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Volcanic CO2 Caused Ancient Episodes of Global Warming

In order to predict our climate future, scientists spend a lot of time looking into the past, trying to understand what conditions were like during times when the planet was much warmer or much cooler than it is today. The latest instance: a report published in the February issue of the journal Geosphere, offering a plausible explanation for swings between long stretches of greenhouse warming and dramatic cooling over millions of years.

The culprit, said lead author Cin-Ty Lee of Rice University in an interview, appears to be the ebb and flow of eruptions from volcanic mountain chains around the globe, which alternately pump heat-trapping carbon dioxide into the atmosphere and allow it to be re-absorbed by rocks and living things.

While these changes happen far too slowly to have any bearing on the current, human-caused episode of global warming, they do help scientists to understand the relationship between carbon-dioxide concentrations in the atmosphere and global temperature changes.

The new idea is that it’s a more sustained series of eruptions from volcanoes in strategic locations along the edge of continents that cause these long periods of warmth. 
Credit: flickr/NASA’s Marshall Space Flight Center

The main effect of volcanoes in the modern world is to cool the planet by throwing particles of sulfur dioxide high into the stratosphere, where they temporarily block the Sun. In the distant past, however, paleo-climatologists have long believed that volcanic activity was a major cause of global warming. Massive eruptions — far more powerful than anything going on today — can pump large amounts of heat-trapping carbon dioxide into the air. The problem with that theory is that those events don’t last long enough to explain periods of warmer climate that have lasted tens of millions of years.

The new idea Lee and his colleagues are proposing is that it’s a more sustained series of eruptions from volcanoes in strategic locations along the edge of continents that cause these long periods of warmth. When they subside, the CO2 eventually drops, and the planet plunges into a colder period, with year-round ice deposits at the poles — the situation we’re in today.

The genesis of this idea was, Lee said, “kind of random.” About four years ago, he dropped by an informal weekly lunchtime seminar at Rice known as “Looney Noons,” in which scientists talk about works in progress and speculative theories rather than their more polished work. The talk that day was about a mass extinction that wiped out a big fraction of the planet’s species about 93 million years ago, and a light bulb went off. “I remembered learning as an undergrad years before,” he said, “that there was a lot of volcanic activity at that time in the Sierra Nevada” — a range which, like the Cascades and the Andes, is only intermittently volcanic today.

According to geologists volcanic mountain ranges were both more extensive and more active during period starting about 140 million years ago. 
Credit: flickr/NASA Goddard Space Flight Center

That led Lee and another colleague to think about the difference between volcano types, and particularly about the unique characteristics of volcanic ranges on the edges of continents. These are generally created when plate tectonics shoves a slab of the Earth’s oceanic crust under its continental crust. The oceanic crust melts and sends hot magma up through the continental crust, where huge amounts of carbon-bearing rock, mostly limestone and marble, lie. “These rocks are made up of about 40 percent carbon, so as the magma bubbles upward and dissolves that rock, it frees up an enormous amount of carbon that eventually reaches the atmosphere,” Lee said.

According to geologists, these volcanic mountain ranges, known as continental arcs, were both more extensive and more active during period starting about 140 million years ago, as the giant continent known as Pangea broke up into the continents we know today. As they drifted apart, the continents’ leading edges — western North and South America, eastern and southern Asia — plowed over oceanic crust, triggering an increase in carbon-rich eruptions. That finally waned about 50 million years ago, at about the time when the planet went through a gradual but inexorable cooling.

Lee said if this theory is correct, these continental-arc volcanoes would only have a warming effect if there were plenty of carbonate rock deposits on continental margins. And since these deposits come, in part, from the shells of living organisms that once lived on continental shelves, this could only have happened after evolution had produced those organisms in great numbers, which happened just a bit over 500 million years ago.

“This is very speculative,” Lee said, “but it may be that the presence of life on Earth has actually changed the impact volcanoes have on climate.”

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By Dave
on February 18th, 2013

“….it may be that the presence of life on Earth has actually changed the impact volcanoes have on climate.”

But now, in the Holocene, thanks to the genius of modern man there is a much faster and more efficient way to significantly alter the global climate.

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By Jan Freed (l.a./CA/90041)
on February 19th, 2013

Actually, Volcanoes cause climate cooling, not warming.  Why?  They emit smoke and other particles that block sunlight.  Mt. Pinatubo did that a few decades ago. In a graph of world average temperature the “fingerprint” of this is quite clear.

Also, volcanoes emit only a few per cent of the CO2 that we emit in burning fossil fuels.  Google that to be sure.

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By Dave (Basking Ridge, NJ 07920)
on February 19th, 2013


As you point out, it is apparently true that all of today’s active volcanoes (on land and at sea) emit net average amounts of CO2 which amount to in the region of 1% of anthropogenic CO2 levels (USGS data and that major modern day eruptions, as was for example the case with the Mt. Pinatubo eruption in 1991, can / did produce significant measurable short term – year or two - global cooling. So far I agree that you are correct. But, as supported by the work of many paleoclimatologists and other specialists, your conclusion is incorrect. This is why.

The residence time of CO2 in the atmosphere far exceeds that of ash and cooling aerosols thus providing a mechanism for a net long term warming impact of volcanic emissions. In the deep past there were no anthropogenic emissions of CO2 or other greenhouse gases and the natural carbon cycle was also necessarily quite different and varied. Nonetheless, volcanoes are typically and generally considered to have contributed to atmospheric CO2 and thence the atmospheric greenhouse effect by releasing subterranean CO2, some of which came/comes from the ‘burning’ of subducted carbonate rock. That is a pretty common thread in paleoclimatology.

The “speculative” premise reported here is that during a particular period in the deep past at about the time of the start of the breakup of the last supercontinent Pangea, significant quantities of volcanic CO2 may have been released from “continental-arcs” of volcanoes which at that time ‘fed’ on carbonate that was a rich biogenic carbonate sediment formed from the remains of sea creatures in those ancient continental shelves. And that those volcanoes were much more extensive and active than is the case today and hence they provided an important source of atmospheric CO2 via that mechanism. In turn, according to this, that would have produced an enhanced long term greenhouse effect keeping the planet extra warm for not just years but tens of millions of years during that particular distant time. Assuming of course that I read and interpreted it correctly…

It is interesting that today cement is manufactured by heating mined carbonate rocks in high temperature furnaces. The process turns the carbonate into an oxide and releases a significant amount of CO2 into the atmosphere – not unlike the way volcanoes do. Indeed cement, lime and magnesium oxide production contributes something like 5% as I understand it of total anthropogenic CO2 emissions and therefore by itself, that one industry exceeds the average CO2 emissions contributed to the atmosphere by all of the planet’s volcanoes.

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By Bernd
on February 20th, 2013

You mentioned cement, after your good explanation.

What about wild fires, which are global on the increase, also due to higher average temperatures?
Is carbon dioxide released into the atmosphere by wild fires having not a similar effect as volcano’s and cement? Never mind that after any kind of wild fires plant growth is better and partially that carbon dioxide is again absorbed. But is not more damage being done because of those wild fires?
Apart from this, I do not see a benefit of wild fires on larger and larger scales.

My point is, wild fires are human caused in approximate 95% of all occurring wild fires cases and cause huge amounts of CO2 into the atmosphere, depending on the ignited plants.
During wild fires there are between 10 (low grassland) and 1000 (tense jungle) tons of CO2 released into the atmosphere on each hectare of burnt land.
If I calculate as an average 80 to 100 tons CO2 per hectare burnt as an overall average (we can discuss if this is the appropriate average figure) and the 7 Million acres burnt last year in the US, this would be about 2,8 Million hectares.

The 2,8 Million multiplied by 80 or 100 equals 224.000.000 tons of CO2 (280 Million tons) into the atmosphere, only in the US!
I don’t even calculate the 5% from natural occurrences, because I neglect it.

This CO2 released from wild fires into the atmosphere would be equivalent with about 60-70 Millions cars each year, if each of those car travels about 20.000 kilometres.

Now, I can see in general a need and use for cars and cement, but I cant see a need and use for wild fires!

Don’t understand me wrong, I see the carbon outputs on cement, cars, coal power stations and so on, there must be much more done to reduce everything, but I cant see any need on wild fires, which cause human harm (death), human health issues and cost and those which are financially through it affected (e.g. burnt houses).

We cant do much about volcano’s eruptions, but we can learn from it, as the article suggests.
Should we all not fight wild fires much more than presently that only these 5% natural wild fires are left?

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By Dave (Basking Ridge, NJ 07920)
on February 20th, 2013

Hi Bernd:

You asked so I will tell you how I see it.

All the life, meaning all the plants and so on is all generating CO2 by respiration and much of the natural world is using or recycling that CO2 via photosynthesis. Those amounts (emitted and consumed) are in fact far greater in magnitude than what man is generating. However, that is all part of the natural cycle which in an ideal world when you add up all the bits – the sources and sinks - is approximately in balance so that the CO2 concentration and other GHG’s in the air due to those processes alone remain about the same.

Same thing with the wood in trees; that carbon was sequestered from the atmosphere via photosynthesis. In the ideal balanced world if some of the carbon in the wood and other plant matter, eventually decays or gets burnt in a natural fire and the carbon dioxide arising from that finds its way back into the atmosphere at some balanced rate that approximately matches the rate of new growth then there should be no net long term harm.

But the carbon ‘cycle’ with man around is decidedly not in balance. The CO2 concentration is unnaturally high and increasing, due mainly to the tens of billions of tons per year of anthropogenic emissions from burning fossil fuels etc which are mined out of the ground. In this unnatural or anthropogenic case, the natural world cannot keep the CO2 in balance anymore by making new fossil fuel deposits at the same rate as they are being consumed – meaning all the gas, the coal and the oil – and that also applies to the carbon locked up in the carbonate rocks used to make cement. Man is consuming in decades what took millions of years for natural processes to create.

So there’s the imbalance and the predicament and the reason for the push to develop more renewable energy sources like wind and solar and generally try to provide options so that human society can progress from a smokestack world to becoming carbon neutral. Of course, we also need construction materials like concrete. So this imperative necessarily extends to those types of materials as well. Last year I happened to become aware of some advanced materials research that came out of Rutgers here in NJ aimed at creating carbon neutral construction materials that could potentially also replace concrete and be cost effective. I’m sure there are other projects and that that is just one example. The point is that we need to foster the R&D infrastructure too to help facilitate all these types of solutions.

But, the question you pose about fire control in forests requires input from one or more specialists in that area. I have heard like you and can understand that smaller fires once in a while keep a forest healthy in the long run. They tend to remove dead wood, dry brush etc that might otherwise accumulate and eventually fuel a more devastating fire later. That makes sense to me. But, the extensive wildfires in this country last year and that made the TV news for so long went well beyond that. So to your point, and aside from all the other important issues to do with that, those wildfires must also have consumed an unusually high number of large healthy trees. I don’t know that statistic. Whatever it is, they will take a while to replace. Ideally any impact on the atmospheric CO2 concentration due to those events will be short term provided that we are able to properly restore and maintain the forests.

I guess for me the questions about that are then how to manage forests effectively in the longer term in a changing climate.  And in the short term, what is the current state of the forests across the country?  And, are we headed for more of those types of wildfires in certain regions again next year, especially if the drought continues?

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By Bernd
on February 22nd, 2013

Thanks Dave, for your comprehensive answer.

As you have pointed out, there are other solutions to cement, as well as, petrol driven transport or the present energy types consumed.

I can not compare the size of the US with e.g. Germany, but there are less than 500 hectares of wild fires in average annually, despite getting warmer there as well and quite a while ago in some disaster years, there have been some bigger wild fires.
But as you pointed out, in the forest management seems to be the answer, it is also more effective in Germany, otherwise there would be a similar scaled increase.
On the other side, in the Mediterranean countries, wild fires are on the increase and land management surly got worse in those states.


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By Dave (Basking Ridge, NJ 07920)
on February 22nd, 2013


Thanks for the perspective. Each country has its own needs and goals. Hopefully some people learn from those different experiences so as to make fewer mistakes. Ordinary people enjoy the fact that there are forests, national parks and wild open land. Commercial interests compete with that. Environmentalists fight for the sake of the natural beauty, biodiversity, habitats, carbon absorption and so on and the push and pull goes on. Somehow, so far the forests and parks remain. They are extensive, varied, often amazing and need to be maintained as a national resource here as in your country. I think the wildfires here last year raised awareness. No one wants to see that again.

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By t rocks
on March 2nd, 2013

you both happily accept the usgs data without considering their very questionable methods of estimating.  the usgs have a personal interest in the climate debate because they stand to have many more jobs and greater importance and pay if the govt gets fully into the very questionable area of moderating the earth’s temp via co2 restrictions and exchanges.  in short the usgs data you cite was disproven by real scientists without personal profit motives and in fact the only reason the usgs paper even EXISTED was to support the idea of man made solutions to earth’s temp variations.  the weatherman cannot accurately predict the next two days in any city but san diego but we should believe the climate predictors that see oceans rising a hundred feet and the death of living creatures???  i sure as heck will not listen to those fools.  the more likely scenario is changes and fluctuations over the next 20000 years that do not render earth uninhabitable but that require some adjustments, just as humans have had to adjust over the last 20000 years.

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By Ralph Prater
on December 13th, 2013

What effect to Climate change does a weaken magnetosphere have to global warming and volcanic eruption?

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