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A new study by paleoecologist Margaret Fraiser at the University of Wisconsin, Milwaukee, offers an interesting new theory behind the cause of the Earth's largest extinction: copious carbon-dioxide

When most people hear the phrase "the earth's largest extinction", they think dinosaurs. 

Margaret Frasier knows better.  As a paleoecologist, she knows that the Earth's largest mass extinction of life occurred at the end of the Permian Period at the end of the Paleozoic Era; 252 million years before the first T-Rex ever walked the earth.  The extinction destroyed the large land amphibians' dominance of the land, and paved the way for dinosaurs to emerge as the dominant land species. 

University of Wisconsin-Milwaukee professor Margaret Frasier is studying this extinction avidly, looking for possible details to further our understandings of what might have caused this landmark event.

Her recent conclusions, published in an Elsevier journal [1] [2] (PDF) and detailed in a recent press release titled "When Bivalves Ruled the World," describe an Earth with run-away carbon dioxide levels.  She concludes that the Permian-Triassic mass-extinction was caused by toxic, oxygen-less oceans created by too much atmospheric carbon dioxide (CO2). 

The Permian-Triassic extinction event wiped out nearly 70 percent of species on land and 95 percent of sea species.

“Estimates of the CO2 in the atmosphere then were between six and 10 times greater than they are today,” Frasier states.  The largest continuous volcanic eruption on Earth – known as the “Siberian Traps” – had been pumping out CO2 for about a million years prior to the Permian-Triassic mass extinction.

Her hypothesis is that high CO2 levels at the close of the Permian Period caused global warming, greatly increasing global temperatures.  With no cold water at the poles, ocean circulation slowed, and the oceans were unable to mix with the little oxygen left in the air.

She cites a variety of evidence of high CO2 and low ocean oxygen levels in this fossil record.  One piece of evidence is darkened rock from underwater fossil strata of the time.  Darkening in ocean rock of this nature indicates a low amount of oxygen at the time of formation.

Frasier also collected evidence to support her theory in the form of bivalve fossils.  The only survivors of the extinction were bivalve mollusks and gastropods -- snails.  Only shallow water, tiny, small-shelled varieties with high metabolisms and a flat shape, which allowed them to spread out while feeding to extract more oxygen, survived.  Deeper water varieties, where there was less oxygen, and larger shelled varieties, which needed more oxygen, became extinct, disappearing from the fossil record.

A final piece of evidence cited is the disappearance of the coral reefs.  Coral reefs die if their environment lacks sufficient oxygen.

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By JackBeQuick on 9/1/2007 2:53:42 PM , Rating: 2
I glanced over the study. Does it say anywhere how high the CO2 levels were? Are we talking like 10x today's amounts or 5% more or what?

RE: Hmm
By JasonMick on 9/1/2007 3:28:14 PM , Rating: 2
Estimates of CO2 in the atmosphere are that they are 6x to 10x what they are today (from the press release source).

A good read to understand where we stand, if this study is correct, read:
an article from last year states:

"BBC News has learned the latest data shows CO2 levels now stand at 381 parts per million (ppm) - 100ppm above the pre-industrial average.
The research indicates that 2005 saw one of the largest increases on record - a rise of 2.6ppm"

2.6 ppm rise for 2005 is a 0.68% increase.

To get to the sort of state mentioned in the article, if CO2 rose linearly and taking the middle estimate of CO2 of 8x, it would take approximately, 1000 yrs. to reach this level.

Of course, the human population is growing still, so this trend is not linear, also many theories place warming as an exponential effect, self reinforcing over time.

Also, during this period in the Paleozoic, their were far less large land animals (like 6 billion humans) than there are today.

If the population growth increases and deforestation continues the CO2/O2 balance will shift farther, regardless of industrial production.

So I would say, if the current course of things does not change, you would see these kind of levels between 2107-2507.

I know thats a broad time range, but I want to avoid making faulty predictions.

Also, far before levels reach 8x, people would become seriously ill due to lack of O2 in the atmosphere. It would be like living at mountain altitude, today.

RE: Hmm
By Kuroyama on 9/1/2007 3:42:06 PM , Rating: 2
Reinforcing your point that CO2 levels are currently increasing quite rapidly, here's an interesting plot of CO2 levels taken from the much reported recent Antarctic ice cores:

Looks like the current spike seems to fit the historical pattern of a spike every 100,000 years or so (solar activity?), but (honestly) I'd be curious if Masher or someone else knows why the current spike is so much higher than other recent ones (which seem to peak around 280ppm).

RE: Hmm
By LogicallyGenius on 9/2/2007 9:33:09 AM , Rating: 1
I hope the oil barons don get her for this. Those mongers dont care a damn about anything as long as they can make money. Only a revolution that seizes natural resources form these capitalists moguls will change the situation. That dont mean i am a socialists either, owning natural resources = no more competition.

RE: Hmm
By masher2 on 9/1/2007 7:01:47 PM , Rating: 3
> "So I would say, if the current course of things does not change, you would see these kind of levels between 2107-2507"

Tsk, tsk. I'm going to have to call you on this. CO2 levels of 3,000ppm in only 100 years time? Was that a typo? Even the doomsayer IPCC using a "business as usual" scenario is only predicting a value of some one sixth as high. Even a prediction of 3,000 ppm in 500 years time is very pessimistic. One has to remember that anthropogenic CO2 is still only some 2.7% of total sources, which explains why even though human CO2 emissions have rising 10X in the past 60 years, the rate of increase of atmospheric CO2 increase has barely risen.

The Permian extinction event is the most mysterious of them all, and one that will be endlessly debated. Dozens of possible theories abound, including glaciation, nearby supernova, tectonic plate movement, poisoning from sulfate-based bacteria, and meteor impact:

Even if CO2 did play a factor it cannot have been-- as this author herself admits-- the only factor. During the Devonion, CO2 levels were twice as high as during the Permian-- over 7,000ppm. What happened to the biosphere then? Life thrived more than ever before in human history...the "Devonian Explosion" is the term for the huge increase in plant and animal biodiversity during the period.

So clearly CO2 cannot be the only factor, which is where the whole "methane gun" theory comes from. That vast methane deposits under the ocean-- coupled with huge amounts of CO2 and sulfur dioxide from volcanic eruptions, caused chemical changes in the oceans.

The other problem with the "runaway global warming" theory is that substantial sedimentary and glaciation evidence exists that the earth cooled during the Permian extinction event.

RE: Hmm
By JasonMick on 9/1/2007 7:49:22 PM , Rating: 2
Fair enough, on the first part, that bottom range is too pessimistic.

However, if you use your very own 10x increase per 60 yr., with the current human emission being 2.57 ppm incr. then you have the formula 2.57x10^((Year-2007)/60).

This yields a single year increase of 196,000 ppm in 2300. Now I believe your formula is slightly flawed, but it shows that my range could hold true. You gave those numbers yourself!

I agree that there are many possible explanations for this extinction. I even mentioned the meteor in my article.

And remember CO2 levels fell throughout the Silurian/Devonian. In the Devonian the seas dried up. The "explosion of life" referred to land life. The reason why land life could thrive is because CO2 levels had actually fallen since the Silurian and continued to fall during the Devonian.

While my bottom range might be flawed, your estimate of over 7000 ppm, is equally vague and flawed. First, what part of the Devonian are you referring to? The start, before the "greening of the land" by large tree like plants, the time period in which the oceans were drying up and sea creatures becoming extinct or being forced to come ashore to survive. Or the end, when CO2 levels had dropped substantially?? Also, I have never heard of a method to estimate the CO2 that far back, that precisely.

Actually the Devonian saw a major extinction as well:

The so called "explosion of life" was a forced evolution due to falling sea levels. It didn't necessarily mean that there was more life overall, just more life on land and more new species.

There was an "explosion of life" in the Triassic as well, remember, following this extinction.

Also, just wild conjecture, but if 70% of land species perished, wouldn't there be a lot less emitted CO2 and a lot more room for CO2 fixing plants to grow and flourish, free of predation? Just a thought, but this could easily explain why the Permian saw cooling as the extinction proceeded.

RE: Hmm
By masher2 on 9/1/2007 8:14:35 PM , Rating: 2
> "You gave those numbers yourself!"

Come, Jason, you're smarter than that. You cannot extrapolate exponential growth over any lengthy period. If nothing else, there just isn't anywhere near that much oil and coal to burn in the world.

All nations experience a rapid- but historically brief-- period of emissions growth...followed by a much longer period in which growth is slow. The US for instance at one brief point was doubling emissions every decade. But emissions over the last 20 years have increased far slower-- and in 2006, they actually declined slightly. Every other developed nation has followed the same pattern-- not only in fossil fuel use, but in other metrics as well.

Exponential growth cannot last, in any area. Look at the exponential increase in, say, aeronautical technology from 1915 to 1965. Then compare it to the utterly slow rate of advance in the following 50 years. Or look at the exponential growth in cultivated land in the US during the 19th century....whereas all throughout the 20th, that rate not only stopped, but went into reverse.

Trying to extrapolate the US growth rate in fossil fuel use during the 1940s over a period of several hundred years is just silly. You and I both know that.

> "Actually the Devonian saw a major extinction as well:"

Ah, but the Devonian event wasn't due to species extinction, but rather a simple decrease in the rate of speciation, stretching over several million years.

Yes, the most common theories for this are an impact event, or a reduction in CO2 levels due to

> "Also, just wild conjecture, but if 70% of land species perished, wouldn't there be a lot less emitted CO2..."

You're equating species extinction with reduction in biomass. Two different concepts. During many "extinction events", while the number of distinct species decreased, the actual raw number of plants and animals alive increased. (though this is not true for the Permian event, in which both species count and biomass decreased).

RE: Hmm
By JasonMick on 9/1/2007 9:16:42 PM , Rating: 2
Well, I was just using your own unqualified statement, if we are nitpicking. I appreciate that you find me intelligent, and I have remind you that I have said many times that exponential growth is unpredictable.

The key thing that would cause the current trends to increase/decrease is massive deforestation, combined with the collapse of the plankton ecosystem. The former is undeniably in progress, while the latter is likely to occur as the oceans become increasingly polluted with highly concentrated chemicals that were formerly in land based rock deposits.

I expect the levels of CO2 to level off in growth slightly with the decrease of emissions, then increase exponentially, as deforestation cripples the CO2 fixation system of the earth's biosphere.

Deforestation is the chief threat to global warming. Also overpopulation/livestock are a big threat, as well. Cows produce more CO2 than cars. The combination of more CO2 produced, less fixed, growing on both ends, is an exponential situation, which will continue to happen until we stop cutting down the forests AND the population stops growing. That is unlikely to happen for some time, I think you would agree. Its good that emissions are declining, but we have to still find solutions to these two major problems, I think you would agree.

Ah, but the Devonian event wasn't due to species extinction, but rather a simple decrease in the rate of speciation, stretching over several million years.

Did you read the linked article Michael? It states:

"A major extinction occurred at the boundary that marks the beginning of the last phase of the Devonian period, the Famennian faunal stage, (the Frasnian-Famennian boundary), about 364 million years ago, when nearly all of the fossil agnathan fishes suddenly disappeared...The most important group to be affected by this extinction event were the reef-builders of the great Devonian reef-systems, including the stromatoporoids, and the rugose and tabulate corals. The reef system collapse was so severe that major reef-building (effected by new families of carbonate-excreting organisms, the modern scleractinian corals) did not recover until the Mesozoic era."

Sounds like more than "decrease in the rate of speciation to me". In fact, this extinction, was among the five largest in history.

though this is not true for the Permian event, in which both species count and biomass decreased

So you are agreeing that the biomass decreased and my hypothesis could be possible??

Why put out an argument against my hypothesis based on facts you subsequently say were not true for the situation I am making the hypothesis for? That makes no sense. I was talking about the Permian, so my hypothesis, by your own admission remains a possibility.

RE: Hmm
By masher2 on 9/1/2007 10:04:10 PM , Rating: 3
> "Sounds like more than "decrease in the rate of speciation to me".

Paleobiologists disagree with you then. Let me quote:
Low origination contributed more than high extinction to the marked loss of diversity in the late Frasnian

In other words, the "extinction event" of the Late Devonian was driven primarily by new species failing to appear, rather than existing species disapearing. It was an event that took millions of years obviously.

And in any case, the CO2 levels during the late Devonian were falling rapidly, which makes your point doubly moot.

> " deforestation cripples the CO2 fixation system of the earth's biosphere."

Believe it or not, forests are a relatively minor portion of overall carbon fixation. A young, actively growing forest contributes a great deal...but old-growth forest (including rainforest) is a relatively static quantity, neither fixing nor releasing carbon in significant amounts.

In fact, recent research suggests that forests in the temperate zones may actually increase global warming. Their relatively minor contribution to carbon fixation being more than outweighed by the increased albedo they bring to the surface.

> "Why put out an argument against my hypothesis based on facts "

Because I'm not sure what your hypothesis is. I originally thought you were trying to link the Permian event to modern-day global warming, but you insist otherwise. So what exactly are you trying to suggest with all this?

RE: Hmm
By masher2 on 9/1/2007 7:05:58 PM , Rating: 3
> "Also, far before levels reach 8x, people would become seriously ill due to lack of O2 in the atmosphere."

Eh? This isn't correct at all. CO2 doesn't reduce atmospheric O2. It can potentially increase ocean acidity and circulation, which is theorized to reduce ocean O2.

If anything, increased CO2 will cause a (very) mild increase in atmospheric O2, due to increased biotic activity of surface flora.

RE: Hmm
By JasonMick on 9/1/2007 8:01:23 PM , Rating: 2
That statement does not make sense. Increasing ocean circulation would increase ocean O2.

Whether increasing CO2 decreases O2 depends on the cause of the CO2 incr, whether it was due to burning fossil fuels (fixed CO2) or because of increased deforestation/increased animal (human and livestock) population. The former would have the effect you mentioned, but the latter scenario, which I was referring to, which I find more concerning would actually cause a large decrease in atmospheric O2 over time, as plants could not keep up with animal demand.

I see population and deforestation as far more serious threats to producing global warming than industry.

As long as the rainforest, large land forest, and plankton--the great O2 producing CO2 sinks--stay alive, global warming CO2 increase can only be so bad, and O2 will be sufficient. But if these are destroyed due to human overpopulation and pollution, then you have a historical scenario never seen before since pre-Devonian, one where plant life can not respond to incr. CO2, because there is no large plant life left. O2 levels would fall and the earth could become uninhabitable to large land animals.

RE: Hmm
By masher2 on 9/1/2007 8:21:15 PM , Rating: 2
> "That statement does not make sense. Increasing ocean circulation would increase ocean O2."

Its not my theory, so don't ask me to support it. But it's supported by quite a few climatologists. Here's a link:

> "would actually cause a large decrease in atmospheric O2 over time, as plants could not keep up with animal demand."

Come Jason, do the math. CO2 levels are in the range of 300ppm. O2 levels are in the range of 210,000 ppm-- a thousand times higher. Historically, atmospheric oxygen has never varied substantially, not even when CO2 levels were 20X higher than current levels. There's just too darn oxygen in the air to be affected. The idea that any increase in CO2 levels could ever lower O2 enough to harm mankind is just plain silly.

> "I see population and deforestation as far more serious threats to producing global warming than industry."

Then you'll be pleased to know that the US actually has a higher level of forestation today than it did in the year 1900. Today, more of the US is covered in trees than was 100 years ago.

RE: Hmm
By JasonMick on 9/1/2007 9:32:53 PM , Rating: 2
Then you'll be pleased to know that the US actually has a higher level of forestation today than it did in the year 1900. Today, more of the US is covered in trees than was 100 years ago.

I am thrilled by that! I am happy to see those lazy environmentalist finally accomplished something!

However, the biggest forests, the Amazon, Congo, and Malaysian rainforest are being slashed and burned. While some will tell you that rainforests produce O2/consume CO2, this is only true respectively. Rainforests are a large, balanced systems. They do not have a net production of O2. However, if you replace these large areas with endless large cow plantations and towns, you are replacing a system in balance, with a CO2 producing system with virtually no CO2 fixing component. True they could plant crops, but the soil would fail after a few years, which is why they move on to slashing more forest. Meanwhile the human population remains behind.

Historically, atmospheric oxygen has never varied substantially

Has a single species ever systematically gone about clearing the earth of large portions of its largest biomass contributors, on a global scale?? I think we are dealing with a situation that has no historical precedent when it comes to man and its relationship with nature. Maybe there is not enough carbon to affect the O2 levels. The reaction would either be limited by carbon or o2, and I am guessing carbon would limit it. Still, over time, the CO2 levels would increase to levels not seen since the Silurian.

Ah, but I grow weary of this debate, as we could go back and forth on points like this all day, you know.

RE: Hmm
By masher2 on 9/1/2007 10:09:02 PM , Rating: 2
> "I am happy to see those lazy environmentalist finally accomplished something!"

Environmentalists had nothing to do with it. Increased forestation in the US is due to reclamation of previously cultivated farmland which, in turn, is due to the massive increases in agricultural output per acre since 1900.

In other words, we have more forests in the US today because we use fertilizers, pesticides, farm machinery, pesticides, and high-yield crops. We grow far more food on far less land. An achievement made possible only through use of fossil fuels.

> "Maybe there is not enough carbon to affect the O2 levels."

You're right, there isn't. O2 isn't CO2. There's far too much oxygen in the atmosphere to ever worry about reduced levels. Your previous point was incorrect, plain and simple.

RE: Hmm
By Ringold on 9/2/2007 1:59:02 PM , Rating: 2
I see population and deforestation as far more serious threats to producing global warming than industry.

It'd be nice if the environmentalists would update their litany of complaints at least once every couple decades.

Yes, in the 80s it might've looked like runaway population growth would swamp the world.

In the mean time, however, Europe has just not stopping growing but gone in to full retreat. Japan has lost a sizeable portion of its population. The United States grows only due to immigration and will likely join Europe in having below replacement level birth rates. Countries in Eastern Asia show the same pattern.

At the rate India and China are joining the developed world they, too, will stop growing eventually. Then it'll be Africa's turn. The last time I saw the matter discussed the top estimate for human population was a peak around 9 billion, followed by decline.

The era of exponential population growth is over and it's gone forever. While environmentalists cheer, economists now have less than half a century to figure out how to push politicians in the proper directions to avoid fiscal catastrophe, but that's a different issue. It's time to remove population growth from the litany of standard-issue complaints and boogey-men.

RE: Hmm
By Ringold on 9/2/2007 2:01:49 PM , Rating: 2
Oh, and another point about East Asia: I can't recall which country was offering it, but one of them offered a cruise to any married couple as a way to encourage couples to go off and have sex -- hopefully resulting in a child. These aren't exactly rich nations offering these expensive incentives. The times have changed.

RE: Hmm
By masher2 on 9/2/2007 2:06:17 PM , Rating: 2
Sounds like Russia. They've recently been offering larger and larger incentives to increase their birthrate. The birthrate is so low today that population is actually declining.

This is true for many other European nations as well. The only reasons their populations aren't shrinking is immigration from third world nations makes up the losses from their declining birthrate.

RE: Hmm
By Ringold on 9/2/2007 2:52:44 PM , Rating: 2
A few things I quickly came across to illustrate the situation:

Italy, especially, is only being held together by a flood of immigrants.

Japan I just plain remembered wrong; it's population hasn't lost any yet, but is near a peak, projected to drop (rapidly) from the current 128m to 95m by 2050, and 50-70m by 2100.

All of which throws a wrench in to the gears of the current welfare systems that rely on wealth transfers from the young to the old. In the Japanese example, the number of workers in their 20s is current 16m, but within 10 years that'll be a mere 3m -- and 81% decline. Schools and unverisities have all ready been merged and closed, making the impending population decline highly visible on the younger end.

I think it might've been Singapore that I recall hearing that from, but the internet is showing two things:
1) It's age -- it was from around 5-10 years ago, and thus is hard to find now.
2) Words to draw traffic for advertisements -- especially 'cruise vacation'.

At any rate, I'd be much more worried about depopulation rather than overpopulation.

RE: Hmm
By masher2 on 9/1/2007 7:53:50 PM , Rating: 2
I also want to point out that-- as scary as the phrase "mass extinction" sounds to the layman-- the process itself appears to have taken several million years. It was not in any shape any sort of "onvernight" dieoff.. It was simply a slow, but substantial decrease in biodiversity, spanning several thousand centuries.

Trying to link the event to modern-day fears of global warming is, albeit interesting, not very accurate.

RE: Hmm
By JasonMick on 9/1/2007 8:09:54 PM , Rating: 2
I didn't link it to modern day global warming. I clearly stated that the levels at the time were many times higher than those today. Read the article.

You are the only one who is linking this article to modern day global warming, Michael.

RE: Hmm
By masher2 on 9/1/2007 8:26:04 PM , Rating: 2
> "I didn't link it to modern day global warming"

So your first post to the thread, where you claimed we might be at levels similar to the Permian within the century was a slip of the pen? I saw that as fear-mongering.

If I misunderstood, and you're clearly saying that humans can in no way, shape, or form, trigger another Permian-style event-- then I retract that claim.

Glad to see you're not buying into the hype!

RE: Hmm
By JasonMick on 9/1/2007 9:46:08 PM , Rating: 2
The very first poster compared it to modern levels. I would have been happy to relegate this as a study on what might have happened in the past, without current context, if people had not asked, or began to debate about it.

And I do think humans, between population increases, livestock cultivation, and deforestation to make room for the former, can alter the carbon balance to be on the high side of what it once was in prehistory. Obviously the reaction will be limited by the amount of carbon, we can excrete into the air as CO2, once overpopulation has forced sufficient deforestation to give a net debt of CO2. From there on out it is just a matter of time to reach these levels. Maybe not in our lifetime. But certainly this could be happening in our grandchildren's lifetimes.

You try to distract people by mentioning industrial CO2 emissions, but you never explicitly refuse to refute the dangers of overpopulation and deforestation to the CO2 balance. I think thats because you understand that with time this could become a real threat.

I see a clear difference between trying to discuss a possible major danger to our habitat and "fearmongering" as you put it. I do apologize for putting the lower bound so soon. That was ill-thought out. You probably regret some of the hastier statements you have posted, as well, but I would not label you a "conflictmongering" person because of them. No one is infallible. The important thing, is that the discussion of this problem has merit, and you must as well, since you are sitting here typing verbose arguments against my statements.

RE: Hmm
By masher2 on 9/1/2007 10:30:02 PM , Rating: 2
> " but you never explicitly refuse to refute the dangers of overpopulation and deforestation to the CO2 balance"

Your views are 10 years out of date of modern climatology. Forests are not the large carbon sinks we once thought they were. The ocean itself, river transport, silicate/carbonate weathering, etc...these are the primary global carbon sinks.

There's more and more evidence accumulating that forest planting may actually decrease overall carbon fixation. Here's a link to get you started:

> "But certainly this could be happening in our grandchildren's lifetimes"

By even the most pessimistic of assumptions, we won't reach Permian-level CO2 levels for the next 500 years. The math here is indisputable. No matter what "tipping point" mechanisms one postulates, the carbon still has to come from somewhere. Even with massively disrupted fixation levels, there's still a hard limit on how much CO2 is generated annually.

RE: Hmm
By masher2 on 9/1/2007 10:40:48 PM , Rating: 2
> "2.6 ppm rise for 2005 is a 0.68% increase."

I wanted to respond to this separately. I don't blame you for not knowing this, because the media rarely reports anything but the most negative news-- but 2005 was a blip. The rate for 2006 dropped to 1.68. There's a huge amount of variability in the increase rate....In 1992, it was only 0.63, but 4 years earlier (when emissions were lower) it was four times higher-- 2.24. Clearly its driven more by natural factors than anthropogenic ones:

RE: Hmm
By rsmech on 9/1/2007 11:44:14 PM , Rating: 2
The largest continuous volcanic eruption on Earth – known as the “Siberian Traps” – had been pumping out CO2 for about a million years prior to the Permian-Triassic mass extinction.

Interesting article. I haven't read the link but I see the author is linking it to million years of volcanic activity. Maybe I'm wrong but I thought that a volcano releases a large amount of CO2. Where does this hypothesis lead you to make the connection that humans in maybe the last 200 years could equal or come close to 1 million years of volcanic activity, to even reach that amount in a fraction of the time.

Like I said I think it's interesting, but where is the link you are guessing to human activity?

RE: Hmm
By TomZ on 9/2/2007 12:27:49 PM , Rating: 2
The correlation with contemporary global warming is implied, not stated. This allows the author to let the majority of casual readers assume a connection, but then can deny he stated any connection when challenged by someone like you.

After all, what's the point of posting an article on CO2 and extinction if there wasn't currently a CO2 debate? I mean if the theory was related to O2 levels, this article wouldn't be of any interest.

Once they figure out that cars, factories, and human agricultural activities caused the high CO2 that caused the mass extinction, then I'll become interested. Otherwise, the discussion is completely academic.

RE: Hmm
By Kuroyama on 9/1/2007 3:29:11 PM , Rating: 2
Jason's posting says the CO2 level was between 6-10 times the current levels.

Certainly nothing we can do will match the CO2 emissions of 1,000,000 of Siberian volcanic eruptions. However, many posts here have in the past argued that CO2 levels are next to irrelevant. If 10 times our current CO2 levels can cause global catastrophic extinctions, it is still worth finding out what will happen from the smaller levels to which our current activities could contribute. (i.e. is this akin to saying that a bowlful of mercury will kill you and so will a few drops, or is it like a pure saccarine diet will give you cancer but is likely harmless in a cup of tea)

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