that it is wholly or largely caused by human activities; these are hypotheses, but are accepted by the vast majority of scientists working in this field. It is, of course, possible that they might be wrong, but what is the downside if they are? Simply that we have devoted some of our wealth to renewable energy.
On the other hand, what is the downside if they are right and we choose to ignore them and do nothing or too little? At best, the seas will rise, devastating many countries, destroying many cities and killing several billion human beings and animals, and leaving those humans that survive forever on the verge of starvation. At worst, we could face a runaway cycle of warming, leading to the extinction of all or most life on this planet. The potential consequences of ignoring global warming are too horrendous to contemplate. If there were even only a small chance of it happening, we should do whatever we can to prevent it.