How do scientists study Prehistory?

There are quite a few ways for scientists to determine old weather patterns. Firstly, old records are quite useful. Meteorological devices have been around for a very long time, in fact, Galileo Galilei created a thermoscope in the late 1500's that would be similar to the modern thermometer.

Another way is to determine the Climates in the past. This can be done through cutting down trees and examining the rings in the trunk. A tree develops about a ring a year, and if the ring is thick, the year had lots of rainfall, if it's thin, then there wasn't much rain. Some trees date back thousands of years giving long and accurate reports.

Scientists can also determine climate from studying rock faces and observing the mineral deposits. As rock accumulates on the surface certain minerals appear and disappear at certain rates. This can show wind patterns, water patterns, and the patterns of foliage and fauna on the surface at the time of rock's formation.

Thirdly, Scientist can study global climate through cutting cross-sections of ice out of glaciers or the ice caps where ice has been accumulating for millenia. They can see how much of certain gasses, or seeds, were in the air at times, and determine how those would affect the global climate.

Fourthly, in the same way scientists cut the ice, they can also cut mud or silt straight out of the ground and examine it for certain pollen types, fossils, artefacts, or other clues about old weather in that area.

Hope this helped!