Diverse and detailed data show that climate has always been in a state of change. Climate is driven by radiation energy from the Sun, and for this reason we begin by presenting the basic physics of thermal radiation. Next we will look at the origin of climate and describe some of the many factors that are responsible for natural climate variation. Finally, we will examine natural and anthropogenic factors that are known to have driven climate change since 1750 AD, and some possible climate futures will be discussed. One of the main challenges for the next generation of chemists will be to solve the issues described here that link chemistry, energy, and environment.

Evidence for long-term climate variation can be found in the glacial ice of Antarctica and Greenland, and in deep-sea sediments containing shells from plankton. These records are interpreted by examining changes in the abundance of naturally occurring stable isotopes, for example, oxygen isotopes in water in the ice or in the carbonates of sediments, and sulfur isotopes in pyrite and calcium sulfate in shallow-water sediments. Long-term climate changes are correlated with changes in the Sun-Earth geometry as a consequence of the interaction of the Earth with the Sun and its planets.