There is much confusion about some of the basic principles of climate variability and change. We will discuss several key concepts that are relevant for climate change, present observational evidence of climate change, and present what climate models tell us is in store for the future. We will discuss strengths and weaknesses of our understanding and the uncertainties, and we will show how the realities of climate change emerge from an objective assessment of the available information. Analogies will be drawn with other fields where useful information about ongoing and future changes can be provided in a framework that allows for uncertainties.