Venus Syndrome Possibility

[fishmahboi]

As everyone knows recent Climate Change extremes have brought about some severe consequences with regards the increases in severe storms, flooding and drought which have had detrimental effects on infrastructure and the production of crops with the likely worst case scenario to be an increase in the depth of the sea and starvation.

However one consequence that dwarfs even the worst climactic threats is that of the Venus Syndrome which refers to the Runaway Greenhouse Effect that turned Venus into a planet that has a temperature that puts Mercury's temperature to shame.

With regards its effect on earth it is possible to disregard it as a risk as it does not have go get this bad for the outlook to be shown on a catastrophic level, however the chances of it happening on earth have interested me as there have been record Methane increases in the Arctic (http://arctic-news.blogspot.ie/2013/03/record-methane-in-arctic-early-march-2013.html), the existence of the potential for a sudden release of Methane from the Methane hydrates that are present in the Arctic Permafrost and beneath the Arctic Ice Pack along with the reduction in Greenland's Albedo and the fact that man has continued to utilize Carbon Dioxide regardless of the threats posed by climate change.

The reason for the creation of this thread was that I was interested to hear your opinion on the possibility of Venus Syndrome happening on Earth.

I am neutral with regards this because I know very little about Climate Change in general.

[gfwellman]

The short answer is "no", or "not for a few billion years until the sun gets hotter."

AGW is serious and could render large parts of the earth useless for people.  But we don't need to worry about a Venus style runaway.

[birthmark]

I agree with gfwellman completely.

[Dromicosuchus]

Likewise.  In a worst-case scenario in which all the ice melted, the clathrates and permafrost thawed, and mass desertification took place (releasing CO2 into the atmosphere from mass vegetation dieoffs), any remaining positive feedbacks would be fairly small--and as similarly massive warming events in the past (the PETM and the Great Dying come to mind) didn't lead to Venusification ("Venerification?"), I doubt very much that the feedbacks currently in place on Earth would be able to do the deed. 

[Glenn Tamblyn]

fishmahboi

My understanding of the analysis done by various scientists is that a runaway to a Venus like scenario is virtually impossible at this point in Earth's history. Warming to levels that are disastrous for humanity is definitely possible but Venus, no.

An important thing to understand about positive feedback situations in any context, not just climate, is that they don't automatically lead to a runaway. A positive feed back needs to not only increase the value being considered, the increase needs to lead to an ever increasing positive feedback to cause a runaway. A feedback that, while positive, declines as the value grows will not cause a runaway.

As an example, albedo change due to ice melt. This is a positive feedback. But as the ice melts the size of the feedback falls as the remaining ice area contracts to zero. Eventually ice melt supplies no feedback because there is no ice left to melt.

Fast forward 500 million years, when the Sun has warmed around 3%, and reductions in CO2 levels in the atmosphere can no longer compensate for this and it is a different scenario. Then a Venus does happen. Life on Earth has 500 million years left.

[Shared Humanity]

I am also optimistic that earth will not suffer such a fate. I think that earth's abundant atmosphere and water causes the planet to be more resilient and able to bounce back from dramatic warming events. There is actual evidence in the geological record to support this but it is not necessarily good news for humans.

250 million years ago there was a dramatic warming on earth. Geologists have been able to prove that CO2 and methane levels rose catastrophically. They've finally been able to identify the triggering event, a huge volcanic eruption in Siberia (the Siberian traps) This flood basalt eruption lasted 1 million years.

http://palaeo.gly.bris.ac.uk/palaeofiles/permian/siberiantraps.html

The warming was so severe that it resulted in the extinction of between 90% and 95% of all life forms. This extinction event was far more severe than the one that wiped out the dinosaurs 65 million years ago. The fossil records even have served to explain how the extinction event played out. The initial impact of the eruption was to kill a substantial portion of plant life due to a rapid cooling (volcanic winter). This extinction of plants occurred on both land and sea. The CO2 uptake was reduced and CO2 levels began to rise followed by a huge increase of methane as methane clathrate thawed. The rapidly rising temperatures due to the greenhouse effect caused a 2nd major extinction on land and sea. We may take some comfort in knowing the entire extinction event took 80,000 years.

This doesn't mean this is our fate but it does show that runaway global warming can happen.

[fishmahboi]

I am also optimistic that earth will not suffer such a fate. I think that earth's abundant atmosphere and water causes the planet to be more resilient and able to bounce back from dramatic warming events. There is actual evidence in the geological record to support this but it is not necessarily good news for humans.

250 million years ago there was a dramatic warming on earth. Geologists have been able to prove that CO2 and methane levels rose catastrophically. They've finally been able to identify the triggering event, a huge volcanic eruption in Siberia (the Siberian traps) This flood basalt eruption lasted 1 million years.

http://palaeo.gly.bris.ac.uk/palaeofiles/permian/siberiantraps.html

The warming was so severe that it resulted in the extinction of between 90% and 95% of all life forms. This extinction event was far more severe than the one that wiped out the dinosaurs 65 million years ago. The fossil records even have served to explain how the extinction event played out. The initial impact of the eruption was to kill a substantial portion of plant life due to a rapid cooling (volcanic winter). This extinction of plants occurred on both land and sea. The CO2 uptake was reduced and CO2 levels began to rise followed by a huge increase of methane as methane clathrate thawed. The rapidly rising temperatures due to the greenhouse effect caused a 2nd major extinction on land and sea. We may take some comfort in knowing the entire extinction event took 80,000 years.

This doesn't mean this is our fate but it does show that runaway global warming can happen.

I would like to point out a blog article that states that the abrupt warming that could occur as a result of a large scale methane release and other feedbacks in modern times could be unique to the earth.

The reason for this is that according to the article, the amount of stored methane was much lower than the amount that we can see today.

http://arctic-news.blogspot.ie/2013/03/tipping-points.html

Now, Earths vulnerable Carbon stores are:

Carbon in the Arctic

ESAS:
500 Gton C organic
1000 Gton C hydrate
700 Gton C free methane
total: 2200 Gton C

+other submarine arctic permafrost:
2200/0.8=2750 Gton C

+1700Gt in land permafrost= 4450 Gton C

A large part of this is Vunerable to being lost rapidly into the Ocean/Atmosphere system if the Arctic defrosts, polar ocean warms, heavy rainfalls hit the Tundras.

Carbon in soils and Living Biomass:

Total organic C in soil and living biomass is approx: 1000 Gton C living + 1500 Gton soil.

= 2500Gton C

A large part of this is Vunerable to being lost rapidly into the Ocean/Atmosphere system if the Arctic defrosts, Global weather systems change, Rainforests and/or peat deposits burn, desertification and/or heavy rainfalls hit the Tropical, Temperate, Boreal forests.

So thats the vunerable surface Carbon stores. Total about 7000 billion tons of carbon.

There's never been this much in the history of planet earth, that we know of.

Carbon in Deep sea Clathrates:

estimates range from 5000 Gton C to 78000 Gton C

A large part of this is Vunerable to being lost into the Ocean/Atmosphere system if the oceans warm a few degrees, reaching the bottom in a few hundred to a few thousand years, causing the stability to be lost.

There's never been this much in the history of planet Earth, that we know of.

Another article also points out the lack of methane in the Arctic during previous extinction periods.

http://arctic-news.blogspot.ie/2013/03/the-worst-case-and-unfortunately-looking-almost-certain-to-happen-scenario.html

The previous anoxic supergreenhouse/anoxic ocean events did have stalled ocean circulation, and the only way that they could have had 27C polar ocean temps like they did is by the Equatorial-Polar jetstream circulation mode described above.
The most serious previously, the end-permian had no polar basin, oceanic/ atmosphere circulation, turbine pump "beartrap" for the planetary eco-geosphere to put its foot in. Neither did the PETM and Elmo supergreenhouse/anoxic ocean events, the most serious of the last 100+ million years, the polar basin was landlocked for those.
Never before could the earth have had as much polar permafrost methane and carbon as it does now.

[ChrisReynolds]

I too had thought it impossible. I still think it so unlikely it's not worth worrying about. But this article suggests there's research which shows it is not feasible with the current understanding of physics, but that poorly understood issues like clouds could be the 'get out clause' that makes a runaway GHG effect feasible.
http://www.technologyreview.com/view/426608/how-likely-is-a-runaway-greenhouse-effect-on-earth/

To quote from the abstract of the source paper:

The good news is that almost all lines of evidence lead us to believe that is unlikely to be possible, even in principle, to trigger full a runaway greenhouse by addition of non-condensible greenhouse gases such as carbon dioxide to the atmosphere. However, our understanding of the dynamics, thermodynamics, radiative transfer and cloud physics of hot and steamy atmospheres is weak. We cannot therefore completely rule out the possibility that human actions might cause a transition, if not to full runaway, then at least to a much warmer climate state than the present one.

Source paper:
http://rsta.royalsocietypublishing.org/content/370/1974/4197.short

As I can't spare the time for all the sea ice stuff I'm behind on, I definitely can't spare the time to delve into this matter properly.

[fishmahboi]

I too had thought it impossible. I still think it so unlikely it's not worth worrying about. But this article suggests there's research which shows it is not feasible with the current understanding of physics, but that poorly understood issues like clouds could be the 'get out clause' that makes a runaway GHG effect feasible.
http://www.technologyreview.com/view/426608/how-likely-is-a-runaway-greenhouse-effect-on-earth/

To quote from the abstract of the source paper:

The good news is that almost all lines of evidence lead us to believe that is unlikely to be possible, even in principle, to trigger full a runaway greenhouse by addition of non-condensible greenhouse gases such as carbon dioxide to the atmosphere. However, our understanding of the dynamics, thermodynamics, radiative transfer and cloud physics of hot and steamy atmospheres is weak. We cannot therefore completely rule out the possibility that human actions might cause a transition, if not to full runaway, then at least to a much warmer climate state than the present one.

Source paper:
http://rsta.royalsocietypublishing.org/content/370/1974/4197.short

As I can't spare the time for all the sea ice stuff I'm behind on, I definitely can't spare the time to delve into this matter properly.

The lack of knowledge that allows one to state that a Venus Syndrome scenario is unlikely to occur on the earth is somewhat worrying at this point now that a combination of feedbacks can occur this coming summer ranging from the loss of albedo as a result of the Arctic Ice Pack disappearing and the inevitable thawing of the Methane Hydrates and Permafrost.

[Pmt111500]

Personally, I'll start to worry about Venus syndrome when the ozone layer is completely destroyed to let the UV fully to warm the surface, when methane saturated water vapor clouds reach the stratopause, and some evil syndicate ejects 100*current levels of additional CFCs (chlorofluorocarbons) to stratosphere to block the remaining outgoing radiation atmospheric spectral windows. Of course by then I've died many times over due the lack of food, 50 degree surface waters of oceans, and the deoxygenation of the troposphere due plant dieback.

Perhaps this could be a plot for an Austin Powers movie.

Background:
Venus
http://upload.wikimedia.org/wikipedia/commons/d/df/AtmosphereofVenus.svg
http://upload.wikimedia.org/wikipedia/commons/6/63/Venusatmosphere.svg
Earth:
http://upload.wikimedia.org/wikipedia/commons/7/7a/Atmosphere_gas_proportions.svg
http://upload.wikimedia.org/wikipedia/commons/9/9d/Comparison_US_standard_atmosphere_1962.svg

And this not even taking into account the pressure difference (Venus' atmosphere 92*thicker than Earth's)

[Anonymouse]

@ Shared Humanity (post #5), with all due respect, knowing that "the entire extinction event took 80,000 years," 250 million years ago tends to lend me LESS comfort, as some of the changes, such as the recent shattering of the Arctic ice, are happening all within my lifetime.
 
Doesn't the whole message about climate change boil down to the fact that slow change is normal, but the kind of extremely fast changes we seem to be witnessing are absolutely, unequivocally, ABNORMAL?  I think that the analogy of humans as similar to a huge asteroid strike problematic, but very apt.  Trouble is, it is not a very palatable story to tell.  And I am not sure that we could not enter into runaway in less time than a few hundred or thousand years. Things are happening too fast now, and we have no clue about the extent of positive feedbacks.A survey of the past 11,000 years is great, it is very normal, very calm and collected.  A survey of the past 200, past 50, and for heaven's sake, the past 10? Wonderful as well.  Unnerving to the extreme as to results, however. 

I GET it - we need to keep calm and observe on, but it is causing me to bite my nails. I am part of what Anthony Leiserowitz (Bill Moyers - http://billmoyers.com/segment/anthony-leiserowitz-on-making-people-care-about-climate-change/ ) calls the "16%" - alarmed, but paralyzed. I have been for many years now.  HotHouse Earth, indeed.

Note to Neven, because I am sure you have absolutely nothing else to do these days but tinker with the forum , I would like to suggest a format where comments are listed in numerical order, a la RealClimate.  This might make it easier to reply to specific posts. 
EDIT: WHOOPS never mind, I missed it. Thanks in advance.  My reply was to #5.

[Glenn Tamblyn]

To sum up perhaps

Abrupt changes to significantly different climates - quite possible.
Climate Changes that are disastrous for humanity and human civilization - quite possible.
Climate changes that lead to a major mass extinction event - quite possible.
Climate changes that wipe out all life on Earth - virtually unimaginable. You don't kill ALL the bacteria that easily, they exist down to depths of 5 kilometers and more inside the Earth's crust. So evolution can restart.
Runaway Greenhouse, also virtually unimaginable.

[Anonymouse]

Glenn #11,
I am not sure anyone is saying a TOTAL extinction event, but for humans, oh yes that is possible probable.  Cockroaches and bacteria?  I, for one, welcome our new insect overlords!

NEVEN,  Thanks again for this great forum.  All of us lurkers are crawling out of the baseboards now and making your life miserable, I am sure.  Keep up the great work, you and the regulars probably do not realize how important you are to us irregulars.  We are out here, and very worried, but only have the feels to go on, and no little to none of the scientific training you all have on the subject of our global refrigerator.
May your student loans be paid in full,
Anonymouse

[dorlomin]

The hotter it gets the more rock weathering we get. Rock weathering increases the rate of CO2 sequestration.  Above 3C  the climate sensitivity drops again as the ice is no longer able to give a feedback.





As the oceans temperature climbs and its stratifies it becomes anoxic, this also becomes a sequestration mechanism. Biomatter falling to the bottom does not decompose and this draws carbon from the atmosphere. This mechanism has worked in two previous anoxic ocean events (IIRC the mid Jurassic the lower Cretaceous), both of these are associated with flood basalt events. The irony of ironies…. These two events are where the deep rich beds of biomatter were accumulated that when buried were transformed into our oil and gas reserves. Much of our current fossil fuels comes from the sequestering of ancient super greenhouses [70% of oil source rock is mesozoic].

[Anonymouse]

Hi Dorlomim #13,
Do you have any underlying formula or data for all of these claims? Mark my words, I am not saying they are false, but I am asking why you bring them up?  What is the time scale for these events you list? How are they relevant?  Citations to peer reviewed data are, of course, important to your answer.  I await them with bated breath, because it sounds like you are implying that you are able to lay the foundations for some mysterious mechanism that will disprove the theory of AGW. (Tick tock....) But don't forget, I am an idiot mouse.

The hotter it gets the more rock weathering we get. Rock weathering increases the rate of CO2 sequestration.  Above 3C  the climate sensitivity drops again as the ice is no longer able to give a feedback.


ETC ETC ETC ETC

[dorlomin]

I await them with bated breath, because it sounds like you are implying that you are able to lay the foundations for some mysterious mechanism that will disprove the theory of AGW. (Tick tock....)

We teach rock weathering to 10 year olds here in the UK
http://www.bbc.co.uk/bitesize/ks3/science/environment_earth_universe/rock_cycle/revision/8/

[Anonymouse]

Hi Dorlomin #15,
Yes, I get rock weathering.  I am feeling very trollish today, sorry for any hurt feelings.  But I guess I am not getting where you are going with the earth history.  I am pretty sure that anyone reading this is at least familiar (if not an expert) with the basics of the origins of fossil fuels.
EDIT : My peeve is regarding timescale.  I am very concern-troll regarding the timescale of this stuff.  Recently - say the last 15 years - I have become very peevish on the issue of climate change, so please forgive my shortness and lack of comprehensive minutae.

[Shared Humanity]

@ Shared Humanity (post #5), with all due respect, knowing that "the entire extinction event took 80,000 years," 250 million years ago tends to lend me LESS comfort, as some of the changes, such as the recent shattering of the Arctic ice, are happening all within my lifetime.

Hi, Anonymouse......I guess I was not as clear as I wanted to be and my sense of the ironic did not come through. I believe we are speeding towards a disaster. I am not certain we can now avoid a runaway greenhouse effect. The effect might not be as severe as the Permian extinction event which wiped out maybe 98% of all life on the planet but it will be a large extinction event which will be far more destructive of large life forms than say, bacteria. Mammals will be decimated. Will humans avoid this fate? I'm not sure. We will certainly last longer then the elephant or other majestic mammals. Our technology will allow us to, perhaps, burrow underground. If we do survive (I have my doubts due to the simple fact that we are so dependent on this complex web of life which we generally ignore at our own risk.) there will be far fewer of us.

My optimism about a Venus type end result rests in the way the planet rebounded from this Permian extinction event which was triggered by the million year long Siberian traps volcanic activity. All life was not extinguished. The experiment with life on this planet will continue. It will take tens of millions of years for life to rebound. Hopefully, earth will have learned a lesson and avoid previous mistakes with this experiment. Clearly, intelligent (?) life forms can be destructive. Either avoid that altogether or get them smarter, faster. (Perhaps just don't give them thumbs.)

I feel good that while we are delivering an amazing gut punch to mother earth, she can take it. Our (humanity's) fear that we could destroy all of life is fueled by the same hubris that has gotten us into this predicament in the first place. It is a pity that humanity's crowning accomplishment will be the first mass extinction event caused by a life form.

[Shared Humanity]

There is another (perhaps more enlightening) way to look at the 80,000 year time frame for the Permian extinction event.

Humanity is focused on a very short time frame when compared to geologic time. We live our lives primarily in units of time marked by generations. The average human lifespan is three generations. As adults, we worry about the fates of our children and grandchildren. The more introspective may have concerns that embrace longer time frames but their are precious few of these. The least enlightened are preoccupied with whether they dine out at Applebees or Chi-Chi's this Friday.

Interestingly, Native Americans had expanded this sense of responsibility. They had a well established "seventh generation" concept that informed their decisions and choices. Every decision was made with a sense of respect of the seven generations that preceded them and a concern for the impact of the seven generations that would follow. We would be well served if we could consider such a philosophy.

Back to the 80,000 year long extinction event. Given humanity's impact on other life forms which have been documented by science, it could be argued that we are a good 20,000 years into this event, perhaps 30,000. We cannot see this because we live our lives on such a limited time frame. 200 years is history. 5000 years is ancient history. There is really no true natural environment (untouched by man) left on this planet. Wherever we have gone, other life forms have suffered and many have been driven to extinction. The pace of this extinction event is accelerating rapidly and, with the exception of some well publicized extinctions or approaching extinctions which capture our imagination (Pandas, leopards etc.), goes largely unnoticed. For example, how many of us are aware of the dramatic drops in phytoplankton levels across the planet's seas and oceans?

Early in humanity's history, our impact was regional. In North America, large mammals were driven to extinction through hunting over several thousand years after we got here. The Aborigine caused a similar extinction in Australia. We now have begun to drive extinction globally as we cut down forests, cause the acidification of the oceans and dump CO2 into our atmosphere. We are like the Siberian Traps. The only real difference is that humanity's ingenuity is bringing this extinction event more rapidly.

[Dromicosuchus]

...My apologies for butting in with this not-terribly-helpful and kinda pedantic post, but it could be argued, Shared Humanity, that we actually aren't the first lifeform to have brought about a mass extinction on Earth.  The transition from a reducing to an oxidizing atmosphere, brought about by the prodigious success of cyanobacteria, must have been absolutely devastating to the life existing on the time--likely far worse, in its way, than any of the Big Five. 

...Of course, since the only victims of the Oxygen Poisoning were bacteria and archaea, the event generally doesn't get quite as much attention as the more dramatic extinctions.  Still, it's humbling to realize that even in our role as mass executioners we were preempted--and, humiliatingly, we weren't preempted by some impressive ur-predator, but by greenish-blue slime.

[dorlomin]

We face a likely 3C increase per doubling of preindustrial CO2.

This will be pretty bad news for a large number of people. But there is little to nothing to suggest the earth turning into Venus or even something like the Permian extinction, a very complex event 250 odd million years ago that we little understand.

As I have said there are a number of negative feedbacks that are real and have worked in the past. There are many 'hyperthermals' in the past such as during the Eocene, Toarcian and Apatian etc etc.

During some of these events sea temperatures may have reached 38C, yet the weathering of the rocks , draw down of biological matter into anoxic zones and other sequestering mechanism brought the climate back to stability.

It is likely that the warmest the planet has been in the past 2 billion years would have been when one of the super ice house earths came to an end. During the Cryogenian.

At the moment we are only headed to around 450ppm or recreating the kind of climate we had in the Pliocene.

Best focus on making sure we dont go beyond that. 

[Lucas Durand]

Still, it's humbling to realize that even in our role as mass executioners we were preempted--and, humiliatingly, we weren't preempted by some impressive ur-predator, but by greenish-blue slime.

I try not to think about what might happen so far down the road, but speaking of bacteria...

I wonder what others think of the plausibility that a possible "really bad case scenario" for the future is a return of bacteria as the dominant life form on this planet:


Maybe it's just because my well water sometimes smells like rotten eggs that I can imagine all those anaerobic bacteria "lurking" on the fringe - just waiting for the conditions to be right to make a [humbling] comeback.

Or maybe its that the oceans are warming...

Anyway, seems plausible and terrible.

[Glenn Tamblyn]

Lucas

Hard to imagine the anaerobic bacteria making a big comeback. To many cyanobacteria that keep filling the air with oxygen.

When you think about it, all the research being spent on looking for earth like planets around other stars is ultimately focused on looking for planets that have cyanobacteria.

Perhaps SETI should be refocused. SETC The Search for Extra-Terrestrial Cyanobacteria.

[Anonymouse]

Hi Shared Humanity,
I appreciate your optimism and I think your philosophical approach is useful for keeping one from beating one's head against the wall.  Nonetheless, I read Hansen's "Storms" and unfortunately the last few chapters seem to line up all too well with this admittedly apocalyptic essay from Arctic News (I have no idea how credible they are but read anyway with a grain of salt) http://arctic-news.blogspot.com/2013/03/the-worst-case-and-unfortunately-looking-almost-certain-to-happen-scenario.html. 
I also understand the point Dorlomin is trying to make about rock weathering and negative feedbacks, however the only rebuttal I have is to reiterate that the speed of our current warming is unprecedented, as far as I am aware.  In the past, warming processes seem to have taken much longer, which would seem to mean that earth's negative feedbacks had much more time to maintain some kind of foothold in keeping that warming in check.  I am not convinced that is the case today, especially with our current state of uncertainty about the positive feedbacks such as methane and how they interact.
Cheers all, and thanks for the conversation.

[fishmahboi]

Hi Shared Humanity,
I appreciate your optimism and I think your philisophical approach is useful for keeping one from beating one's head against the wall.  Nonetheless, I read Hansen's "Storms" and unfortunately the last few chapters seem to line up all too well with this admittedly apocalyptic essay from Arctic News (I have no idea how credible they are but read anyway with a grain of salt) http://arctic-news.blogspot.com/2013/03/the-worst-case-and-unfortunately-looking-almost-certain-to-happen-scenario.html. 
I also understand the point Dorlomin is trying to make about rock weathering and negative feedbacks, however the only rebuttal I have is to reiterate that the speed of our current warming is unprecedented, as far as I am aware.  In the past, warming processes seem to have taken much longer, which would seem to mean that earth's negative feedbacks had much more time to maintain some kind of foothold in keeping that warming in check.  I am not convinced that is the case today, especially with our current state of uncertainty about the positive feedbacks such as methane and how they interact.
Cheers all, and thanks for the conversation.

I posted the same link earlier and I would like to note that it is difficult to judge the link as something definitive for the bleak future that is in store for earth, especially if one looks to the comments section, as there is little evidence actually presented in the blog to support its outlook.

You've said a lot in this blog post, but is any of it other than pure speculation? You have not provided evidence of anything you have written. Don't you have any?

[Anonymouse]

Hi All,
Sorry for the broken link, if you are interested in this article on Arctic News go directly to the source and scroll down. Or just use the google, etc. It is not a published paper, merely a great essay.

[dorlomin]

reiterate that the speed of our current warming is unprecedented, as far as I am aware.  In the past, warming processes seem to have taken much longer,

Once you go beyond the ice cores, resolution on temperature becomes very low. And the deeper we go back in time the grainyer it gets. I am not sure at where things are at the moment but even a few years ago, refining the resolution to 10 million years for the Ordovocian temperature\ CO2 was seen as an achievement.

There have been many events that may have seen some pretty rapid climate changes.

The hypothesised warming after the KT bolide, the ending of one of the Cryogenian’s super ice ages? Other factors such as past rapid climate changes having come from a much higher base, i.e. 3 or 4C warmer than today.  The fact that the earth has been 8C warmer than today without a runaway happening.

Some points to ponder.
-   The Himalayas\ Tibetan Plataea  are our guardian angel here. They are unusually high and covering a huge area and near the tropics. This means that a huge amount of rock is available for weathering where it rains a lot.
-   The hotter it gets the more it rains, the more CO2 there is the more acidic the rain… the faster the weathering.
-   We have been as warm as today for thousands of years in the recent past (about 7000 years ago) without triggering anything dangerous. So we are still within safe thresholds.
-   We have been about 1C warmer than today just 120 000 years ago without anything dangerous having happened so we are unlikely to have triggered any dangerous threasholds.
-   CO2’s impact is logarithmic. So get have the same effect you need to have double the amount. This means past climate changes need huge amounts of CO2 for small changes. The mid Cretaceous for example had about 2000ppm so would have needed another 2000ppm for a 3C change (rough estimate).
The runaway greenhouse was a very big thing in the 70s in science. Hansen, Sagan and many of the others were people who had studied Venus and were very worried about the same thing happening here. But as our knowledge has improved the likelihood has receded. The hotter it gets the more there is working to get the CO2 out of the atmosphere and the exponentially increasing amounts of CO2 it will take to keep getting warmer.

The current warming is hugely damaging to the people of the world and poses huge risks. Runaway warming is very low down the list of those risks.

[dorlomin]

Stephen Schnieder on the complexity of climate change.

[Anonymouse]

Hi Dorlomin,
I agree with all the points you post.  YES.  Weathering and all of the stuff we as humans have been able to quantify and count on exist.  But I still am not convinced we are not into something we have never, ever, ever seen before.  I would love for you to be right, but I am not convinced.  You make very compelling points, you are passionate and obviously educated in this subject, but I am still not convinced.
If earth heads into Venus Syndrome, I don't think it will happen in the next ten years, maybe not even the next 100 (I reserve my bets because of methane release).  But the lead-up into that, well, that may happen in my lifetime.  Overall, with this latest Arctic eggshell breaking, I am betting on chaos.  Because the civilization we live in assumes that rock weathering happens in less than 3 years, while you know very well it takes 10's of thousands, at best.  Timescale is key.

P.S. Don't disregard Hansen.  He knows his stuff.
Again, TIMESCALE.

[dorlomin]

But I still am not convinced we are not into something we have never, ever, ever seen before.

You are entitled to an opinion, however when assessing risks we need to look at facts.
We have nearly the lowest levels of CO2 in the planets history.
CO2s impact is logarithmic, that is it takes double to have the same impact each time.
We are starting from an actual ice age.

We are starting much deeper in the well than other climate changes. And as I said we have an enormous buffer in the Himalayas that other climate regimes may not have had.

Whats more, while it has a long tale, CO2 also does quickly drop. In about 40 years it drops in half.



This brings us to another two points. There are limits to how much fossil fuel we have and the oceans are huge.

It takes a very long time to warm them up.

Many past climate changes were from vulcanisity. These were events that lasted thousands and tens of thousands of years.

This was a long long time to warm up the oceans.

Even in a burn it all scenario our emissions will start coming down in a couple of decades from just not having anything left to burn.

It is possible you can devise a scenario where we burn so much so fast that it does release all the carbon sequestered in the oceans methane, and perhaps we do get the oceans hot enough to release the calcium carbonate etc and it does over come the rock weather etc etc etc. But you will need to show real studies, showing how this can happen.

But simply worrying about it is not really going to cut the mustard in convincing many who understand just how much energy it takes to heat an ocean.

Some thresholds that all would consider dangerous have no support in the literature
as having a non-negligible chance of occurring. For instance, a “runaway greenhouse effect”—analogous to Venus--
appears to have virtually no chance of being induced by anthropogenic activities. So our focus will be on those events
that the literature suggests have a non-negligible chance of being induced by anthropogenic activities.

IPCC

I reserve my bets because of methane release.....Timescale is key.

Most of the methane is sequestered deep in the oceans. It has been released before when the earth was much hotter to start with. It took a long time for past CO2 levels to set it off.

By the time our heat pulse is getting into the deep ocean our carbon stores will have long been burned and the CO2 dropping. Also methane is released and quickly breaks down.

World expert on carbon cycles, David Archer calculated the worst case scenario for Arctic methane.

Let’s err on the side of flamboyance (great word in this context) and say the concentration of methane in the air goes up by a factor of 10 for the duration of the extra methane emission (meaning that the lifetime doubles).

This is about twice the radiative forcing today from all anthropogenic greenhouse gases today, or (again according to Modtran) it would translate to an equivalent CO2 at today’s methane concentration of about 750 ppm. That seems significant, for sure.

http://www.realclimate.org/index.php/archives/2012/01/an-arctic-methane-worst-case-scenario/#more-10411

It takes a lot of ifs, but, ands and hand waving to get that methane to the atmosphere quickly. Then when its there it would be disastrous... but nowhere near Venus Syndrome.

P.S. Don't disregard Hansen.  He knows his stuff.

I wasnt, merely pointing out that he, Sagan, Ramanathan and Lovelock all started (in terms of getting into climate issues) out as planetary scientists.

[Shared Humanity]

 <i>Also methane is released and quickly breaks down. </i>

Methane does break down but the process is one of oxidation resulting in one CO2 molecule and two water molecules. How does this figure in?

[dorlomin]

<i>Also methane is released and quickly breaks down. </i>

Methane does break down but the process is one of oxidation resulting in one CO2 molecule and two water molecules. How does this figure in?

It is the CO2 that causes all the damage. While the initial drop off is quick, it has a 'long tail'. 

. The models agree that 20–
35% of the CO2 remains in the atmosphere after equilibration with the ocean
(2–20 centuries). Neutralization by CaCO3
draws the airborne fraction down
further on timescales of 3 to 7 ky

Link

It accumulates as the methane is released and breaks down, slowly doing its thing. Warming the oceans and the world.

One of the hardest things in communicating to people about climate change is the long tail of CO2 and the slowness of ocean response. It is like a gigantic leviathan that moves slowly but with so much power for even small shifts.

[fishmahboi]

Living Life on the edge - earth on the edge of Runaway Global Warming, habitability zone.

http://arctic-news.blogspot.ie/2013/04/earth-is-on-the-edge-of-runaway-warming.html

Kopparapu calculates that the Solar System’s habitable zone lies between 0.99 AU (92 million mi, 148 million km) and 1.70 AU (158 million mi, 254 million km) from the Sun. In other words, Earth is on the edge of runaway warming.

[Lennart van der Linde]

Jim Hansen doesn't think the Venus Syndrome is possible anymore (he did in his book 'Storms of my Grandchildren'), for the coming billion years at least:
http://www.columbia.edu/~jeh1/mailings/2013/20130415_Exaggerations.pdf

Also see his newest article in press, which further explains his position on the Venus Syndrome (on pp.17 and 23-24):
http://arxiv.org/abs/1211.4846

A hothouse (largely) unfit for humans to live in is still possible, however, according to Hansen c.s.

[Lennart van der Linde]

See especially this quote from his latest communication to the public:
'At least one sentence in "Storms" will need to be corrected in the next edition: even with burning of all fossil fuels the tropical ocean does not "boil". But it is not an exaggeration to suggest, based on best available scientific evidence, that burning all fossil fuels could result in the planet being not only ice-free but human-free.'