Earth's climate is predicted to change rapidly with serious consequences for humanity. However, during its more than four billion years of existence, the climate on our planet has been changing continously, accompanied by more or less severe extinction events (for instance at the end of the Permian, some 250 million years ago, more than 85% of all lliving organisms on land and in the sea became extinct, due to a disastrous global warming caused among other factors by enormous volcanic eruptions). What is new today is, that while before the appearance of homo sapiens these climate changes had natural causes, and took place over long periods of time, in the present day human activity contributes considerably to the ill effects on our environment (including climate), as well as brings about change more quickly.