When I first studied history at school and then, to a degree later at university, there was a sometimes implicit assumption that climate was stable.
Obviously in any study of human pre-history the presence of climate change is taken as a given, something that affects the pattern of human life. In similar vein, the impact of climatic events such as cold spells or droughts in the historical period was known because it appeared in the historic record. Yet I think that it remains true that, unconsciously at least, we tended to assume for day to day purposes that these were variations within a pattern rather than variations in the climatic pattern itself.
I also think it true that we underestimated the importance of geography itself, of the interactions between geography and human life. Geography was there and important, but more or less as a framework within which activities occurred.
I discovered the importance of geography in history long ago. However, I now that find my lack of knowledge of the history of climate change has become a major defect.
Thanks to the current interest in climate change, we now know that there have been significant variations in the Australian climate even in the short period since European occupation of the continent. It is not just drought and flooding rains, but long periods of wetter and drier weather. The further we go back into the long period of human occupation of this continent, the more pronounced the changes become.
This pattern is not unique to Australia.
Each change has caused changes in the pattern of human life. The greater the change in terms of length and size, the greater the impact. There may be dispute about the detail as well as causation - the Little European Ice Age is a recent historical example - but it does seem clear that the effects have been substantial.