The Heat Was On: Atmospheric CO2 Triggered a Global Warming Event 40 Million Years Ago

[one...two...tree 2,762]

In a new study scientists used "paleothermometers" to gauge CO2 and temperatures that prevailed during a long-lived primordial global warming event, and found CO2 to be the culprit

By Mike Orcutt

Atmospheric CO2 was the primary driver of a 400,000-year global warming event, known as the middle Eocene climatic optimum (MECO), according to a new study. The finding, which could help climatologists better understand the precise relationship between CO2 concentration and climate change today, is described in the November 5 issue of Science.

The climate trend across the entire Eocene, an epoch between 55 million and 34 million years ago, was actually characterized by long and gradual cooling. Much of that activity took place during the middle Eocene, when the planet transitioned from a warmer climate to a cooler one. But the MECO (about 40 million years ago) interrupted that trend, representing the last major temperature increase before the end of the epoch, which was marked by Antarctic glaciation. In order to investigate the role of CO2 during this warming episode, researchers analyzed sediment taken from deep beneath the ocean floor off the eastern coast of Tasmania. The core contained a record of fossils that spanned the relevant time interval.

The researchers relied on two separate organic proxies, also called paleothermometers, to reconstruct changes in sea-surface temperature during the MECO. Both are based on variation—due to temperature change—in structural characteristics of the molecular remains of specific microorganisms. In other words, the team analyzed specific molecules in which certain variations are known to be reflective of temperature change.

The MECO has for a long time been enigmatic to climate researchers, says study co-author Alexander Houben, a paleoecologist at Utrecht University in the Netherlands. Although there is lots of evidence for a large-scale temperature increase during this time, so far it's all been based on a different proxy: the occurrence of a specific oxygen isotope in ancient carbonate samples. Oxygen isotope values, however, are influenced not only by temperature, but also by seawater composition and changes in ocean ice flow. This study for the first time employs two independent proxies that "can clearly differentiate between temperature changes and other factors," Houben says. The authors report that the paleothermometers indicated a warming of the sea surface during the MECO, at least in the southwestern Pacific, by 3 to 6 degrees Celsius.

To figure out how much atmospheric CO2 increased during the MECO, the researchers reconstructed the changes in its concentration by determining the ratio of stable carbon isotopes in organic molecules called alkenones. Variation in the composition of these molecules, produced by algae, can serve as an indicator of atmospheric CO2. Isotopic proportions are also influenced by the growth rate of the algae, which is proportional to the available food and nutrients in the water. So the authors considered multiple scenarios to account for variations in nutrient availability, concluding that CO2 concentration increased by a factor of two to three during the MECO.

James Zachos, a professor of Earth and planetary sciences at the University of California, Santa Cruz, who specializes in the time period and methodology used the study, said in an e-mail to Scientific American that apart from what may be an overestimation of the mean partial pressure of CO2, and the magnitude of its rise, "the data look reasonable." The study adds value, he says, because "the application of multiple proxy records in one core to reconstruct climate is unique, at least for this time interval."

The MECO makes for a useful "historical laboratory," Houben says, within which climate dynamics can be studied over a much longer timescale compared with other historical warming events of interest to climate researchers. By investigating CO2 variations and temperature dynamics over longer periods, researchers can obtain a clearer understanding of the still partly unknown role played by long-term climate feedbacks, such as changes in the ocean's carbon chemistry and/or large-scale changes in vegetation.

Currently, climatologists have a much better understanding of the role short-term feedbacks, such as changes in water vapor or sea ice. Incidentally, there were no glaciers at the time of the MECO, so Hoeben's group could look exclusively at the relationship between CO2 and temperature without having to account for the fact that changes in the amount of sea ice can increase temperature, too. "We've shown that if you include those long-term factors, then CO2 might very well be the leading factor for temperature increase, especially in a world without a major ice sheet," Houben says.

The result, he says, will help climatologists get a better grip on the concept of climate sensitivity—the degree to which a global temperature increase is entirely dependent on an accompanying rise in CO2. The authors conclude that the climate sensitivity during the MECO led to a 2- to 5-degree C increase per doubling of atmospheric CO2.

The study does leave one big question outstanding: Where did all the MECO CO2 come from? This remains an area of speculation, Houben says, although scientists are fairly sure the source was not organic. However the CO2 got there, the takeaway from this study is simple: "In the past," Zachos says, "whenever atmospheric carbon dioxide levels rise, the climate warms."

http://www.scientifi...eric&print=true

[Obama 2012 1,714]

and of course, a tax will fix everything.

[I AM NOT THAT GUY 5,715]

James Zachos, a professor of Earth and planetary sciences at the University of California, Santa Cruz, who specializes in the time period and methodology used the study, said in an e-mail to Scientific American that apart from what may be an overestimation of the mean partial pressure of CO2, and the magnitude of its rise, "the data look reasonable." The study adds value, he says, because "the application of multiple proxy records in one core to reconstruct climate is unique, at least for this time interval."

We will see if other studies can replicate the findings.

[JohnSmith2007 353]

Those darn Eocene humans and their cars caused that one as well I bet. No adverse climate change can be natural you know, we always cause it. Did the Eocene congress pass a cap and tax to fix it?

[Danno 1,228]

and of course, a tax will fix everything.

Bingo!

YOu know how you know.... even steve doesn't worry about this stuff?

He and the rest of the Warming-crowd, all have big screen tv's Refrigerators and 1200 (or more) sq foot houses with A/C.

IF they can't give it up.... what chance do they have of making us give it up?

,,, and even if they could tax us into the pawnshop, the emerging third world is demanding all those nice things we enjoy.

[Ban Hammer 13,662]

Those darn Eocene humans and their cars caused that one as well I bet. No adverse climate change can be natural you know, we always cause it. Did the Eocene congress pass a cap and tax to fix it?

that's how they got rid of the neanderthals, they taxed them to death.

[one...two...tree 2,762]

Those darn Eocene humans and their cars caused that one as well I bet. No adverse climate change can be natural you know, we always cause it. Did the Eocene congress pass a cap and tax to fix it?

You should watch one of those science programs on public television sometime. They do a nice job of explaining these kinds of natural phenomenon. You are, however, making a straw man argument because the issue isn't that natural climate change can't happen, but the facts that one, atmospheric CO2 can tip the earth's temperature (something the denialists argue adamantly against, and two, that such changes in the earth's temperature happen GRADUALLY, over tens or even hundreds of thousands of years, giving living organisms a fighting change to adapt (evolution - another issue that denialists have trouble with).

The enormous amount of CO2 emissions, particularly over the last decade is tipping the earth's temperature at a much faster rate than has ever happened in the history of this planet. While denialists such as yourself ignorantly scoff at the notion that we humans drive living organisms to extinction, it is happening right now. It's too bad that you're already closer to the grave for you to finally see the consequences of such ignorance towards science.

[luckytxn 2,265]

Seeing as how the GW bunk scientists has lied and buried anything that didn't agree with them then I wonder what data they suppressed to even get this nonsense.

[JohnSmith2007 353]

You should watch one of those science programs on public television sometime. They do a nice job of explaining these kinds of natural phenomenon. You are, however, making a straw man argument because the issue isn't that natural climate change can't happen, but the facts that one, atmospheric CO2 can tip the earth's temperature (something the denialists argue adamantly against, and two, that such changes in the earth's temperature happen GRADUALLY, over tens or even hundreds of thousands of years, giving living organisms a fighting change to adapt (evolution - another issue that denialists have trouble with).

The enormous amount of CO2 emissions, particularly over the last decade is tipping the earth's temperature at a much faster rate than has ever happened in the history of this planet. While denialists such as yourself ignorantly scoff at the notion that we humans drive living organisms to extinction, it is happening right now. It's too bad that you're already closer to the grave for you to finally see the consequences of such ignorance towards science.

The "enormous amount of CO2"? Guess what, mans total output accounts for .001% of the total CO2 in our air. Yeah, really enormous. One good volcano dwarfs what we do. Keep your tin foil hat on, your going to need it now that your visions of a CO2 free world are over. Thank God for elections.

[luckytxn 2,265]

The "enormous amount of CO2"? Guess what, mans total output accounts for .001% of the total CO2 in our air. Yeah, really enormous. One good volcano dwarfs what we do. Keep your tin foil hat on, your going to need it now that your visions of a CO2 free world are over. Thank God for elections.

H2O is by far the largest greenhouse so maybe that is a better area to shoot for to reduce.

[Ban Hammer 13,662]

The "enormous amount of CO2"? Guess what, mans total output accounts for .001% of the total CO2 in our air. Yeah, really enormous. One good volcano dwarfs what we do. Keep your tin foil hat on, your going to need it now that your visions of a CO2 free world are over. Thank God for elections.

i guess now that elections are over, steven can't inundate us with party hack pieces, so global warming is full speed ahead.

[one...two...tree 2,762]

The "enormous amount of CO2"? Guess what, mans total output accounts for .001% of the total CO2 in our air. Yeah, really enormous. One good volcano dwarfs what we do. Keep your tin foil hat on, your going to need it now that your visions of a CO2 free world are over. Thank God for elections.

Says who?

[one...two...tree 2,762]

Man-Made CO2 As Seen Regionally From Space

While significant gaps remain in our total knowledge of the extent of carbon dioxide's sources, such as fires, volcanic activity and the respiration of living organisms, and its natural sinks, such as the land and ocean, it is known that more than 30 billion tons of extra carbon dioxide (CO2) is released into the atmosphere annually by human activities, mainly through the burning of fossil fuels.

.........

Using data from the SCIAMACHY instrument aboard ESA's Envisat environmental satellite, scientists have for the first time detected regionally elevated atmospheric carbon dioxide – the most important greenhouse gas that contributes to global warming – originating from manmade emissions.

This animation of carbon dioxide (CO2) shows how our planet 'breathes'. Each year huge amounts of CO2 are taken up by the growing vegetation in spring and summer and are to a large extent released again during the following autumn and winter when part of the vegetation dies and decays. This is seen in the animations by the up and down of the measured CO2 once per year. By looking carefully at the animation, it is possible to see that the CO2 levels are rising by about 0.5-1 percent from year to year. Dr. Michael Buchwitz and Oliver Schneising from the Institute of Environmental Physics (IUP) at the University of Bremen in Germany based produced this animation using Envisat SCIAMACHY observations from 2003 to 2005. Credits: IUP/IFE, Univ. Bremen

http://www.science20...ally_from_space

[luckytxn 2,265]

I wonder if scientists even know that CO2 is needed by plants. Also with all the volcanic activity throwing a lot more of CO2 in the atmosphere how do they tell what is man made and what is naturally. Also most know that a majority of scientists say that this is junk science and laugh at the attempt by governments to control the citizenry by this route.

The 300 ppm increase seen over decades is very insignificant. Here is the make up of CO2 before the 300 ppm, 4.0%. Here is the makeup when the 300 ppm is added, 4.0&. Get real people. The government thought they pulled a fast one on the gullible public to control us and have us pay a ####### load to their new green industries so those same industries will toss a portion their way. It also enabled them to pass laws to control us.

[Hilarious Clinton 452]

and of course, a tax will fix everything.

We need to build a time machine so we can impose a crippling tax on our ancestors.