Probing the past. Dark, red-brown ocean sediment layers reveal a telltale warming episode in cores retrieved by the drill ship JOIDES Resolution (inset).
Credit: J. C. Zachos; (inset) Integrated Ocean Drilling Program
Posted on 07/20/2009 12:26:26 AM PDT by neverdem
Probing the past. Dark, red-brown ocean sediment layers reveal a telltale warming episode in cores retrieved by the drill ship JOIDES Resolution (inset).
Credit: J. C. Zachos; (inset) Integrated Ocean Drilling Program
Carbon dioxide (CO2) gets a bad rep for contributing to global warming, and deservedly so. But scientists say they can't entirely blame the greenhouse gas for a curious spike in Earth's temperature 55 million years ago. New research reveals that something else also seems to have warmed the planet during that time, though no one's quite sure what it was.
Over the past couple of decades, researchers have been gathering data about a mysterious event known as the Paleocene-Eocene Thermal Maximum (PETM). The data, derived from drill cores brought up from the deep seabed in the Atlantic and Pacific Oceans, show that the surface temperature of the planet rose by as much as 9°C within 10,000 years during the PETM, which itself started out warmer than our current world. Temperatures stayed at this elevated level for nearly 100,000 years.
On the surface, the culprit appeared to be CO2. For reasons unknown, atmospheric concentrations of the gas rose by about 700 parts per million, from 1000 ppm to 1700 ppm--more than four times higher than today's level of 385 ppm--during the PETM. That much of an infusion of the well-established greenhouse gas should have been plenty to spike temperatures.
But a new analysis doesn't fully support this scenario. Oceanographer Richard Zeebe of the University of Hawaii, Manoa, and colleagues ran carbon-cycle simulations of the oceans and atmosphere based on the data yielded by the sediment cores. They even simulated what would happen to global temperatures when they increased the atmosphere's sensitivity to doubling CO2 levels--to 2000 ppm--during the PETM. The most they could achieve was a warming of 3.5°C, they report online this week in Nature Geoscience. That means some other phenomenon must have pushed up temperatures by as much as 5.5°C, the team says. So at present, the unexplained warming represents a gap in understanding about what causes significant and rapid climate change.
"It's possible that other greenhouse gases such as methane could have contributed to the [PETM] warming," Zeebe says. It's also possible that the models are underestimating the climate response to CO2 increases. If that's the case, it "would mean our understanding of the climate system is incomplete," he says.
Zeebe's team is now looking at smaller warming events that occurred within several million years after the PETM. "We're currently trying to find out whether or not [they] were caused by the same mechanism," he says. The idea is to determine whether the PETM warming was unique "or a universal feature."
Geochemist Gabriel Bowen of Purdue University in West Lafayette, Indiana, applauds the work. "We've long had a hunch that something was fishy about the climate response during the PETM," he says. "This study puts the nails in the coffin of the idea that climate during the PETM responded to CO2 alone." Says Bowen, "The urgent challenge now facing us is to find out what was amplifying [temperatures] during this event and understand what it means for Earth's future."
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FReepmail me if you want on or off my health and science ping list.
OR maybe they are over estimating the effects of co2, but perish the thought since ignorance only works in one direction.
These guys missed the memo?
The humanoid aliens from the distant planet Garbonski 3 shot a massive chunk, almost 1/3, of the asteroid belt into the sun just about that time. The resultant flares and hard radiation killed the inhabitants of Venus - the lizard people of Delton 16, the long-time enemy of the humanoid aliens. Today, the lizard people are long dead and gone, all trace destroyed by the now boiling surface of Venus.
The positive side effect was the eventual rise of humans.
I submit my theory is s provable as the CO2 theory currently proposed by these scientists.
I have come to the conclusion scientists are buffoons. No matter what happens, they think CO2 is the culprit. They are not thinking like scientists, but ideologs hellbent on promoting an agenda.
No kidding. That idea never once crosses their minds.
The Sun is much much bigger than the Earth.
Perhaps that has some of the cause....but of course that is harder to study with core samples...
That's the understatement of the decade!
So the earth had CO2 levels 5X today’s and temperatures 9 degrees hotter on average, and it survived? It also readjusted without any cap and trade laws. If that’s true, then what’s the whole climate crisis about? We don’t have to do anything. It’ll fix itself...or maybe the cooling will be a bigger problem. Ice ages aren’t nice to humans.
“I have come to the conclusion scientists are buffoons. No matter what happens, they think CO2 is the culprit. They are not thinking like scientists, but ideologs hellbent on promoting an agenda.”
While not as down on scientists as you (may be), I agree that there are those that pursue their ideology without thought.
I’m reminded of the glaciers that covered much of the northern US.
(AlGore hasn’t stated what the temperature goal needed is, has he?)
I recall a statue made of Asbestos at the NY Worlds Fair (from history, I wasn’t there). Of course, that ‘consensus’ about asbestos has changed.
I recall Nuclear energy portrayed as being so inexpensive that our meters would run backwards.
I recall that our oceans would provide all of the nutrition that we would need.
etc, etc.
Look up into the sky during the day. See that big glowing yellow ball in the sky? It's called "The Sun". It's a big ball of nuclear reactions that warm the planet. I suggest starting there.
I'm pretty sure it had been over ten times today's levels.
Most likely the increase in atmospheric was the result of the temperature increase, not the cause of it.
The amount of CO2 stored in the worlds oceans dwarfs the amount of CO2 in the atmosphere, by maybe as much a 1000 to 1, and the oceans would have gassed off huge quantities of CO2 as a result of the increase in temperature. Warmer temperature reduces the ability of water to hold dissolved gases, like CO2.
“We can’t tax what lived 55 million years ago but we can sure tax em now.”
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