Large methane release could cause abrupt climate change as happened 635 million years ago

May 28, 2008
Dolomite Cement
Dolomite cement, formed from oxidized methane as it evolved from melting methane hydrates at the end of the snowball Earth glaciation, present in wave-cut platforms at Marino Rocks, South Australia. The dolomite is orange-red and formed vertical plumbing of tubes and vugs as methane passed upward and disrupted overlying sediment. Credit: M. Kennedy, UC Riverside

An abrupt release of methane, a powerful greenhouse gas, about 635 million years ago from ice sheets that then extended to Earth’s low latitudes caused a dramatic shift in climate, triggering a series of events that resulted in global warming and effectively ended the last “snowball” ice age, a UC Riverside-led study reports.

The researchers posit that the methane was released gradually at first and then in abundance from clathrates – methane ice that forms and stabilizes beneath ice sheets under specific temperatures and pressures. When the ice sheets became unstable, they collapsed, releasing pressure on the clathrates which began to degas.

“Our findings document an abrupt and catastrophic means of global warming that abruptly led from a very cold, seemingly stable climate state to a very warm also stable climate state with no pause in between,” said Martin Kennedy, a professor of geology in the Department of Earth Sciences, who led the research team.

“This tells us about the mechanism, which exists, but is dormant today, as well as the rate of change,” he added. “What we now need to know is the sensitivity of the trigger: how much forcing does it take to move from one stable state to the other, and are we approaching something like that today with current carbon dioxide warming.”

Study results appear in the May 29 issue of Nature.

According to the study, methane clathrate destabilization acted as a runaway feedback to increased warming, and was the tipping point that ended the last snowball Earth. (The snowball Earth hypothesis posits that the Earth was covered from pole to pole in a thick sheet of ice for millions of years at a time.)

“Once methane was released at low latitudes from destabilization in front of ice sheets, warming caused other clathrates to destabilize because clathrates are held in a temperature-pressure balance of a few degrees,” Kennedy said. “But not all the Earth’s methane has been released as yet. These same methane clathrates are present today in the Arctic permafrost as well as below sea level at the continental margins of the ocean, and remain dormant until triggered by warming.

“This is a major concern because it’s possible that only a little warming can unleash this trapped methane. Unzippering the methane reservoir could potentially warm the Earth tens of degrees, and the mechanism could be geologically very rapid. Such a violent, zipper-like opening of the clathrates could have triggered a catastrophic climate and biogeochemical reorganization of the ocean and atmosphere around 635 million years ago.”

Today, the Earth’s permafrost extends from the poles to approximately 60 degrees latitude. But during the last snowball Earth, which lasted from 790 to 635 million years ago, conditions were cold enough to allow clathrates to extend all the way to the equator.

According to Kennedy, the abruptness of the glacial termination, changes in ancient ocean-chemistry, and unusual chemical deposits in the oceans that occurred during the snowball Earth ice age have been a curiosity and a challenge to climate scientists for many decades.

“The geologic deposits of this period are quite different from what we find in subsequent deglaciation,” he said. “Moreover, they immediately precede the first appearance of animals on earth, suggesting some kind of environmental link. Our methane hypothesis is capable also of accounting for this odd geological, geochemical and paleooceanographic record.”

Also called marsh gas, methane is a colorless, odorless gas. As a greenhouse gas, it is about 30 times more potent than carbon dioxide, and has largely been held responsible for a warming event that occurred about 55 million years ago, when average global temperatures rose by 4-8 degrees Celsius.

When released into the ocean-atmosphere system, methane reacts with oxygen to form carbon dioxide and can cause marine dysoxia, which kills oxygen-using animals, and has been proposed as an explanation for major oceanic extinctions.

“One way to look at the present human influence on global warming is that we are conducting a global-scale experiment with Earth’s climate system,” Kennedy said. “We are witnessing an unprecedented rate of warming, with little or no knowledge of what instabilities lurk in the climate system and how they can influence life on Earth. But much the same experiment has already been conducted 635 million years ago, and the outcome is preserved in the geologic record. We see that strong forcing on the climate, not unlike the current carbon dioxide forcing, results in the activation of latent controls in the climate system that, once initiated, change the climate to a wholly different state.”

As part of their research, Kennedy and his colleagues collected hundreds of marine sediment samples in South Australia for stable isotope analysis, an important tool used in climate reconstruction. At UCR, the researchers analyzed the samples and found the broadest range of oxygen isotopic variation ever reported from marine sediments that they attribute to melting waters in ice sheets as well as destabilization of clathrates by glacial meltwater.

Next in their research, Kennedy and his colleagues will work on estimating how much of the temperature change that occurred 635 million years ago was due solely to methane.

Source: University of California - Riverside

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plaasjaapie
2.2 / 5 (10) May 29, 2008
Isn't it fun how you always get some dollop of scientific reporting and inevitably get the pious littler sermon immediately following, viz,

%u201COne way to look at the present human influence on global warming is that we are conducting a global-scale experiment with Earth%u2019s climate system,%u201D Kennedy said.

Modernmystic
1.9 / 5 (9) May 29, 2008
Yeah apparently he forgot that there were no humans 65 million years ago, much less humans with CO2 producing technologies.

Is it out of the question that this might be a natural process after all given it's happened before without human beings around....nooooo that doesn't produce grant money.
D666
4 / 5 (7) May 29, 2008
Wow, are you ever able to miss the point. Several points really. First, the article is about a period 635 million years ago, not 65. But hey, you're only off by 3, right?
That's not a big deal except that it calls into question how much you actually read for comprehension. Secondly, the article is about how sudden changes in atmospheric composition can affect climate, and the conclusion (trivially obvious really) is yes, it can. Read the last sentence in the third-from-last paragraph (starts "We see that strong forcing...")

Your "point" seems to be that since it happened naturally once, it is completely impossible even in principle for it to be anything other than natural, ever. Based on what? Argument by sarcasm?
Modernmystic
2 / 5 (8) May 29, 2008
Nah my point is that since it happened naturally once it is completely possible for it to be happening naturally again...now.
userbob1
2.2 / 5 (6) May 29, 2008
In other words, researchers posit that the earth could abruptly fart! Pray it doesn't happen near a volcano!
rubberman
3.6 / 5 (5) May 29, 2008
How about pray it just doesn't happen again, since the last "fart" permanently changed the earths climate...albeit in a positive way as far as life is concerned. The next one could be as destructive as the last one was beneficial.
D666
3.4 / 5 (7) May 29, 2008
And *my* point (and the point of the article, and the point of GW predictions) is that the mechanism of climate change can be 'engaged' by natural processes (per this article) or by man-made processes. The argument of the deniers seems to be either A) CO2 isn't increasing, it's just your imagination, or B) Yes it's increasing, but it can't POSSIBLY have exactly the same effect as what has happened naturally numerous times in the past. Somehow the CO2 we're generating is 'good' CO2, I guess....
thales
2.2 / 5 (9) May 29, 2008
D666, I think these are straw man arguments. A) Nobody really is suggesting that CO2 isn't increasing, they're suggesting that the levels of human-generated CO2 are trivial, especially as compared to the greenhouse gases produced naturally (via, for example, volcanic eruptions and lightning-started forest fires). B) Of course it can have the same effect, but the degree to which we can affect this is questionable. I'd also like to point out that you hardly ever hear about the potentially positive effects of global warming. While it would no doubt have a detrimental effect on some life and would displace people -- well, doesn't life require change to adapt and evolve? And wouldn't large swaths of land too cold to use very productively (Alaska, Siberia) be newly available for more intensive development?

To summarize, it's not at all clear that humans can stop this change, and I think change is labeled "bad" too quickly.
D666
3.2 / 5 (6) May 29, 2008
No, it is very definitely not a straw man argument. *You personally* may not have made that particular argument, but that doesn't mean it isn't made. There has been every variation of CO2-denial, from "no increase" to "trivial increase" to "increase but no effect" and on up. And BTW the ACTUAL research shows that the levels of human-generated CO2 are anything but trivial. The actual increase in CO2 in the atmosphere is the largest and most abrupt in hundreds of thousands, if not millions of years. It's easy (well, relatively ease) to calculate the amount of CO2 injected by humans, given X cars, Y coal-fired generaing plants, etc. It's also easy to catalog the number of volcanoes etc happening around the world and calculate from that. The GW-denier argument that we don't *know* that CO2 is increasing -- well ok, we know that, but we don't *know* if it's increasing enough to make a difference -- well ok, we know that, but we don't *know* if it's going to make a significant difference to humanity -- well ok, it's looking based on previous events that it's going to be pretty catastrophic, but we don't *know* if we're actually contributing significantly... Well, yeah, we do know that. Sorry to disappoint.

And your point about having a detrimental effect on some people -- what you really mean is some OTHER people, don't you?

rubberman
2 / 5 (5) May 29, 2008
Nah, he's posting that from his flat in Kenya...
sams
2.2 / 5 (6) May 30, 2008
"I'd also like to point out that you hardly ever hear about the potentially positive effects of global warming."

That like suggesting that wars are good because they support the coffin industry. Even a few degrees change in average temperatures will devastate the environment. We do not live in a closed bubble - it would be a very bad outcome indeed for humans. Furthermore, the kind of change posed by a clathrate runnaway would be catastrophic to all life. I seriously doubt we would survive it.