Ancient climate

5 ways scientists read Earth’s history

All around us, Earth harbors secrets of its past.

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Minerals, fossilized pollen, air bubbles in ice, ocean critters’ shells and more hold molecular signals of past climates.

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These are called “climate proxies,” and scientists use them to study how Earth’s climate has shifted — how rains come and go, how temperatures rise and fall, how storms become stronger or weaker.

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Reading Earth’s history in the rocks and trees offers an intimate understanding of ancient shifts in climate, scientists can improve on current models to predict our future.

Here are 5 ways nature records past climates — and how scientists study them to understand our future.

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JoAnna Wendel

Cave formations like stalactites and stalagmites form when water droplets evaporate and leave behind layers of minerals, building up a column of rock.

JoAnna Wendel

Molecular signatures inside these tiny layers of mineral tell scientists whether a period of time was more wet or more dry.

JoAnna Wendel

Tree rings can also reveal the past. Depending on the growth requirements of a tree, the thickness of each ring varies in different temperatures and conditions.

JoAnna Wendel

For example, if a particular tree depends on wet conditions to grow, thicker rings mean the climate was wetter, too.

Sediment textures can tell scientists about stormy conditions in the ancient past.

JoAnna Wendel

Intense storms tend to stir up coarser sediment and calm conditions deposit finer sediment, so scientists can investigate the frequency of ancient storms using layers of rocks.

JoAnna Wendel

JoAnna Wendel

Tiny marine organisms called foraminifera build shells using molecules from ocean water.

JoAnna Wendel

Like cave formations, scientists use molecular signatures in these shells to learn about past ocean conditions, including whether sea temperatures were hotter or cooler.

Air bubbles trapped in ice record climate.

JoAnna Wendel

By studying the gases in ancient air bubbles, scientists can piece together periods of temperature change.

JoAnna Wendel

Read more science and nature stories here.

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