These days we hear a lot about the greenhouse effect - the earth is heating up - sea levels are rising as the polar ice melts - great storms sweep across continents. What should concern us is not the existence of the greenhouse - that is a good thing - but the fact that the amount of heat is increasing.
If we continue as we are then, in time, the Earth may become too hot for our own comfort. Remember - our species, like all others, has a limit for its span on Earth. It should be our responsibility to live on the Earth in such a way as to maintain the balance that allows life as we know it to continue.