Getting factual information is an essential part of any research, scientific or not. This was the purpose of the first section. But to begin understanding how the various parameters interact with each other, one needs to revert to established laws of physics and chemistry, or to propose new ones if sufficient evidence allows to do so.

Temperature is designated as the leading indicator for climate change. However, while it may be a necessary driver, it is far from being sufficient for fundamentally changing the climatic conditions under which an individual is living on some place of the earth. For example the Roman and the Medieval warm periods, and the Little Ice Age of the 16-17^th centuries are relatively small variations of the predominantly temperate climate that has prevailed in Europe since the beginning of the Holocene.

Physical laws, or theories, are different from models that will be discussed in the next chapter. They have been proven correct within their range of application by the evidence of mathematical cohesiveness of the relatively simple equations on which they are based, corroborated by experimental tests. Unless falsified by contradictory evidences, they are deemed valid.

The major physical laws that can be used when discussing climate change have all to deal with heat and mass transfers, and with electromagnetic radiations.