Question

Scientists observe the thickness of a tree’s ____________________ to learn about past climate conditions.

Answer 1

the answer is bark they observe the thickness of a tree's bark


hope this helps:) good luck

Answer 2

Annual rings

Step-by-step explanation:

Tree' annual rings are made of alternate circles of spring and autumn wood. Thickness of annuals rings indicate the climatic conditions of the region. Since the conspicuous, wider ring of spring wood with are formed during spring season, presence of thicker annual rings indicate longer growing season and good water availability. Similarly, thicker annual rings indicate warmer climatic conditions while thinner rings indicate the cooler climatic conditions like that of temperate regions.