Episode 113 – Paleoclimate

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Life on Earth is directly impacted by the climate, and the climate changes over time in response to the activities of tectonic plates, ocean currents, biological communities, and of course, even humans. The geologic record of our planet is an archive of data on the causes and effects of changing climates. This episode, we discuss Paleoclimate.

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Climate Past and Present

No matter where you are on the surface of the Earth, life is strongly influenced by climate. Climate is the long-term average of weather, including temperature, precipitation, humidity, and more, typically averaged over 30 years. The term is often used to refer either to the local conditions in a particular place on Earth, or to the overall conditions of the planet’s climate system.

Köppen-Geiger Climate Classification Map, one method of displaying climate regions on Earth. Click here to see the map legend.
Image by Beck et al. / CC BY-SA 4.0

Climatologists monitor the climate by combining meteorological tools (thermometers, barometers, etc.) with computer models that simulate the Earth’s complex climate systems. This information allows us to keep track of trends in the climate and to make predictions about climate in the future. As you can imagine, climate data is useful for biologists, geologists, meteorologists, tourists on vacation, and plenty more.

Climate Change

The Earth’s climate changes over time, and as it does, it impacts biological and geological processes on the planet, so paleontologists are very interested in understanding the climate conditions at different points in the past.

The history of Earth is a history of changing climate. This graph shows how temperatures have changed over the past 500 million years, with increasing resolution in more recent time periods.
Image by Glen Fergus / CC BY-SA 3.0

Climate data can be collected from a variety of sources, including ancient sediments, ice layers, shelled organisms, plant leaves, and plenty more. As conditions like temperature and precipitation change, this can leave recognizable changes in the distribution of plants and animals, or in the chemistry of minerals in the sediment or in the shells of sea creatures like foraminifera. These indicators of ancient climate are called proxies, and a collection of proxy data (like layers of sediment, ice, or cave minerals) are called archives.

This episode’s guest, Dr. Rachel Lupien, studies paleoclimate.
Left: Dr. Lupien visiting Norway to core the paleoclimate archive of lake sediments (this is the location she referred to as “Hoth” in the episode!)
Right: In the lab, Dr. Lupien uses liquid chromatography to gather leaf wax compounds from African lake sediments. These compounds are an important proxy for climate data.
Images from Dr. Rachel Lupien

Putting together paleoclimate data can help us understand the causes and effects of changing climate. Volcanic activity or asteroid impacts can fill the atmosphere with dust; changes in the Earth’s orbit can affect how sunlight reaches the surface; changing ocean currents and shifting continents can impact how heat and moisture are distributed around the planet – all of these are factors that can cause the climate to change on local or global scales. And when climate changes, it leaves its mark in the plants, animals, rivers, and even rocks on the surface.

Many times in Earth’s history have seen rapid climate change, often with dramatic effects, including the end-Cretaceous extinction, the Paleocene-Eocene Thermal Maximum, and the end of the Pleistocene Epoch. On the other hand, slow change can be impactful as well: the gradual cooling over the course of the Cenozoic Era is a major factor in the spread of grasslands and the success of animals like horses.

Over the last several decades, climate data shows that most parts of the world have seen an increase in average temperature between a few degrees and several degrees. Our climate is changing rapidly.
Image by NASA’s Scientific Visualization Studio / Public Domain

Studying the Earth’s climate history provides us with a long list of case studies to help us understand the causes and effects of changing climate. This is, of course, especially important nowadays. Climate data from the past and present make it unambiguously clear that our own human activities – the release of carbon dioxide into the atmosphere via burning fossil fuels – are causing a rapid rise in average global temperatures. This shift has been linked to changes in storm patterns, sea ice distribution, habitats for plants and animals, and more. As humans around the globe continue to discuss how to limit our impact on climate and how to handle the changes we’ve already kicked off, scientists look to the past to study how climate changes and what happens when it does.

Learn More

Explore more about Paleoclimatology on the websites of the USGS, NOAA, and SERC.

Tierney et al. 2020. Past climate inform our future. A new paper about the importance of paleoclimate studies in understanding future global warming and related processes.

Learn more about current climate change with NASA’s page Climate Change Evidence, and with Global Weirding, a YouTube channel about modern-day climate change with Dr. Katharine Hayhoe

How to Save a Planet is a podcast about how to solve the climate crisis.

The Green New Deal is a proposal by United States politicians that we mentioned in this episode. It sets a number of policy goals related to mitigating and managing the effects of climate change.

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