Research has uncovered that Earth’s temperature has fluctuated dramatically over the past 485 million years, largely due to varying levels of atmospheric CO2.
This new understanding, achieved by merging geological data and climate models, shows our current climate changes are proceeding at an unprecedented speed compared to past natural events, indicating a dire need for addressing global warming.
A new study, published on September 20 in the journal Science, presents a curve of global mean surface temperature that reveals Earth’s temperature has varied more than previously thought over much of the Phanerozoic Eon. This was a period of geologic time when life diversified, populated land, and endured multiple mass extinctions. The curve also confirms Earth’s surface temperature is strongly correlated with the amount of carbon dioxide in the atmosphere.
Exploring Deep Time: The Phanerozoic Eon
The start of the Phanerozoic Eon 540 million years ago is marked by the Cambrian Explosion, a point in time when complex, hard-shelled organisms first appeared in the fossil record. Although researchers can create simulations all the way back to 540 million years ago, the temperature curve in the study focuses on the last 485 million years since there is limited geological data of temperature before then.
“It’s hard to find rocks that are that old and have temperature indicators preserved in them – even at 485 million years ago we don’t have that many. We were limited with how far back we could go,” said study co-author Jessica Tierney, a paleoclimatologist at the University of Arizona.
The researchers created the temperature curve using an approach called data assimilation. This allowed them 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, lead author of the paper and a former postdoctoral researcher at the Smithsonian National Museum of Natural History and the U of A. “Instead of using it to forecast future weather, here we’re using it to hindcast ancient climates.”
The Significance of Historical Climate Patterns
Refining scientists’ understanding of how Earth’s temperature has fluctuated over time provides crucial context for understanding modern climate change.
“If you’re studying the last couple of million years, you won’t find anything that looks like what we expect in 2100 or 2500,” said Scott Wing, a co-author on the paper and a curator of paleobotany at the Smithsonian National Museum of Natural History. “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.”
New Findings on Historical Climate Variability
The new curve reveals that temperature varied more greatly during the past 485 million years than previously thought. Over the eon, the global temperature spanned 52 to 97 degrees Fahrenheit. 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 Tierney. “When CO2 is low, the temperature is cold; when CO2 is high, the temperature is warm.”
Current Climate Trends and Historical Context
The findings also reveal that the Earth’s current global temperature of 59 degrees Fahrenheit is cooler than Earth has been over much of the Phanerozoic. But greenhouse gas emissions from human-caused climate change are currently warming the planet at a much faster rate than even the fastest warming events of the Phanerozoic, the reseaerchers say. 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.
Rapidly moving toward a warmer climate could spell danger for humans who have mostly lived in a 10-degree Fahrenheit range for the global temperatures, compared to the 45-degree span of temperatures over the last 485 million years, the researchers say.
“Our entire species evolved to an ‘ice house’ climate, which doesn’t reflect most of geological history,” Tierney said. “We are changing the climate into a place that is really out of context for humans. The planet has been and can be warmer – but humans and animals can’t adapt that fast.”
The collaboration between Tierney and researchers at the Smithsonian began in 2018. The team wanted to provide museum visitors with a curve that charted Earth’s global temperature across the Phanerozoic, which began around 540 million years ago and continues into the present day.
Combining Data for a Comprehensive Temperature Curve
The team collected more than 150,000 estimates of ancient temperature calculated from five different chemical indicators for temperature that are preserved in fossilized shells and other types of ancient organic matter. Their colleagues at the University of Bristol created 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 combined these two lines of evidence to create the most accurate curve of how Earth’s temperature has varied over the past 485 million years.
Climate Sensitivity Across Geological Eras
Another finding from the study pertains to climate sensitivity, a metric of how much the climate warms for the doubling of carbon dioxide.
“We found that carbon dioxide and temperature are not only really closely related, but related in the same way across 485 million years. We don’t see that the climate is more sensitive when it’s hot or cold,” Tierney said.
For more on this research:
- Exploring Earth’s Climate Shifts: From Ice Ages to Heatwaves Over 485 Million Years
- Earth’s Climate Transformation: 485 Million Years of Change Powered by CO2
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 are coauthors on the study.
The research was supported by Roland and Debra Sauermann through the Smithsonian; the Heising-Simons Foundation and the University of Arizona’s Thomas R. Brown Distinguished Chair in Integrative Science through Tierney; and the United Kingdom’s Natural Environment Research Council.
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10 Comments
Ah, the old curve didn’t fit the narrative, so they had to “recalculate” it. There goes the science.
“…, our current climate changes are proceeding at an unprecedented speed compared to past natural events, …”
That is little more than an opinion, poorly supported by data. For starters, time acts like a low-pass filter, suppressing the range and increasing the width of peaks and valleys in the temperatures. That is exacerbated by using proxies for past events because there isn’t perfect correlation between the independent variable (proxy) and the predicted dependent variable. The calibration procedure of fitting a line to the plot of the two variables removes all the peaks and valleys and assumes that the prediction is correct when it may, and often does, have large uncertainties. For a fixed-percentge error, the absolute error for things like age/time, increase in direct proportion to the amount of time passed. Instrumental measurements should never be assumed to be equivalent to estimates derived from proxies! Predictions from models are rarely as reliable as proxies, and depending on them to fill in gaps in proxy estimates is probably little better than simple interpolation. In any event, missing data is just that — missing data. Temperature or precipitation could be higher or lower during the time of the missing data. One simply does not know! The formal uncertainty (margin of error) should increased any time that model or proxy data are combined with actual instrumental measurements. However, the uncertainty is rarely even reported, let alone be accompanied by a rigorous propagation of error calculation.
“This research illustrates clearly that carbon dioxide is the dominant control on global temperatures across geological time,”
No! It only demonstrates correlation, not cause-and-effect. There are numerous counter examples that are best explained by the working hypothesis that increasing temperatures (particularly above the melting point of water) cause an increase in CO2, rather than what the authors have unjustifiably assumed. (It is the unexamined assumptions that often lead one astray.) It is probably more complex than that, with it being a feedback loop where both are happening. However, it is my opinion that the net effect is that temperatures are driving CO2 concentration.
Climatologists using computer models (GCMs) depend on what are called ensembles, which are the total results of numerous models with different assumptions and starting conditions. Climatologists then use the mean of those predicted runs, for a particular scenario, as though it were reality. Rarely is there any thought given to the uncertainty in that ‘correct’ prediction. Probably, because they don’t really know what the correct value is. However, there is what is called the Empirical Rule in statistics that says a first-order approximation of the standard deviation, for normally distributed measurements, is about 1/4 the range. Using that, however, would give an uncomfortably large uncertainty. Therefore, the whole question seems to just be ignored. However, to properly put the forecasts, or backcasts in this case, into perspective, researchers should provide that information to allow their peers to judge the utility of claims based on very large uncertainties.
Consider this: Logically, there can only be one best model, ignoring ties. If that best model is averaged with all those that are inferior, the result will be inferior unless it happens to be in the middle of the range. It is difficult to prove the ranking of accuracy. However, it should be noted that the Russian models have routinely best matched reality, and they are the models that show the least recent increase in temperature.
Clyde Spencer has put the counter-argument perfectly. High temporal resolution Antarctic ice core data have shown that the atmospheric CO2 rise does not precede temperature rise, it is actually the other way around. So, correlation does not indicate causality, but this assumption of causality is the foundation for all Climate Change related policies that are being adopted around the world. It’s not science, it is dogma.
The statement “our current climate changes are proceeding at an unprecedented speed compared to past natural events” is simply not true. GISP2 ice core data (from Greenland) have shown that annual average ice temperatures have fluctuated significantly and continuously over the past 4000 years, with temperature swings as rapid as 1.9°C in as little as a year, and with slightly slower yet consistent swings spanning up to 150 years – all of which were completely natural variations, and had nothing at all to do with variations in the amount of atmospheric greenhouse gases.
….that is little more than an opinion, poorly supported by data……
Of course. That is always the excuse.
The Industrial revolution began in around 1640 when some Earl, of probably Northumberland, began underground coal mining on his land and increased when steam powered weaving mills got going to mass-produce cotton fabrics. Back in Cokedale in the Severn Gorge a bloke called Derby started using coking coal to make coke to smelt iron and built the cast-iron Severn Bridge. So let’s say that that is 400
+\-50 years during which we humans have burnt enough hydrocarbon fuels to increase atmospheric C02
from approx. 270ppm to 425pp.
Did it not take the Siberian Traps event an even shorter time in which to change the atmosphere so that 90% of all then then life progressively died out? No. That outgassing event may have been as short as 60 000 years but is not 400+\-50years. Of course not 90% of all life has died out since 1640; it doesn’t need to as the stress that Anthropogenic Global Heating is putting on, and will further put on, 8 billion people living in societies fully dependent on complex human infrastructure, the least complex of which is a continuous supply of clean drinking water, will lead to civil strife and warfare. And that is the problem as our weapons are now far too powerful to be managed H sapiens , which is an aggressive and very stupid animal even at the best of times.
And that is a fact conveniently forgotten/ignored by such as the above commentators.
Are you aware that there is a high correlation between drownings and ice cream sales? You don’t seem to understand that the “fact” of a correlation does not establish causation. Look up “spurious correlation.”
“Of course not 90% of all life has died out since 1640; …”
Probably because life has done well under even warmer conditions than the End-Permian, such as during the Eocene. The cause of the extinction probably had more to do with the noxious gases emitted by the coal and other carbon-rich sediments intruded by sills, baking them, and driving off the volatiles. The coal would have released a Witch’s Brew of coal tars (think benzene), mercury, carbon monoxide, and sulfur dioxides, along with the typical volcanic gases. The land flora and fauna began dying first. [ https://scitechdaily.com/in-earths-greatest-extinction-land-animals-began-dying-off-long-before-marine-life/ ] As they were dying off, bacteria would consume them and release CO2 into the atmosphere. Eventually, the strong acids (sulfuric from the pyrite in the coal being oxidized, and hydrochloric and hydrofluoric from volcanic emissions) would have actually acidified the oceans, killing the fish, which CO2 alone can’t do because the oceans are so strongly buffered against CO2 induced changes. Deep, stagnant pools rich in organic material also produce toxic hydrogen sulfide.
“There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy.” — Hamlet
https://scitechdaily.com/mercury-pollution-and-mass-extinction-tracing-toxic-legacies-from-earths-volcanic-past/
As Clyde, you must be aware, there is a high correlation between bloody-minded wilful idiocy when driving a car and getting someone smashed up and even getting killed oneself.
You simply pick nits and quibble about how many angels ride on their backs. That is, you quite deliberately ignore the social reality of human nature and the result of 400 or so years of H sap trying to make life more comfortable; everything is always a trade-off. The present minuscule global warming of 1.5 degrees +\-0.3 degrees C is that trade-off. However, that is enough to change sea level and melt our frozen water-supply in the Himalaya/Andes etc quickly enough to unbolt fractured rock on over-steepened slopes as well as reduce the available water over which we will fight serious wars. e.g nuclear-armed Hindu India v. nuclear-armed Muslim Pakistan.
I think some former fellow scientists once invented the word ‘entropy’ to describe the idea.
I am very well aware of such items as how life has adapted itself to this planet as well as to how life has adapted this planet to life. I recognised the Global Snowball as a most-probable concept, the alternative being the Earth’s axis lying in the plane of the Earth’s orbit, a year before it took someone the time the effort and the academic setting to research adequate data to publish the idea completely independently; the Global Snowball concept was at the time blatantly obvious from new palaeomagnetic data and glacial sedimentology, but needed considerable testing and fine-tuning to become acceptable to academia.
Your first sentence is essentially a non sequitur. What is your point?
I’m not quibbling about numbers that can’t be measured. When I see something that is illogical, or is contradicted by facts, I point it out. I see poor quality research coming out that many accept based on it coming from an ‘authority.’ I’m appealing for higher quality research and better peer review because our survival depends on it. Politicians who don’t understand science think that they know what is best for society and are all too ready to dictate changes that could be more threatening to our survival than an increase of 1 deg C per century that might even be cyclical.
As an illustration that you are not a deep thinker, consider the following: Should it suddenly turn much colder, as it did in the most recent Little Ice Age, there would be less runoff from the Himalayas. Thus, there would be a water shortage. Temporarily, the best outcome for those in India and Pakistan would be for the climate to not change. However, that isn’t what climates do. There is an old saying that “The only thing that is constant is change.” Even if the climate were to stay constant, the increasing population would create a greater demand for water. There is no chance that a colder climate will provide more water, and an improbable constant climate will also encounter water shortages with an increasing population. Probably the best ‘solution’ would be to acknowledge that people are an example of too much of a good thing, and be thankful that increased melting of the frozen water buys time for a solution to the human problem.
Here’s a thought… first, recognize that over 70% of the earth’s surface is water; when the earth cools, gasses in the atmosphere are stored in these waters and vice versa, as per Charles Law. So the largest “gas storage bank” of atmospheric gases, when not in the atmosphere, is in planet earth’s waters.
Then there’s this… https://www.energy.gov/articles/top-6-things-you-didnt-know-about-solar-energy
Each hour, 430 quintillion Joules of energy from the sun hits the Earth. That’s 430 with 18 zeroes after it!
In comparison, the total amount of energy that all humans on planet Earth use in a year is about 410 quintillion Joules.
The Sun has 10,000 times more impact on Earth’s temperature / climate than the entire human race.
So, would it not make sense that when the sun heats up the earth, including all its waters, that gases stored in the earth’s waters are released into the atmosphere, including CO2.
This truly is the “chicken or the egg” story; the version depends on the funding stream. Perhaps a question for Bill Gates, eh?