Using Fossils To Battle Climate Change

Instead of relying on (or denying) what mathematical models predict about global warming, we can learn from the past.

Paleontologists study fossils to understand past life on Earth. Unfortunately, our science has some limitations. We can’t travel back in time to understand what past ecosystems looked like or what dinosaurs’ behavior was. Thus, we rely on “clues,” which has led many to describe our experts as “detectives of the past.”

However, our science also has some advantages. We may not be able to comprehend time snapshots fully. For example, we can’t know precisely what happened the day the meteorite that led to the death of dinosaurs hit the Earth. But fossils have a window to two very unique sources of data: 1) changes through long periods of time and 2) significant events with no precedents in human history.

German academic Wolfgang Kiessling and his collaborators recently published a peer-reviewed article showcasing how paleontological studies can help organizations like the Intergovernmental Panel on Climate Change (IPCC). The authors talk about their own experience with this organization and highlight an important message:

[…] paleontology allows a systematic assessment of past impacts of climate change, permitting us to find generalities of past responses to climate change, which can be incorporated in projections — Kiessling, et.al., 2023

We know that the Earth has experienced climate change in the past. Thus, paleontological researchers understand the vital role we play in understanding the effects that climate change can have on modern ecosystems. In particular, we have been addressing the biotic responses to these events.

‘Biotic responses’ are changes in living organisms — such as plants or animals — or ecosystems in response to an ‘abiotic’ event such as climate change, droughts, or rising sea levels. The essential tool that paleontological and paleo-climatological studies offer is the study of these biotic responses under extreme circumstances, such as global warming events or increased greenhouse emissions.

As climate, greenhouse concentrations, and biodiversity on Earth changed, they left traces on the forming rocks. If we want to know how these events affect our planet, we don’t need to wait and see what happens; we can analyze rocks and fossils to determine the answer from equivalent past events.

Is modern climate change part of Earth’s cycles?

Our studies provide a counter-argument to climate skeptics claiming that climate change is a normal process due to orbital changes, known as the Milankovitch cycles. These cycles repeat on time scales ranging from 26,000 to 100,000 years, affecting the amount of radiation the Earth receives. These cycles can also explain changes in Earth’s climate, especially regarding the Glacial-Interglacial changes over the last 450,000 years.

However, we know that these cycles are not to blame for the rapid warming we are experiencing at present. How do we know? As stated on NASA’s website, “Over the last 150 years, Milankovitch cycles have not changed the amount of solar energy absorbed by Earth very much. In fact, NASA satellite observations show that solar radiation has decreased somewhat over the last 40 years.” In other words, we should currently see global cooling, not global warming.

What we do see, though, is an increase in greenhouse gases above the common fluctuations observed during these 450,000 years. And we were able to measure this from ancient ice sheets, rocks, and fossils.

Is it just the Temperature we should worry about?

If we want to understand better the impacts of greenhouse gases on the climate and the ecosystems beyond temperature changes, we should look into longer time spans. Ancient hyperthermal events, driven by volcanically-induced greenhouse gas emissions, are potentially more representative of scenarios we may face shortly.

As briefly explained in my previous story, these emissions have led to more than temperature changes throughout history. Studying the fossil and geological record during those times may help us further.

As highlighted in the figure above and my previous story, geologists and paleontologists have identified six significant episodes of increasing atmospheric carbon dioxide in Earth’s history. One of them, the End-Permian Hyperthermal Event (~252 Million Years Ago), led to Earth’s most traumatic mass extinction event. This is something extremely relevant to the present since we are also dealing with a 6th Extinction threat (the Earth has experienced five major mass extinctions in the past).

The amounts of carbon dioxide released to the atmosphere through volcanic activity during the End-Permian Hyperthermal Event were way beyond what we may see now. But another carbon dioxide emitting episode better resembles what we see now: the End-Triassic Hyperthermal Event (~201 Million Years Ago). We are still investigating this event, but we already know that the consequences were devastating for life and Earth’s systems.

In 500-year episodes, volcanoes released the same amount of carbon dioxide that we are projected to release during the 21st century alone. This event led to a global warming of +6°C. Additionally, about three-quarters of all species died out. All Triassic archosaurs, apart from dinosaurs, pterosaurs, and crocodiles, went extinct. Marine wildlife took the most significant toll.

Why did species die out? As the climate got warmer, sea levels began to rise, and the oceans became more acidic alongside large-scale changes to the global carbon cycle. Acidification affects many animals’ ability to make shells or skeletons, which they need to survive. This promoted extinction events within marine ecosystems that soon translated to extinction events on land.

As you can see, there is more than global warming regarding increased greenhouse gases. Check out the PBS Eons video below, which expands on a similar event that occurred a few million years later during the Cretaceous Oceanic Anoxic Event 2a.

The study of the fossil record provides a unique window to understanding what the cascading effects of human-induced greenhouse emissions and global warming could have on the Earth as a system. While humans weren’t causing these gases in the past, our emissions mimic some of the most catastrophic events led by massive volcanic eruptions.

Some critics raise concerns that climate science is unreliable because it lacks experimentation and replicability. However, geology and paleontology offer a unique methodology for providing these necessary tools. Instead of denying what mathematical models say about the consequences of global warming and greenhouse emissions, we need to further compare these models with what we can learn from the past. By doing so, we will get the necessary answers.

For example, paleontological data has been incorporated into the study of the effects of climate change on sea level change. With cities like Miami, FL, or Savanah, GA, entirely submerged by the end of the century, the results should have us actively seeking solutions. However, that’s a story for another day. Stay tuned for more.