Paleontologists examine fossils to decipher the history of life on our planet. Regrettably, this branch of science encounters certain constraints. We must wait to venture back in time to observe ancient ecosystems or the behaviors of dinosaurs firsthand. Consequently, we depend on “indications,” earning our specialists the moniker “detectives of bygone eras.”
Nonetheless, this field boasts distinct advantages. Although we cannot capture exact moments from the past—such as the precise events of the day a meteorite caused the extinction of dinosaurs—fossils offer a glimpse into two exceptionally unique data sources: 1) evolutionary changes over extended periods and 2) unparalleled events in human history.
German scholar Wolfgang Kiessling and his team recently unveiled a peer-reviewed study demonstrating how paleontological research can assist entities like the Intergovernmental Panel on Climate Change (IPCC). The researchers share their experiences with this organization and emphasize a crucial point:
[…] paleontology facilitates a systematic evaluation of historical climate change impacts, enabling the identification of consistent patterns in past climate responses, which can be integrated into future forecasts — Kiessling et al., 2023
It’s acknowledged that our planet has undergone climate alterations previously. Thus, paleontological investigators recognize the critical role they play in comprehending the consequences climate change may impose on contemporary ecosystems. Specifically, we’ve been exploring the biological reactions to these phenomena.
‘Biotic reactions’ refer to adjustments in living beings—such as flora or fauna—or ecosystems reacting to an ‘abiotic’ occurrence like climate change, droughts, or elevating sea levels. The invaluable resource offered by paleontological and paleo-climatological research is the examination of these biotic reactions under severe conditions, like global warming events or increased greenhouse gas emissions.
As climate, greenhouse gas concentrations, and biodiversity on Earth evolved, they imprinted on the forming rocks. To understand the impact of these events on our planet, we don’t have to wait for future outcomes; we can study rocks and fossils to glean insights from analogous historical occurrences.
Is the current climate change a component of Earth’s natural cycles?
Our investigations offer a rebuttal to climate change skeptics who argue that climate change is a natural phenomenon resulting from orbital variations, known as Milankovitch cycles. These cycles, which recur over 26,000 to 100,000 years, influence the amount of solar radiation Earth receives. They also explain climatic shifts, particularly concerning the Glacial-Interglacial transitions over the past 450,000 years.
However, these cycles do not account for the swift warming currently observed. How are we confident? As noted on NASA’s website, “Over the past 150 years, Milankovitch cycles have not significantly altered the amount of solar energy Earth absorbs. NASA satellite data indicate that solar radiation has slightly diminished over the past 40 years.” Therefore, we should be witnessing global cooling, not warming.
However, a rise in greenhouse gases is observed beyond the natural variations noted during these 450,000 years. This was confirmed through ancient ice sheets, rocks, and fossils analyses.
Is Temperature the Only Concern?
Examining more extended historical periods is essential to understand the impact of greenhouse gases on the climate and ecosystems beyond mere temperature fluctuations. Events of ancient hyperthermal, triggered by volcanic greenhouse gas emissions, might offer a closer parallel to the challenges we could soon face.
As outlined briefly in my preceding article, these emissions have historically led to more than temperature changes. Delving into those eras’ fossil and geological records could provide additional insights.
As depicted in the previously mentioned figure and article, geologists and paleontologists have pinpointed six critical instances of rising atmospheric carbon dioxide levels in Earth’s history. Notably, the End-Permian Hyperthermal Event (approximately 252 million years ago) precipitated Earth’s most severe mass extinction event. This is relevant today as we confront the possibility of a sixth mass extinction (following five major ones in Earth’s history).
The volume of carbon dioxide released into the atmosphere from volcanic activity during the End-Permian event far exceeds current levels. However, the End-Triassic Hyperthermal Event (around 201 million years ago) presents a closer analogy to contemporary conditions. Ongoing research into this event has already revealed its catastrophic impacts on life and Earth’s systems.
Volcanic eruptions over 500-year spans released carbon dioxide amounts projected for the 21st century alone, leading to a global temperature rise of +6°C. Moreover, roughly three-quarters of all species became extinct, including all Triassic archosaurs except dinosaurs, pterosaurs, and crocodiles, with marine life suffering the most significant losses.
Why did these species vanish? Rising temperatures caused sea levels to elevate and oceans to acidify, alongside significant alterations to the global carbon cycle. Acidification hampers the shells or skeleton formation of many animals, which is essential for survival, thereby triggering extinction events in marine ecosystems that soon extended to terrestrial realms.
Thus, the issue extends beyond global warming when considering the effects of increased greenhouse gases. The PBS Eons video below further explores a similar phenomenon occurring millions of years later during the Cretaceous Oceanic Anoxic Event 2a.
Fossil record studies offer a distinctive lens to view the potential domino effects of human-induced greenhouse gas emissions and global warming on Earth as a holistic system. While human activity did not cause these past emissions, our current emissions resemble those from significant volcanic eruptions known for their devastating consequences.
Some skeptics argue that climate science lacks reliability due to its perceived absence of experimentation and replicability. However, geology and paleontology provide a unique approach to supplying these essential tools. Rather than dismissing what mathematical models predict about the effects of global warming and greenhouse emissions, comparing these models with historical data could yield vital insights.
For instance, paleontological evidence has been integrated into studying the effects of climate change on the rise in sea levels. With cities like Miami, FL, and Savannah, GA, at risk of submersion by the century’s end, the urgency for solutions is apparent. Yet, that discussion is for another time. Stay tuned for further exploration.