People have used wood for millennia for many purposes, primarily as a fuel or as a construction material for making houses, tools, weapons, furniture, packaging, artworks, and paper. The year-to-year variation in tree-ring widths and isotopic abundances gives clues to the prevailing climate at that time.
For clues about the climate of a place, we can look at variation in isotopic abundances or what other thing?
{'text': 'tree-ring widths', 'answer_start': 213}