Today, we can measure temperature with a simple glass thermometer, but the thermometer appeared in the 1700s.
So how can we know temperatures thousands or even millions of years ago? How can we understand the climatic conditions of those periods?
They’re looking at ice sheets.
Ice sheets in polar regions, including Greenland, Antarctica and North America, can provide us with information about ancient temperatures. The snow that falls every year forms a new layer of ice on top of the previous one.
Since these layers, which are formed at different temperatures and have unique chemical properties, are preserved, scientists can easily examine them and have an idea about the temperature conditions of certain time periods.
Tree rings are another method.
The rings visible in a horizontal section cut from the trunk of a tree can be wide or narrow, depending on the current climatic conditions in which the tree grows. Therefore, tree fossils help scientists predict changing weather conditions.
Even pollen can be checked.
Plant pollen is highly resilient and highly dependent on current weather conditions. The abundance or scarcity of their presence in a particular geographical region gives a clue as to how hot or cold that region was in the past.
Finally, lake and ocean sediments.
Deep sediments found at the bottom of bodies of water such as lakes and oceans are a great source of information about ancient temperatures. The most important of these deposits are layers of shells of small, surface-dwelling animals deposited over millions of years.
Scientists examining the oxygen isotopes found in these sediments provide information about weather conditions dating back to the age of dinosaurs.
Of course, there are other methods, but none of these methods give clear results. We can only reach an approximate estimate.
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