Researchers from the Smithsonian and the University of Arizona have developed the most detailed temperature curve of Earth over the past 485 million years, revealing significant fluctuations and a strong correlation between carbon dioxide levels and global temperatures.
This new understanding underscores the unique rate of modern anthropogenic warming, posing risks to global ecosystems and sea levels.
A new study co-led by the Smithsonian and the University of Arizona offers the most detailed glimpse yet of how Earth’s surface temperature has changed over the past 485 million years. In a paper published on September 19, in the journal Science, a team of researchers, including paleobiologists Scott Wing and Brian Huber from the Smithsonian’s National Museum of Natural History, produce a curve of global mean surface temperature (GMST) across deep time—the Earth’s ancient past stretching over many millions of years.
The new curve reveals that Earth’s temperature has varied more than previously thought over much of the Phanerozoic Eon, the past 540 million years of geologic time when life has diversified, populated land and endured multiple mass extinctions. The curve also confirms that Earth’s temperature is strongly correlated to the amount of carbon dioxide in the atmosphere.
Innovative Methods in Climate Research
The team created the temperature curve utilizing an approach called data assimilation. This allowed the researchers to combine data from the geologic record and climate models to create a more cohesive understanding of ancient climates.
“This method was originally developed for weather forecasting,” said Emily Judd, the lead author of the new paper and a former postdoctoral researcher at the National Museum of Natural History and the University of Arizona. “Instead of using it to forecast future weather, here we’re using it to hindcast ancient climates.”
Implications for Understanding Modern Climate Change
Refining how Earth’s temperature has fluctuated over deep time provides crucial context for understanding modern climate change.
“If you’re studying the past couple of million years, you won’t find anything that looks like what we expect in 2100 or 2500,” said Wing, the museum’s curator of paleobotany whose research focuses on the Paleocene–Eocene Thermal Maximum, a period of rapid global warming 55 million years ago. “You need to go back even further to periods when the Earth was really warm, because that’s the only way we’re going to get a better understanding of how the climate might change in the future.”
Historical Climate Trends and Modern Concerns
The new curve reveals that temperature varied more greatly during the Phanerozoic than previously thought. Over the eon, the GMST spanned between 52 and 97 degrees Fahrenheit (11–36 degrees Celsius). Periods of extreme heat were most often linked to elevated levels of the greenhouse gas carbon dioxide in the atmosphere.
“This research illustrates clearly that carbon dioxide is the dominant control on global temperatures across geological time,” said Jessica Tierney, a paleoclimatologist at the University of Arizona and a co-author of the new paper. “When CO2 is low, the temperature is cold; when CO2 is high, the temperature is warm.”
The findings also reveal that the Earth’s current GMST of 59 degrees Fahrenheit (15 degrees Celsius) is cooler than Earth has been over much of the Phanerozoic. But greenhouse gas emissions caused by anthropogenic climate change are currently warming the planet at a much faster rate than even the fastest warming events of the Phanerozoic. The speed of warming puts species and ecosystems around the world at risk and is causing a rapid rise in sea level. Some other episodes of rapid climate change during the Phanerozoic have sparked mass extinctions.
“Humans, and the species we share the planet with, are adapted to a cold climate,” Tierney said. “Rapidly putting us all into a warmer climate is a dangerous thing to do.”
Exploring Past Climates to Inform the Future
The new paper is part of an ongoing research effort that began in 2018, when Wing, Huber and other Smithsonian researchers were helping develop the museum’s “David H. Koch Hall of Fossils— Deep Time.” The new hall aimed to put the museum’s fossils in context by highlighting how Earth’s climate has changed over the past half-a-billion years. For example, several specimens—including fossilized palm fronds found in Alaska—attest to a period in Earth’s past when global temperatures were much warmer than today.
The team wanted to provide museum visitors with a curve that charted Earth’s GMST across the Phanerozoic, which began around 540 million years ago and continues into the present day. But Wing and Huber were surprised to find that a reliable temperature curve for this period did not yet exist. This is largely due to the fragmentary nature of the fossil record. Fossil specimens offer some clues about ancient temperatures—for example, the chemistry of fossilized shells offer insights into oceanic temperatures in the distant past—but these are only isolated snapshots of one region at a single time. This makes it difficult to decipher what ancient temperatures looked like on a global scale.
“It is like trying to visualize the picture of a 1,000-piece jigsaw puzzle, when you only have a handful of pieces,” Judd said.
The Challenges of Reconstructing Ancient Temperatures
To produce a temperature curve across deep time, Wing, Huber and their colleagues started the PhanTASTIC (Phanerozoic Technique Averaged Surface Temperature Integrated Curve) Project. In 2018, the museum hosted a workshop for paleoclimatologists from across the country. In 2020, Judd arrived at the museum as the PhanTASTIC Postdoctoral Fellow to lead the project.
To create an accurate curve, the PhanTASTIC team used data assimilation. Meteorologists use data assimilation to combine observations of various factors like temperature, humidity and wind speed with weather models to create more accurate forecasts. In a similar vein, the team reconstructed climatic snapshots of the world at various points across the Phanerozoic by integrating data related to ancient ocean temperatures from different parts of the planet with computer simulations of past climates.
The team compiled more than 150,000 published data points from five different geochemical archives (or “proxies”) for ancient ocean temperatures that are preserved in fossilized shells and other types of ancient organic matter. Their colleagues at the University of Bristol generated more than 850 model simulations of what Earth’s climate could have looked like at different periods of the distant past based on continental position and atmospheric composition. The researchers then used data assimilation to combine these two lines of evidence and create the a more accurate curve of how Earth’s temperature has varied over the past 485 million years.
A Continuing Quest for Climate Knowledge
While the new paper is the most robust study of temperature change to date, it is far from a finished project according to Huber, the museum’s curator of foraminifera (amoeba-like single-cell organisms) who studies microscopic fossil shells to understand environmental conditions during the Cretaceous period, the warmest stretch of the Phanerozoic.
“We all agree that this isn’t the final curve,” Huber said. “Researchers will continue to uncover additional clues about the deep past, which will help revise this curve down the road.”
For more on this research, see Exploring Earth’s Climate Shifts: From Ice Ages to Heatwaves Over 485 Million Years.
Reference: “A 485-million-year history of Earth’s surface temperature” by Emily J. Judd, Jessica E. Tierney, Daniel J. Lunt, Isabel P. Montañez, Brian T. Huber, Scott L. Wing and Paul J. Valdes, 20 September 2024, Science.
DOI: 10.1126/science.adk3705
In addition to Judd, Tierney, Huber, and Wing, Daniel Lunt and Paul Valdes of the University of Bristol and Isabel Montañez of the University of California, Davis were coauthors on the study.
The research was supported by Roland and Debra Sauermann through the Smithsonian, the Heising-Simons Foundation, the University of Arizona’s Thomas R. Brown Distinguished Chair in Integrative Science and the United Kingdom’s Natural Environment Research Council.
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7 Comments
Does this reconstruction now constitute part of “the record”? If so, are we going to stop getting bombarded with false “warmest xxx on record” articles? The reconstruction discloses that we are in either the coolest or second coolest period of the last 450 million years and that the average temperature of the planet has been more than 10 degrees Celsius hotter than it is today. So, 3 or even 5 degrees of anthropogenic warming does not get us back to the average temperature of the reconstructed time period.
Ancient ages? What if that presumption is wrong? We all know man designs testing to reveal what he wants to see, not what he does not expect to see.
Man’s presuppisitions have always
Interfered with Man’s perception of truth or lie. Uniformitarian religion dominates science.
“This discrepancy suggests that existing Phanerozoic temperature records may underestimate past
temperature change, …”
This isn’t too surprising. Time affects measurement data like a low-pass filter in an electrical circuit. In determining the age of proxies, with an uncertainty of a fixed percentage, the absolute uncertainty increases in direct proportion to the amount of time that has passed. Thus, in determining the slope (tangent to a line), the steepness uncertainty is directly related to the amount of time passed. Similarly, processes of diffusion of chemical constituents, accompanied by isotopic fractionation, disturbance by burrowing organisms, and the measurement uncertainties inherent in the proxy method used, all result in suppressing estimated temperature peaks and broadening the width of peaks and valleys.
“The findings highlight atmospheric carbon dioxide (CO2) as the dominant factor controlling climate variability throughout this period, offering new insights into the Earth’s climate sensitivity across long timescales.”
They don’t mention that juvenile water emanating from volcanoes will correlate with CO2. They also don’t mention the lapse rate. This is important because temperature varies significantly with elevation and one has to know quite a bit about the topography to dismiss it as not being a significant factor, especially during orogenies (mountain building episodes) when mountains were often higher than they are today, except maybe in the Himalayas. Because CO2 is acknowledged to be well-mixed, the elevation of land cannot be ignored. There is a problem in that as the mountains are eroded, little is left that can be used as terrestrial temperature proxies, except in lowland swamps. It would seem then that there would be a bias for higher temperatures from terrestrial rocks. However, while they are hind-casting ocean temperatures, the average land temperatures can affect the oceans, particularly in cooling them.
“Moreover, the findings demonstrate a strong link between global temperatures and atmospheric carbon dioxide levels, suggesting that CO2 has been the primary driver of climate changes over this period.”
“Correlation does not establish causation” is a truism that is often ignored. It is evident that, today, seasonal CO2 variations are driven by biology, particularly in the northern hemisphere. (CO2 builds up from Fall of one year to May of the following year, from decomposition of dead phytoplankton and leaf litter, and respiration of dormant trees; the atmospheric CO2 peaks in May, when trees start to leaf out, and declines rapidly until Fall.) Furthermore, during warm El Nino years, the Winter ramp-up of CO2 is steeper and has a greater range than other years, making it appear that temperature is driving CO2, not the other way around. During the COVID shutdowns, despite anthropogenic CO2 declines of about 6-10% for the year, and the month of April alone being about 14-18% less than the previous year’s anthropogenic emissions, the seasonal CO2 ramp-up graph is indistinguishable from the preceding or subsequent years. See Fig. 3 at the link below:
https://wattsupwiththat.com/2021/06/11/contribution-of-anthropogenic-co2-emissions-to-changes-in-atmospheric-concentrations/
Then there are the Law Dome ice cores (Antarctica) that suggest that CO2 follows temperature changes.
While there are good scientific reasons for believing that CO2 drives temperatures, the empirical support is not as strong as many claim. It would appear that there are feedback loops that moderate the theoretical impact. Claims that CO2 is the “dominant factor” in Earth temperatures is poorly supported, despite what most researchers claim.
Despite my criticisms of some points, I find this research to be one of the better papers I have read on paleo-temperature reconstructions.
The graph I’ve seen shows absolutely zero correlation between the temperature and the level of CO2 in the atmosphere. Therefore, your “innovative” methods of measuring ancient temperatures must consist of making sh!t up.
https://wattsupwiththat.com/2016/02/26/analysis-of-the-relationship-between-land-air-temperatures-and-atmospheric-carbon-dioxide-concentrations/
See particularly Figure 1. Approximately half the variance in temperature is explained by the CO2, but that doesn’t establish causation.
Behavioural science has consistently demonstrated that people are far from rational when making decisions. We tend to support our past decisions, even if new information suggests that they are wrong, we tend to think that examples that come readily to mind are more common than they are and, we are irrationally impatient.
I believe that is why, despite the overwhelming scientific evidence, and consensus about that scientific evidence, we as a society are underinvesting in addressing climate change. Even though this investment will be far less costly than the investments we will have no choice but to make in the future.
Uniformitarian religion dominates ignorance.