Today, despite medical progress, too many people are still dying, especially children, because they suffer from hunger and disease. On the other hand, contraceptives are used to plan families and their offspring so that there is as little overpopulation as possible. As the example of China shows, the fear of the aging of society is greater. One more child may be conceived than in the past decades. The climate - or perhaps better because of the weather - is changing negatively due to C02 and other industrial emissions. Global warming and warming of seawater, considering the floods, droughts and storms, also have negative rather than positive overall living conditions. I am not aware of any direct global influence of weather / climate on the birth rate with worldwide effect. But maybe there is.
In a away, infertility in women may be due many to sources that cut across physical and spiritual worlds. Climate change has not yet been scientifically proved to be the direct cause of infertility. However, it may be a contributory environmental physical factor.