How hot did Earth get in the past?
By Judy Holmes, Syracuse University (press release)
The question seems simple enough: What happens to the Earth’s temperature when atmospheric carbon dioxide levels increase? The answer is elusive. However, clues are hidden in the fossil record. A new study by researchers from Syracuse and Yale universities provides a much clearer picture of the Earth’s temperature approximately 50 million years ago when CO2 concentrations were higher than today. The results may shed light on what to expect in the future if CO2 levels keep rising.
The study, which for the first time compared multiple geochemical and temperature proxies to determine mean annual and seasonal temperatures, is published online in the journal Geology, the premier publication of the Geological Society of America, and is forthcoming in print Aug. 1.
SU Alumnus Caitlin Keating-Bitonti ’09 is the corresponding author of the study. She conducted the research as an undergraduate student under the guidance of Linda Ivany, associate professor of earth sciences, and Scott Samson, professor of earth sciences, both in Syracuse University’s College of Arts and Sciences. Early results led the team to bring in Hagit Affek, assistant professor of geology and geophysics at Yale University, and Yale Ph.D. candidate Peter Douglas for collaborative study. The National Science Foundation and the American Chemical Society funded the research.
“The early Eocene Epoch (50 million years ago) was about as warm as the Earth has been over the past 65 million years, since the extinction of the dinosaurs,” Ivany says. “There were crocodiles above the Arctic Circle and palm trees in Alaska. The questions we are trying to answer are how much warmer was it at different latitudes and how can that information be used to project future temperatures based on what we know about CO2 levels?”
Previous studies have suggested that the polar regions (high-latitude areas) during the Eocene were very hot—greater than 30 degrees centigrade (86 degrees Fahrenheit). However, because the sun’s rays are strongest at the Earth’s equator, tropical and subtropical areas (lower latitude) will always be at least as warm as polar areas, if not hotter. Until now, temperature data for subtropical regions were limited.
The SU and Yale research team found that average Eocene water temperature along the subtropical U.S. Gulf Coast hovered around 27 degrees centigrade (80 degrees Fahrenheit), slightly cooler than earlier studies predicted. Modern temperatures in the study area average 75 degrees Fahrenheit. Additionally, the scientists discovered that, during the Eocene, temperatures in the study area did not change more than 3 to 5 degrees centigrade across seasons, whereas today, the area’s seasonal temperatures fluctuate by 12 degrees centigrade.
The new results indicate that the polar and sub-polar regions, while still very warm, could not have been quite as hot as previously suggested.
The findings are based on a chemical analysis of the growth rings of the shells of fossilized bivalve mollusks and on the organic materials trapped in the sediment packed inside the shells, which was conducted by Keating-Bitonti and her colleagues. Ivany collected the fossils from sediment layers exposed along the Tombigbee River in Alabama. The mollusks lived in a near-shore marine environment during a time when the sea level was higher and the ocean flooded much of southern Alabama. The sediments that accumulated there contain one of the richest and best-preserved fossil records in the country.
“Our study shows that previous estimates of temperatures during the early Eocene were likely overestimated, especially at higher latitudes near the poles,” Keating-Bitonti says. “The study does not mean elevated atmospheric CO2 levels did not produce a greenhouse effect—the Earth was clearly hotter during the early Eocene. Our results support predictions that increasing levels of atmospheric CO2 will result in a warmer climate with less seasonality across the globe.”
To determine the average seasonal temperatures in the study area, Keating-Bitonti sampled the mollusk shells for high-resolution oxygen and strontium isotope analyses, which were done at SU. The Yale team analyzed shells and sediments for clumped-isotope and tetraether-lipid analysis. The results were consistent across all of the independent analytic methods. The scientists believe the multiple methods of analysis have yielded a more complete and accurate picture of ancient climate than previously possible.
The study also marks the first time clumped-isotope analysis has been used alongside traditional oxygen isotope and organic geochemical analyses in paleoclimate work. The research team is currently using the same analytical process to determine Eocene Epoch mean annual and seasonal temperatures in polar-regions.
“Clumped isotopes is a new way to measure past temperatures that offers a distinct advantage over other approaches because the technique requires fewer assumptions; it’s based on well understood physics,” Affek says. “The agreement among different methods gives us confidence in the results and enables us to use these methods in other locations, such as Antarctica.”
Keating-Bitonti recently completed a master’s degree in geology at the University of Wisconsin and will be continuing her studies at Stanford University as a Ph.D. student in the Department of Geological and Environmental Sciences, School of Earth Sciences.
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h/t to Dr. Leif Svalgaard
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One site, and the Global/Arctic/Antarctic temps are known????
Kind of like, “Here let me use analytical extension to encompass the poles…” er, I’m sorry that works only in complex analysis, not in climate – back to the drawing boards guys.
A couple of years ago, I quoted Dr. Tim Patterson whose geological studies came up with the same information. He should be given some credit.
http://hallofrecord.blogspot.com/2009/10/co2-be-afraid.html
South Alabama is a proxy for Arctic temperatures….
…the MWP was local
Like wsbriggs, I am probably more skeptical that people can gather accurate temperature data from 50-million-year-old fossilized mollusks than I am that they can gather useful data from tree rings. And because gauging the accuracy of temperature estimations of a climate 50-million years in the past is impossible, studies like this one seem like a complete waste of resources. Blech,
I love this blog. We get real science in full context. Not deceptive headlines or cherry picked excerpts intended to reinforce some discredited ideological goal.
Crocodiles at the North Pole. Give the polar bears something to worry about.
There’s a good bit of web info on clumped isotopes, but I can’t imagine being able to find any kind of lipids from that long ago.
“Ivany collected the fossils from sediment layers exposed along the Tombigbee River in Alabama.”
An awfully small sample area to hang a global temperature on.
How would they know what temperature range it was in the polar regions? From samples in Alabama.Only 2,500 miles to the south.
“Centigrade”? These days, it’s “Celsius.”
Pete
Due to plate tectonics, the configuration of land masses and ocean basins was not the same in the Eocene as now. This means that ocean heat transport was quite different, particularly the movement of heat from the equatorial Pacific Ocean to the northern Atlantic Ocean.
This is likely to affect the site studied more than the concentration of the CO2 in the atmosphere.
They are trying to keep their jobs as they realize the kebang is falling apart might as well get into some of what the skeptics have been sayin’ singin’ all along; There have been quite a few of these articles lately from the AGW establishment. THis will proceed until all interest in the subject is stone dead by both AGW and skeptics, believers and deniers LOL. Except that it will turn to solar so the solar scientist will be hot item on the agenda in the coming years. But what is the point of funding them because nothing can be done about that one More LOL.
On the plus side, I didn’t see anything about fossilized tree rings…
wsbriggs,
No, the article clearly states that they only claimed to have worked out subtropical and tropical temperatures. But since those temps are lower than or equal to what what polar temperatures were believed to be, this raises the possibility that polar temps have been overestimated. Or the new subtropical temps are wrong. Only time will tell, but the article also states that they now want to use the same technique to determine the temperature at higher latitudes. It seems your motto is “ready, fire, aim.” Read the whole article more carefully next time.
The study does not mean elevated atmospheric CO2 levels did not produce a greenhouse effect—the Earth was clearly hotter during the early Eocene.
Technically just about any CO2 should yield a “greenhouse” effect. The missing wording should say if there was an increased effect from the elevated CO2, as all the fun stuff gets invoked about CO2’s logarithmic response, response saturation, and whether feedbacks amplified or dampened the temperature response.
Our results support predictions that increasing levels of atmospheric CO2 will result in a warmer climate with less seasonality across the globe.
And as “less seasonality” means lesser temperature variations, there will be less of the severe weather seen during the transitions between the seasonal cold and warm periods. Sounds good. How much more CO2 do we have to emit to get to that nicer weather?
Attribution of higher temperatures 50 mya to CO2 alone forgets the effects of the geotectonic situation. Ocean currents were much different and certainly influence temperatures.
“Our study shows that previous estimates of temperatures during the early Eocene were likely overestimated, especially at higher latitudes near the poles,” Keating-Bitonti says. “The study does not mean elevated atmospheric CO2 levels did not produce a greenhouse effect—the Earth was clearly hotter during the early Eocene. Our results support predictions that increasing levels of atmospheric CO2 will result in a warmer climate with less seasonality across the globe.”
From the paper.
I guess I’m a chauvinist pig or something. As soon as I see a hyphened last name I immediately have bad thoughts,and even more after I see Wisconsin in the credentials.
So what caused the atmospheric CO2 levels to rise without man made emissions and then fall without an Australian carbon tax?
I believe someone is confusing cause and effect again…
This is news?
Let’s try again eh.
Every little bit of extra knowledge helps in understanding a complex system. I am intrigued that palm trees in Alaska must mean hotter temperatures than today despite their downward revision by this paper – there are palm trees in Scotland that survive today- ostensibly because of the “Gulf Stream” – I’ve seen them at Plockton which lies at about 57 degrees north and is somewhat inland sheltered from the coast – you can easily see photos of them in Google Earth.
So finding evidence of palm trees or crocodiles in locations which appear abnormal could be explained by mechanisms other than extreme temperatures – how about a few degrees C, a warmer current than today’s gulf stream and a bit of continental drift.
Anyway – this paper has reduced the extremes of the past back to more moderate values and helps expand our knowledge base.
Whether CO2 is a major or minor player in climate – I’m backing minor – expanding knowledge helps keep alarmism in check.
Eocene CO2 was high because of the high temperature, since the relatively weak effects of CO2 cannot alone explain any times in the past that were warmer than now. (Null hypothesis: CO2 has always been the follower, not the leader.) Rather, paleogeography & currents induced those higher temperatures, which led to higher CO2 and its weak warming, which was insufficient to prevent the cooling that came when the worldwide equatorial current was later abolished by the closing of the Tethy’s Seaway and the enclosure of the Med. The much later closing of the Strait of Panama was merely the coup de grace of WarmWorld (never to return), along with the establishment of the Circumpolar Antarctic Current.
By the way, nowhere in this article or the abstract cited was there any mention of what the authors think was the CO2 level then. The Warmistas should plug into their silly computer models the Earth’s Eocene paleogeography & currents, along with what they fantasize as the super-powerfull BUWAHAHA Satanic CO2 and its dreaded (fictional) positive feedbacks, and watch the Eocene oceans boil. Perhaps that would expose the essential shabiness of their vaunted simulations.
John of Cloverdale Perth WA says:
July 5, 2011 at 4:57 pm
What caused the atmospheric CO2 levels to rise was the Martians. After they wrecked Mars by playing with Doomsday devices which blew a hole into the crust we now know as Olympus Mons, they then proceeded to modify Earth correctly. Since Mars is now dead, and the secrets of the Martians died with them, any attempts at modifying Earth to satisfy paranoia over CO2 levels is likely to result in the 3rd dead Planet. Venus was the 2nd attempt, likewise a failure. Oops, we’re slap out of Planets to attempt modification, so it’s either adapt or…. Steps #9 & #10 as found on “In case of Nuclear Attack” instructions.
“The study does not mean elevated atmospheric CO2 levels did not produce a greenhouse effect—the Earth was clearly hotter during the early Eocene. Our results support predictions that increasing levels of atmospheric CO2 will result in a warmer climate with less seasonality across the globe.”
Sweet considering the global warming slew of extreme weather predictions…
How much data do some people have to see before they will finally, finally admit CO2 does not control climate?
John of Perth (been there, lovely little town) asked the primary question that no one can answer.
And the failure to be able to answer that question leaves the whole AGW argument in tatters.