Methane burps disproved? Gassy emissions no longer in suspect dock for melting the last ice age.

news@nature.com ^ | 9 February 2006 | Quirin Schiermeier

[neverdem]

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Published online: 9 February 2006; | doi:10.1038/news060206-9

Methane burps disproved?

Gassy emissions no longer in suspect dock for melting the last ice age.

Quirin Schiermeier

Strange ice: no evidence that melting methane triggered global warming after the last ice age.© Punchstock

Methane escaping from the sea floor to the atmosphere has been a popular suspect for causing rapid climate changes during and at the end of the last ice age. But new data derived from a Greenland ice core have delivered a killer blow to the idea.

Methane (CH₄) is a much stronger greenhouse gas than carbon dioxide. It is usually released from swamps or through biomass burning. But it is also trapped in huge amounts in some ocean-floor sediments, where it lies buried in a strange kind of ice known as 'methane clathrate'. These clathrates are stable only within a certain range of temperatures and pressures; when brought to the surface, they melt rapidly and release burnable gas to the air.

A catastrophic release of trillions of tonnes of methane is thought to have triggered a temperature jump some 55 million years ago in an already warm climate at the Palaeocene/Eocene boundary (see 'Gas leak!'). But some scientists suspect that similar methane bursts, triggered perhaps by submarine landslides, sea-level drops or changes in water temperature, may also have caused a number of rapid warming episodes during and at the end of the last glacial period.

The theory has been popularized as the 'clathrate gun hypothesis'¹. But now an isotope analysis of methane trapped in bubbles of a Greenland ice core seems to disprove the idea.

No sign of a burp

Todd Sowers, a palaeoceanographer at Pennsylvania State University in Philadelphia, measured hydrogen isotopes of atmospheric methane from three distinct warming episodes, 38,000, 14,500 and 11,500 years ago. Methane from clathrates contains more deuterium (the heavy form of hydrogen) than methane from land-based sources, thanks in part to the bacteria that create the gas on the sea floor, and the material they consume.

He found no evidence whatsoever in the data for increased amounts of methane from marine clathrates. "This means that seafloor methane reservoirs must have been stable at these times, or at least that no significant amounts of methane escaped the ocean," says Sowers, whose study is published in Science this week².

"The data are convincing," says Kai-Uwe Hinrichs, a geochemist at the University of Bremen in Germany. "They won't exactly increase the attractiveness of the clathrate gun hypothesis." At least for the three periods Sowell has looked at in high resolution, they may even be a "killer argument", adds Jerome Chappellaz, a geochemist at the CNRS Laboratory of Glaciology and Geophysics of the Environment in Grenoble, France.

Controversial killer

The clathrate gun hypothesis has been controversial from the onset. All Quaternary warming episodes seem to have been accompanied by increased abundance of atmospheric methane. But many climate scientists think this is an effect, rather than the trigger, of warming climates. In most cases, there is evidence that the methane values only began to rise several decades after the temperature started to climb.

None of this means that marine methane hydrates don't occasionally erupt, however. Hinrichs has used fossil remnants of bacteria that flourish only under high methane concentrations to show that large quantities of the gas must have been released in the Santa Barbara Basin off California during an event some 44,000 years ago³. This gas didn't necessarily escape to the atmosphere, he says, but it did come from underwater ice.

Researchers are now exploring the isotopic values of gas bubbles trapped in ice cores going back some 900,000 years, to find out where methane came from in the past.

How the world's methane hydrates will respond to future global warming and other disturbances is uncertain. Seafloor reservoirs currently contain twice as much methane as all known conventional fossil-fuel reserves. This makes them a target for the energy industry, but mining the gas could cause a runaway greenhouse effect, says Sowers.

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References

1. Kennett J. P.,

   Cannariato K. G.,

   Hendy I. L. &

   Behl R. J.

   American Geophysical Union, Special Publication,
   Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis.
   54, (2003).

2. Sowers T.

   Science, 311. 838 - 840 (2006).

3. Hinrichs K.U.,

   Hmelo L. &

   Sylva S.

   Science, 299 . 1214 - 1217 (2003).

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[demlosers]

It is usually released from swamps or through biomass burning.

[highlander_UW]

I thought this was going to be an article about democrat senators. Misleading title there.

[beyond the sea]

"Gassy emissions no longer in suspect dock for melting the last ice age"

****

Oh thank God for the gassy emissions. My wife (and I) will be relieved on our way out of the movie theatres.

[quantim]

Volcanos Helped Slow Ocean Warming  

Debris form a volcanic eruption that occurred more than a century ago still lingers in the Earth’s upper atmosphere where it is helping to keep ocean temperatures cool and offset sea-level rising, a new study finds.

Spewed ashes and aerosols from the 1883 Krakatoa volcanic eruption in Indonesia are helping to block sunlight and reduce ocean temperature warming.

===========

Good thing we have nature on our side.  ;-)

[308MBR]

Global warming is caused by the sun, you idiots.

[DannyTN]

Kennedy? Can you make Methane from pure alcohol?

[Outland]

"In most cases, there is evidence that the methane values only began to rise several decades after the temperature started to climb."

Interesting indeed. This cooincides with data that shows CO2 increases that followed temperature spikes. If CO2 nd CH4 are "potent" "greenhoue gases", then the reverse would be true.

It appears that temperatre rises probably accelerated the state of decay for dead vegetation which then released CO2 and CH4 (the bulk of CH4 and CO2 does come from vegetation decay). Again, this points to something else causing the temperature spikes.

Gee, folks... ya think it might be the Sun and increases in the main "greenhouse gas", water vapor???

[neverdem]

Good thing we have nature on our side. ;-)

Maybe nature, but Nature Magazine isn't, IMHO. Thanks for the pic and the link.

[gleeaikin]

One of the troubling results of Arctic warming is the melting of vast areas of permafrost in North America and Siberia. When frozen Co2 and other gases are sequestered. When it melts significant amounts of Co2, and presumably other gases are produced.

Another troubling result of Arctic warming is the melting in summer of the Arctic ice cap. It has been shown by recently released classified nuclear submarine data that around half the thickness of ice has melted in the past 30 years. Currently this ice reflects energy back from the earth. Once it is gone the ocean will absorb heat from the sun further accelarating the warming process.

[neverdem]

Again, this points to something else causing the temperature spikes.

How about Global Warming on Mars?

[neverdem]

Antidepressants may harm newborns' lungs

Drug ends spread of AIDS from mom to child

Biopsies Still Best Way To Find Breast Cancer

FReepmail me if you want on or off my health and science ping list.

[uglybiker]

The warming was caused by these guys.

[carumba]

But it is also trapped in huge amounts in some ocean-floor sediments, where it lies buried in a strange kind of ice known as 'methane clathrate'

Where is Velikovsky when you need him?

[Sir Francis Dashwood]

I am curious as to why the article did not mention that single greatest source of methane on the earth is termites...

[GOPJ]

Thanks for the ping.

[Wonder Warthog]

"Another troubling result of Arctic warming is the melting in summer of the Arctic ice cap. It has been shown by recently released classified nuclear submarine data that around half the thickness of ice has melted in the past 30 years. Currently this ice reflects energy back from the earth. Once it is gone the ocean will absorb heat from the sun further accelarating the warming process."

Disproven. The MOST recent data shows that the submarine data were wrong, and that the difference is due to normal migration of the ice masses. There's an article posted here in the last few days about it.

[YOUGOTIT]

"Another troubling result of Arctic warming is the melting in summer of the Arctic ice cap. It has been shown by recently released classified nuclear submarine data that around half the thickness of ice has melted in the past 30 years"

I thought I read that this was not a valid story and that the submarine data not correct?

[crghill]

I know a man who wrote a fiction novel about a massive methane hydrate release. In the book, it brought about masive destruction. It made for a good read, but I don't believe in man-made global warming. I'm old school, I still believe God is in control. Silly me!

[quantim]

This story needs a thread of it's own:

Volcanic eruption cut warming in 20th century

The 1883 eruption of Krakatoa—a volcano near the Indonesian island of Rakata—ejected more than six cubic miles (25 cubic kilometers) of rock, ash, and pumice and generated the loudest sound ever recorded by human beings. The tsunami that followed the eruption killed 36,417 people according to official records. The eruption destroyed two-thirds of the pre-existing island of Krakatoa and subsequent eruptions at the volcano since 1927 have built a new island, called Anak Krakatau. Anak Krakatau has since erupted on several occasions including the pictures eruption in 1992.

Eruptions regulate sea temperatures

The colossal eruption of Indonesia's Krakatau volcano in 1883 may have helped offset the effects of human-induced ocean warming, according to Lawrence Livermore Lab scientists.

Krakatoa's chilling effect

So what about volcanoes? Yes, they do release CO2 into the atmosphere, but they do more than that. When you take several million tons of rock and blow it into tiny little pieces, you end up with ash, and lots of it. So much, in fact, that along with breathtaking sunsets come severely affected climates. Following the huge eruption of Krakatoa in 1883, enough reflective volcanic aerosols were ejected into the atmosphere that the following year was known as the year without a summer.

Krakatoa helps to keep Earth cool

The explosion generated the loudest sound in human history, and was heard from more than 2,500 miles away.

According to a study published today in the journal Nature, the sulphate aerosols and a worldwide volcanic dust veil acted as a solar radiation filter, reducing the amount of sunlight reaching the surface of the earth.